PREPARATION AND CHARACTERIZATION OF ION EXCHANGE MATERIALS AND THEIR USES IN

IDENTIFICATION AND DETERMINATION OF COMPOUNDS

ABSTRACT

THESIS SUBMITTED FOR THE DEGREE OF

Bottor of l^liilaisioptip

CHEMISTRY

BY

RASHEED MOHD. JAMHOUR

DEPARTMENT OF CHEMISTRY ALIGARH MUSLIM UNIVERSITY

ALIGARH (INDIA)

1996

This thesis comprises of five chapters. In

the first chapter, a detailed and uptodate review of

literature on the subject has been cited. The

synthetic inorganic ion-exchangers of two component

system have now been well established. However,

these materials are widely used in many

applications, in particular where chemically

modified oxide surfaces are involved. Indeed, in

disciplines such as separation of ionic components

in radioactive wastes and as catalysis where ion-

exchangers are very much helpful due to their

resistance to heat and radiation. In all cases, the

knowledge of their chemical and surface

characteristics is of great importance for the

understanding and eventual improvement of their

performance. For that, three-components ion-

exchangers have been studied and found to have

higher ion-exchange capacities and more selective

than simple salt ion-exchangers. Inorganic ion-

exchange materials also have an analytical potential

for the recovery and concentration of strongly

absorbed trace constituents which has made their

study more interesting. They can be prepared, in

general, as gelatenous precipitate by mixing the

li

oxides of group IV to more acidic oxides of groups

V or VI of the periodic table. Sometimes, refluxlng or

changing the conditions of preparation Is

recommended to improve the reproducibility and ion-

exchange characteristics.

Chapter two describes the synthesis of

zirconium(IV) oxide-ethanolamine exchanger which is

prepared by mixing an equimolar/nonequimolar

solutions of zirconium oxychloride and ethanolamine

in different ratios (V/V) under varying conditions

of mixing, pH and reflux time. The action of

ethanolamine was to hydrolyse the zirconium(IV)

salt, and then to get adsorbed onto the surface of

fresh hydrous zirconium{ IV) oxide. The pH of the

mother liquer was adjusted by dropwise addition of a

dilute hydrochloric acid in order to produce a

favourable environment for the hydrolysis. The

framework of the gel has been found to show

amphoteric character. The hydrolysis and

polymarization of zirconium salt appears to produce

networks with -0-Zr-O bridges which are cross-linked

on alternate zirconium atom. A preliminary

investigation to this effect has been carried out

using Fourier-transform infrared spectroscopy

lii

(FT-IR), X-ray diffraction (XRD), thermogravimetry

(TG), and differential thermal analysis (DTA).

Further the analytical studies show that this

material has both catlonic and anionic properties

supporting the above statements. One of the samples

of zirconium{IV) oxide-ethanolamine (ZEA-3) has been

studied in detail due to its maximum ion-exchange

capacity and chemical stability. Distribution

coefficient values (kd) of a number of anions and

metal ions on zirconium(IV) oxide-ethanolamine in

different solvent systems have been determined. As a

result of the difference in their Kd values some

useful separations of anionic species have been

successfully achieved using column chromatography.

In the third chapter a new approach has been

made on the use of zirconium phosphate ion-exchanger

to serve as coating material in thin-layer chromato­

graphy (TLC), to separate carbamate pesticides and

related compounds. To resolve carbaryl, carbendazim,

carbofuran, mancozeb, phenol, 4-chlorophenol,

o-nitrophenol, tf-naphthol and p-naphthol various

solvent systems have been tried. The R values

obtained on ZrP plates are compared with those

obtained on silica gel G layers which showed

Iv

improved results. The R. values obtained on

zirconium phosphate plates are discussed in terms of

polarity of different solvents and their ratios of

mixing with each other. It has been observed that a

systematic increase/decrease in R. or a complete

retention of the compounds taking place on zirconium

phosphate layers depending upon the solvent system.

In addition, the interaction of pesticides with

zirconium phosphate has been taken into account of

physical forces.

In the fourth chapter, we describe the

preparation of layered double hydroxide of Al(III)

Mg(II)-carbonates and the behaviour of guest

molecules e.g. sulfamic acid and dodecylamine.

Layered double-hydroxides (LDHs) has been

synthesized by mixing the nitrate salts of Al(III) 8

Mg (11) with sodium hydroxide and sodium carbonate

solutions over a period of 1 hour. The preparation

of the host material was done by calcinating the

Al(III) Mg(II)-carben.ate at 450±10° in air for 6

hours. After calcination, solution of sulfamic acid/

dodecylamine was added to the material and kept on

stirring for 3 days. The intercalation of guest

molecules are examined by X-ray diffraction, FT-IR,

thermogravimetry (TG), and differential thermal

analysis (DTA). The results of the above studies

showed the intercalation of dodecylamine and

sulfamic acid with LDH. Moreover the LDH-dodecyl-

amine intercalation compound exhibits remarkable

complexing behaviour for transition metal ions

illustrated by sorption capacities and the pH-titra-

t ions.

The fifth and last chapter describes the

thin-layer chromatographic (TLC) behaviour of some

cephalosporin antibiotics on layered double

hydroxides-silica gel mixed layers as coating

material. The (LDH) coating material possess

exchange capability for both organic and inorganic

anions. The framework consists of pi 1lared-like

2-structure, in which anions such as C0_ and water

occupy interlayer space and can be exchanged by

organic neutral or anionic species. The cephalo­

sporin compounds in buffer system may acquire a

negative/positive charge and can act as neutral

spiecies. Moreover, the silica gel surface provides

the physical interaction during the development of

compounds. The R. values were obtained with the use

of eighteen various mobile phases. The use of the

vi

mixed layers gave an improved results compared with

silica gel only. In addition, considerable movement

of molecules with compact spots has been observed.

Furthermore, the results were described according to

the 1ipophilic/lipophobic nature of the cephalo­

sporins studied. The R. values were examined on

changing the composition of the mobile phase and by

varying the methanol concentration in the mobile

phase. As a result the R._ , i i ^ j ^ Ml values were calculated

for each compound, and ploted against the

composition of the mobile phases.

PREPARATION AND CHARACTERIZATION OF ION EXCHANGE MATERIALS AND THEIR USES IN

IDENTIFICATION AND DETERMINATION OF COMPOUNDS

THESIS SUBMITTED FOR THE DEGREE OF

Bottar of $I)tlo£iopt)P

CHEMISTRY

BY

RASHEED MOHD. JAMHOUR

DEPARTMENT OF CHEMISTRY ALIGARH MUSLIM UNIVERSITY

ALIGARH (INDIA)

1996

\f ^ '

- ^ ^ ^

\<v No .

• : 1 T,.s&133T

T4812

'^^^-^l

s:

0^0 tht

Memory of my

FATHER

SAIDUL ZAFAR QURESHI M.Sc.,Ph.D.,C.Chem. MRIC(London)

Professor of Analytical Chemistrv

Phone f Off.

1 Res

0571-25515

0571-20724

Department of Chemistry Aligarh Muslim University

Aligarh-202002 (INDIA)

Date

This is to certify that the thesis entitled

"Preparation and Characterization of Ion Exchange

Materials and Their Uses in Identification and

Determination of Compounds" is the or ig ina l research

work of Mr. Rasheed Mohd. Abdel-Qader Jamhour and is

sui table for submission for the degree of Doctor of

Philosophy in Chemistry.

^ ^ V ' : ^ (SAIDUL iZfAEAR QURESHI)

Supervisor

A CKNO WLEDGEMENT

If Is a pnvlk'gc to express my sensihilit}- and gratitude to my sage supenisor p}X)fcssorSaidulZafarQuivshi, Department ofChemistiy, AligarhMuslim University, for his inestimable guidance. His pertinacious efforts, humility and honesty made this work progressive.

I am grate fid to Professor Nund Islam, Chairman, Department ofChemistiy, for providing laboratoiy faciUties.

I extend my thanks to Dr Nafisur Rahman for his immense help and affirmative response. His expert opinion was a boon for the success of this work. I also take this opportunity to thank my colleagues and friends, Mr Murad Izzat, Mr. R. Khayer, Mr Eyad Samih, Dr Irshad, Dr. (Miss) Ghazia and Dr (Mrs) Soofia, who have been spurring me to get a smooth success throughout the tenure of this project.

It is my pleasure to express my unfathomable sensation andthanks to Mrs. Rita and Dr. C.N. Kuchroo. They stood with me in adversity! and prosperity without any hesitation. I am extremely auspicious of their invigorative encouragements and hoping to reciprocate in excellent paths.

With due reverences, I am cordially enthusiastic to thank my loving parents, brothers and sisters. Their continuous endeavour, strive, prudence and blessings made the lucrative triumph in my academic pursuit and blooming future.

At last, I believe that whatever I achieved in my academic career is the result of God's blessings.

(RasheedM/A.Q. Jamhour)

CONTENTS

Page No. CHAPTER ONE

General Introduction 01 References 27

CHAPTER TWO Surface Interaction of Ethanolamine with Hydrous Zirconium(IV) Oxide Gel: Characterization and Separation of Anionic Species by Column Chromatography 40

CHAPTER THREE Thin-Layer Chromatographic Behaviour of Carbamate Pesticides and Related Compounds on Zirconium Phosphate Layers. 66

CHAPTER FOUR Preparation and Charactenzation of Layered Double Hydroxides and Intercalation Behaviour of Sulfamic Acid And Dodecylamine 86

CHAPTER FIVE Novel Thin-Layer Chromatographic System: identification and Separation of some Cephalosporins on Layered Double Hydroxides-Silica Gel Mixed Layers. 108

LIST OF PUBLICATIONS ^27

LIST OF TABLES

PAGE NO.

50

60

62

63

TABLE 1.1 Synthesis and properties of two-component inorganic Ion-exchangers. 12*18

TABLE 1.2 Properties of three-component ion-exchange mater ia l s . 19-2 3

TABLE 2.1 Synthesis of Zr(IV) oxide-ethanolamine under varying conditions. 49

TABLE 2.2 Chemical s t ab i l i ty of ZEA-3 in various solvent!systems.

TABLE 2.3 Distribution coefficient of some anions on ZEA-3 in DMW and varying cone, of NH NO,.

TABLE 2.4 Distribution coefficient of metal ions on ZEA-3 in DMW and at different pH range (3.72-6.00) .

TABLE 2.5 Separation of anions achieved on ZEA-3 exchanger .

TABLE 3.1 R values of carbamates and re la ted • compounds together with the composition of the mobile phases studied on ZrP-TLC pla tes . 47-77

TABLE 3.2 R values of carbamates and re la ted

compounds on silica gel G p la tes . 78-79

TABLE 3.3 Separation achieved using different solvents on zirconium phosphate gel as coating material on TLC pla tes . 80-81

TABLE 4.1 X-ray diffraction data of s t a r t ing LDH. 93

TABLE 4.2 X-ray diffraction data of LDH-sulfamic acid in tercala t ion compound. 94

TABLE 4.3 X-ray diffraction data of LDH-dodecylamin in tercala t ion compound. 95

TABLE 4.4 Sorption capaci ty of some metal ions on LDH-amlne intercalat ion compounds. 104

TABLE 5.1 R values of cephalosporins on LDH-sillca gel plates and the composition of the solvent systems, 117

TABLE 5.2 The mean of the R values together with their s t anda rd e i ror . 118

LIST OF FIGURES

PAGE NO.

FIGURE 2.1

FIGURE 2.2

FIGURE 2.3

FIGURE 2.4

FIGURE 3.1

FIGURE 4.1

FIGURE 4.2

FIGURE 4.3

FIGURE 4.4

FIGURE 4.5

FIGURE 4.6

FIGURE 5.1

FIGURE 5.2

IR-spectra of zirconium oxide and pure ethanolamine

FT-TR spectrum of zirconium(IV) oxlde-ethanolamine exchanger .

Thermogram of zirconium(iy) oxlde^ ethanolamine.

Structure and mechanism of prepara t ion of ZEA exchanger.

Solvent polarity agains t the R values of carbamate pesticides and r e l a t e a compounds.

X-ray diffractogram of LDH-s tar t ing, LDH-sulfamic acid and LDH-dodecylamine.

FT-IR spectrum of s t a r t i ng layered double hydroxides (LDH).

FT-IR spectrum of LDH-sulfamlc acid.

FT-IR spectrum of LDH-dodecylamine

Thermogram of LDH-sulfamlc ac id .

pH-tltratlon curves of LDH-amlne in terca­lat ion compound.

R. values of cephalosporins aga ins t the composition of the mobile phases .

R . values of cephalosporins aga ins t the composition of the mobile phases .

53

55

57

59

82

92

97

99

101

102

105

120

121

GENERAL INTRODUCTION

Every respectable branch of science bas Its own

theory- a collection of laws, axioms, corollaries, and

rules that guides the scientist in using experiments to

unravel the secrets of nature. Analytical chemistry is

a discipline in its own right in chemistry. It has an

extensive applications in the analysis of organic

compounds, pharmaceuticals, biochemicals, bodyfluids,

polluted water, foods, solids, and in many other areas.

This branch of chemistry usually begins by placing

chemical analysis in the broader prespective of

chemical sciences, describing different types of

analysis e.g., qualitative, semiqualitative and

quantitative on macro, semimicro and micro scale. No

doubt, analytical chemistry has covered a long and

complicated path of development, however, for the last

few decades, it witnessed a substantial expansion of

range of objects being studied, among which an

important place is now occupied by rare and artificial

radioactive elements.

The realm of analytical chemistry is widening

day by day with the modern sophisticated instrumenta­

tion techniques which made it possible to elucidate the

microstructure of molecular species and to obtain and

Identify the substance in the highest state of purity.

Undoubtedly, significant factor that has been the rapid

development in electronics, particularly noticeable

has been the explosive evolution of electronic digital

computer in its various forms* Despite the changes that

have taken place over the years, the goals and

objectives of chemical analysis have not changed. What

has changed are the ways in which these objectives are

realised.

Besides chemical methods, fractional precipita­

tion, distillation, and crystallisation have been

extensively used for separation and purification of

chemical compounds. However, chromatography plays a

very important and significant role in solving many

problems related to identifiction, separation and

quantitative determination of ionic and non ionic

species. The chromatographic technique was developed by

Tswett in 1906, who applied it to the separation of

coloured substances using finely divided CaCO» as

adsorbent. The utilization of chromatographic technique

in 1931 for the resolution of complex organic mixtures

awakened the scientific world to its almost unlimited

possibilities. Nowadays, its use not only restricted in

dealing the problems of organic chemistry but also in

every field of science related to chemical analysis.

The term chromatography is applied to a variety of

techniques which are similar iri many .respects, but

differ greatly in the principles on which they are

based, for example, we have the high performance liquid

chromatography (HPLC), gas chromatography (GC), ion-

exchange chromatography, thin-layer chromatography

(TLC), and high performance thin-layer chromatography

(HPTLC). Amongst all the chromatographic techniques,

ion-exchange chromatography is considered to be very

versatile technique particularly in the separation of

rare earths and other metal ions which differ in their

sorptivity. It has proved to be an excellent tool to

give an accurate determination of industrial effluents,

alloys with multi components, pharmaceuticals,

biological substances and fission products of

radioactive elements.

The other distinguished chromatographic

technique is TLC where advances in the theoretical

interpretation, modernization of technique, and

diversified applications continued to rise. Like the

other techniques, most of its applications are

concerned with drug formulations, pharmaceutical

preparations and lipid analysis, in addition to the

analysis of amino acids, bases, steroids, pesticides

toxins, and inorganics using TLC and HPTLC techniques.

Some of the coating materials -which have been used

successfully are silica gel and chitin layers used for

separation of amino acids (1), 50% silica and 50% C_ o

bonded-silica used for the 2-D separation of lipophilic

and hydrophilic dyes (2), pharmaceuticals are separated

on layers of barium sulfate (3), layers of NaX

molecular sieves used for cation separations (4),

commercial chiral plates [C^Q layers dipped into cupric 1 o

acetate and a solution of chiral (2S, 4R, 2'RS)-4-

hydroxy-(2'-hydroxydodecyl)proline] used for the

separation of amino acids and 3-thiazalidine-4-carboxy-

lic acid (5,6), metal ions are separated on c6rium{IV)

antimonate {7) and tin(IV) arsenosi1icate and arseno-

phosphate (8) layers.

Separation and identification is one of the

most promising subject of analytical chemistry to get a

better insight into the nature of the matter. The

resolution of a complicated mixture into its compounds

and subsequent determination can be achieved both by

instrumental and non-instrumental techniques. Indeed,

ion exchange chromatography has broadened the spectrum

of the subject, making many difficult separations

possible. Ion-exchange, from the dayof its discovery., has

added a shining spark in the field of analytical

chemistry.

The phenomenon of ion exchange process was

first described by Thompson (9). and Way (10)

independently. The ion-exchange phenomenon was also

observed in naturally occurring zeolites which were

found to have aluminosilicate structure (11). The

zeolite minerals which include Analcite Na[Si„A10_]

2H2O, Chabazite (Ca, Na) [Si2AlOg]6H20, Harmotome

(K.Ba) [Si5A10g]2.5H20, and Natrolite Na2[Si3Al20^Q]

2H 0 which have an open three dimensional framework.

These materials were successfully used as molecular

sieves. However, due to certain limitations, their

place was taken by synthetic available aluminosi1icates

with improved properties. Folin and Bell (12) made the

first application of synthetic zeolite for the

collection and separation of ammonia from urine. Thus,

the early ion exchange materials synthesized were

largely inorganic in nature. Later on, synthetic sodium

aluminosilicate, Na^A^SioO^Q found application in

cation exchange process which was developed by Cans

(13).. Nowadays, zeolites find applications as

catalysts alongwith transition metal ions in the

synthesis of many organic compounds (14).

During the last two decades the inorganic ion

exchangers have firmly proved to have their own

position among the ion-exchange, materials. The rapid

development in nuclear energy, hydrometallurgy of rare

elements, preparation of high purity materials, water

purification etc., has enforced attempts to find and

synthesize highly selective ion exchangers having more

convenient properties than zeolites or otherwise. The

renowned workers in this field of synthetic inorganic

ion exchangers are Kraus (15,16), Amphlett (17-19),

Pekarek and Vesley (20), Clearfield (21,22), Alberti

(23,24), Walton (25-28) and Vol'Khim (29) etc., who put

significant contribution dealing different aspects of

these materials other than the ion exchange properties.

Qureshi and Coworkers (30) prepared a large number of

inorganic ion exchange materials and characterized them

with respect to their structural configuration, heat

treatment, distribution coefficients of ionic and non

ionic species etc., and applied them to separation

studies.

Synthetic inorganic ion exchangers have been

Classified into the following main groups :

1. Hydrous oxides and insoluble salts

2. Quadrivalent metal oxides (oxides of group IV with

more acidic oxides of groups V and VI of the

periodic table).

3. Synthetic aluminosilicates

4. Salts of heteropoly acids

5. Double layered hydroxides

The term "hydrous oxide" has been used in its

widest sense to refer to insoluble materials with a

metal oxide-water system. A wide range of hydrous

oxides exhibit excellent selectivity with respect to

certain elements or group of elements due to their

amphoteric nature. Indeed, the higher oxides of metals,

such as the hydrous oxides of Nb, Ta, Sb(V), Mo(vr).

and W(VI) exhibit cation exchange properties and show

little or no anion exchange character even in acidic

solution. On the other hand, hydrous oxides of Mg, La,

and Bi exhibit only anion exchange properties and

little cation exchange behaviour even at high pH of 12.

Hence, amphoteric ion exchangers are found mainly among

the hydrous oxide of ter- and quadrivalent metals.

Amphoteric exchange reaction can be deduced by the

following dissociation reaction,

Anion exchange reaction : M-OH ,. M + OH"

(Reverse reaction)

Cation exchange reaction c. l-OH '••— M-0~ + H

(M-represents the central metal atom)

Several reviews on the inorganic ion exchange

properties of oxides and hydrous oxides have been

published (31,32). Some of its application have been

the work of Girandi etal. (.33,34);, who very successfully

used hydrous antimonic(V) oxide in neutron activation

analysis practice for separation of Na from the

investigated sample. In addition to this, a large

number of papers have been reported recently on the

subject with particular attention to a deeper knowledge

of the adsorption mechanism as well as their

application in various fields of interest. Most insoluble

hydrous oxides can exist in a number of forms with

different chemical and physical properties, depending

on their methods of preparation and subsequent

treatment. Almost all cations of valency 3 or higher

gave rise to polynuclear species in aqueous solution

over an appropriate pH range. For example, the

different hydrolyzed species of zirconium ZrOOH ,

[(ZrO)3(OH)g]*^, and [ (ZrO)^ (OH)^ l"*" have been observed

depending upon the pH of mother liquor.

9

Inorganic ion exchangers of the acidic salts of

multivalent metals are produced by mixing the acidic

oxides of the metals belonging to group IV to more

acidic oxides of group V and VI of the periodic table

which result in the production of insoluble white

gelatinous material. Their composition is

non-stoichioraetric and depends on the conditions under

which they are precipitated. The materials which have

so far been synthesized include: M(IV) - phosphate,

arsenate, molybdate, tungstate, silicate, vanadate, and

tellurate etc. where M(IV) stands for Zr(IV), Sn(IV),

Ti(IV) etc. Recently, these materials have found

potential applications in many other areas such as

hydrogen-oxygen fuel cell, desalination process and

artificial kidney machines to remove ammonium ions

(3S).

Heteropoly acid salts have also been of

interest. A number of compounds have been prepared

belonging to the class of 12-heteropoly acids having

the general formula H^XY^^O^Q'^H^O, where x may be one

of the several elements including phosphorus, arsenic

and silicon, and Y a different element such as

molybdenum, tungsten, and vanadium. The heteropoly

compounds especially those of 12-molybdo compounds are

quite strong oxidizing agents.

10

Some of the acid salts of tetravalent metals

have been found to have a layered structure (CC-layered

materials). The. most pertinent example of this type of

material is OC-zirconium monbhydrogen phosphate (cc-ZrP) .

The oc-iayered materials have been generally prepared

by refluxing the amorphous materials in concentrated

phosphoric acid (10 to 14 M) for a few days (19, 21,

36, 37). As in the case of cC-ZrP, the degree of

crystallinity increases with increase of the refluxing

time and of the concentration of phosphoric acid. The

structure is layered and consist of a sheet of roughly

coplanar Zr atoms sandwiched between two sheets of

monohydrogen phosphate group. Each zirconium atom is

coordinated octahedrally to 6 oxygen atoms. Each of

these 6 oxygen atoms belongs to one of six different

monohydrogen phosphate group. The forces between the

layers are very weak hydrogen bonds or Van der Waals

forces and the inter layer distance is 0.76 nm. The

layers are arranged relative to each other in such a

way that the zirconium atoms in one layer lie over the

the P atoms in an adjacent layer and vice versa. A

water molecule resides in the centre of each cavity and

is hydrogen bounded to phosphate groups. The structural

features of the p-phase of zirconium phosphate are

essentially the same as those of oc-ZrP but the

11

difference is that the interlayer distance in this case

is 0.928 nm. The layer packing sequence is such that

neighbouring HPO, groups from adjacent layers are

aligned opposite to one another to allow interlayer

hydrogen bonds of the type O P — 0 0 — PO . The struc-

ture of oc-ZrP is very closely related to that of

p-ZrP. The interlayer distance is larger than that of

p-ZrP (38). The roost important two-component ion-

exchange materials investigated are reported in (Table

1.1).

It has been found that mixed salts of three-

components system possess better ion-exchange

properties compared to simple salts or two-component

ion-exchangers. They show superiority over simple salts

in terms of their (i) stability towards thermal and

chemical treatment, (ii) high selectivity (iii)

increasing capacity. A review on three-component ion

exchange materials has been summarized in (Table 1.2).

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24

An Important c lass of layered materials are the layered

double hydroxides with general formula

I M J ^ M " ' ^ ( O H ) - ] ' ^ ' ' X" Z H „ 0 1-x 2' x-n 2

where M^^ = Mg^*, Mn^*, Fe^*, Co^*, Nl^*, Cu^*, Zn^* or Ca^*

. . I I I .,3+ ^ 3+ . . 3+ „ 3+ „ 3+ _ 3+ ,2+ , 3+ M = Al , Cr , Mn , Fe , Co , Sc , \ r or La

and X~ is the balancing anion. In i t s s t ructure some of the

M(II) ions of hydroxide layer (M (OH)^) are replaced by M(III)

ions, and the total charge of the l ayer becomes positive. The

inorganic anion x ' is exchangeable by other inorganic and

organic anions (183). One reason for the importance of this c lass

of compounds Is that they are the only intercrysta l l ine-react ive

layered mater ia ls consisting of posi t ively charged layers which

can act as anion exchanger. They can also serve as models of

the binding of anionic surface active agents on solid surfaces

(184).

The use of various novel inorganic exchangers s t i l l

commands attention but few have been commercialized, especially

in HPLC par t ic le sizes. Among these described are titanium

dioxide (185), titanium phosphate (186), titanium tungsto-

phosphate (187), titanium selenite (187), hydra ted stannic oxide

(189), call idinium molybdoarsenate (190), s tannic vanadoarsenate

( 1 9 1 ) , I r o n ( I I I ) a n t i m o n a t e ( 1 9 2 ) , and z i r con ium o x i d e

( 1 9 3 ) . Many s e p a r a t i o n s r e p o r t e d by i o n - e x c h a n g e

p r o c e s s o f t e n i n v o l v e mixed mechanisms i n

25

which sorption effect plays an important part. MItsu

Abe (194) has studied the elutlon behaviour of LI* and

Mg ions with nitric acid solution on crystalline

antimonic acid as a cation exchanger. On the basis of

relevent distribution coefficients for various metal

ions on the resin and crystalline antimonic acid, an

effective separation of Li from large amount of other

metal ions can be performed quantitatively on the

double column which consists of an upper column of

Dowex 50W-X8 and a lower column of crystalline

antimonic acid. Zirconium- titanium phosphate has been

prepared and used for the separation of rare earths and

some other fission products from mineral acids (195,

196). Zirconium arsenophosphate cation exchange column

is used for quantitative separation of uranium from

some metal ions which generally interfere in its

spectrophotometrie determination using sodium

2 + diethyldithiocarbamate as reagent (197). Fe is

separated by cation exchange chromatography on Zr(IV)

arsenophosphate column (198) and application to

synthetic mixtures, capsules or tablets. The complex

forming ability of EDTA at various pH values and the

ion exchange behaviour of Sn(IV) arsenosi1icate and

Sn(IV) arsenophosphate cation exchanger have been

combined in thin-layer chromatography in order to study

26

the separation of metal Ions (199). The distribution of

some metal Ions on Zr(IV) arsenophosphate and Zr(IV)

arsenosi1icate cation exchangers has been studied and

the separation of Al from Mg * in some synthetic

mixtures of antlacid formulations is achieved (200,

201). Another exchangers such as Zr(IV) and Sn(IV)

arsenophosphate are used in column operation for the

analysis of certain alloys and rocks samples (202).

The use of ion-exchange materials not only

restrict to the chromatographic columns for separation

studies but also in fabricating a large number of ion-

selective electrodes in which these materials are

impregnated into polymeric inert matrices which serve

as ion-selective membrane. A variety of weak cation

exchangers have been studied as membrane components for

monovalent ion-selective electrode (203). The

incorporation of zirconium tungstoarsenate into a

polystyrene matrix has been used for zirconyl ion

electrodes (204, 205). Lead ion-selective electrodes

have been developed by using antimonate in an araldite

matrix (206) and cesium selective electrode is

developed using pressed disks of zeolite ion-exchangers

in an epoxy based support (207,208).

A number of inorganic ion-exchangers have been

synthesized in our laboratory and their application

have been extended for the separation studies

(209-212).

27

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201. K.G. Varshney, S. Agarwal, and K. Varshney, Anal. Lett., 16(B9), 685 (1983).

202. K.G. Varshney, S. Agarwal, K. Varshney, A. Premadas, M.S. Rathi, and P.P. Khanna, Talanta, 30, 955 (1983).

203. S.D. Pandey and P. Trlpathi, Electrochim. Acta, 27, 1715 (1982).

204. A.K. Jain, C. Bala, S. Agrawal , and R.P. Singh, Anal. Lett., 15, 995 (1982).

205. S.K. Srivastava, S. Kumar, N. Pal and R. Agrawal, Z. Anal. Chem., 315, 353 (1983).

206. P.S. Thind, H. Singh, and T.K. Bindal , Indian J. Chem., 21, 295 (1982).

207. G. Johansson, L. Faith, and L. Risinger, Hung. Sci. Instrum., 49, 47 (1980).

208. G. Johansson, L. Risinger,^, and L. Faith, Anal. Chim. Acta, 119, 25 (1980).

209. S.Z. Qureshi and N. Rahman, Bull. Soc. Chim. Fr., 959 (1987).

210. S.Z. Qureshi and N. Rahman, Ind. J. Chem., 28A, 349 (1989).

211. S.Z. Qureshi and M.A. Khan, Ph.D. Thesis, Aligarh Muslim University, (1992).

212. S.Z. Qureshi, S.T. Ahmad and N. Rahman, Chem. Anal. (Warsaw) 37, 21 (1992).

C^iPi^P'PE^TWO

Surface Interaction of Ethanolamlne with Hydrous

Zlrconlum(IV) Oxide Gel: Characterization and Separation of Anionic Species

by Column Chromatography

40

There have been continuous Interest in the

synthesis of inorganic ion-exchangers due to their

importance in many areas such as geochemistry,

agriculture, and industry (1-4) etc. Some of acidic salts

of tetravalent metals have a layered structure and

therefore have been studied as inorganic ion exchangers,

since 1964. An exhaustive study such as elucidation of

structure, phase transition catalysis and proton

conductors of zirconium phosphate has been done by

Clearfield (3) and Alberti (5). Recently, ligands have

been intercalated with oc-zirconium phosphate to get a

flexible structure which enhance a selective and

sensitive uptake at micro level of transition metal ions.

A wide range of compounds have been intercalated so far,

for instant intercalation of mono-(6-B-aminoethylamino-6-

deoxy)-B-cydodextrlne. (CDen) has been studied to prepare

a macroporous networks analogous to zeolite between the

layers of Oc-zirconium phosphate by soaking an aqueous

solution of oc-ZrP in varying concentration of CDen at

25°C for 14 days (6). In addition, so many other

compounds like azahetrocyclic compounds, alcohols,

tertiary amines and diamines have been intercalated. The

relationship between the interlayer and the dimension of

the guest molecules is an important factor to uptake the

transition metal ions chelated with ligand [M(ligand)].

The intercalation chemistry of zirconium phosphate has

41

been reviewed r e c e n t l y ( 7 ) . These imply tha t an

i n t e r c a l a t i o n r e a c t i o n may proceed s t o i c h i o m e t r i c a l l y and

be a f fec ted by b a s i c i t y and the s i z e of a guest molecule

or l i gand . I n t e r c a l a t i o n of alkylamines was s tud i ed by

some workers , and the r e l a t i o n s h i p between the chain

length of amine and the i n t e r l a y e r d i s t a n c e of zirconium

phosphate has been d i s c u s s e d . The binding mechanism of

i n t e r c a l a t e d molecules on ion exchangers may be proposed

with e i t h e r of the fol lowing two p o i n t s :

( i ) Formation of hydrogen bond between the guest

molecule and the l aye r s of the ion-exchange .

( i i ) Coordinat ion of the guest molecule which ac t as a

l igand to the c e n t r a l metal ion.

Another class of importance is the functionall7ed oxide

surfaces. These materials are widely studied and used as heteroge­

neous catalyst precursor and immobilization of complexes (8). Nfetal

oxides contain hydroxyl group and/or acid base pair s i tes which

involve coordinatively unsaturated metal and oxygen ions. Thu^

surface func t iona l groups can be in t roduced by

chemisorpt ion or chemical r e a c t i o n of a wide v a r i e t y of

r eagen t s on oxide s u r f a c e . However, ammonia and amines

are most f requen t ly used for the study of acidic-OH

groups of metal oxide ( 9 ) . Also the metal ox ides of high

surface area most f r equen t ly used as ion-exchangers in

d i f f e r e n t pH range in the sepa ra t ion sc ience as well as

42

in catalytic reactions (10-16). The addition of amine

molecule to the zirconium(IV) oxychloride Is carried out

simultaneously by two processes :

(i) to hydrolyse the zirconium(IV) salt,

(ii) to get adsorbed onto the surface of fresh hydrous

zirconium(IV) oxide.

In this chapter we have prepared inorganic ion

exchanger by precipitating zirconium(IV) oxychloride in

the presence of ethanolamine. Amorphous hydrous

zirconium(IV) oxide-ethanolamine gel is obtained by

adding an aqueous solutions of ethanolamine to

zirconium(IV) oxychloride solution. The pH of mother

liquer is adjusted by dropwise addition of a dilute

hydrochloric acid in order to produce a favourable

environment for the hydrolysis. The ethanolamine molecule

is then adsorbed on its surface by weak physical

interaction. The framework the gel produced has been

found to show amphoteric character. This new type of

ion-exchange material is expected to provide a large

number of applications in the separation of cationic and

anionic species.

43

EXPERIMENTAL

ReaRents

Zirconium oxychloride octahydrate (CDH, India),

and ethanolamine (Ranbaxy, India) were used. All other

reagents were of analytical grade.

Apparatus

Spectronic 20 (Bausch S Lomb) spectrophotometer,

systronic digital pH meter for pH measurements. X-ray

diffraction (PXRD) pattern was recorded using a Phillips

APO 1700 instrument, with Ni-filtered Cu-Kscradia t ion. The

IR spectra of the solids were recorded on a Ninnle^ FTTR

spectrometer using kBr disc. FT-IR spectra were recorded

on a Perkin-Elmer FT-IR 1730 spectrometer. Differential

thermal analysis (DTA) and thermogravimetric analysis

(TGA) of the sample were carried out with a Rigaku Denki

thermoflex-type thermal analyzer, model 8076 at a heating

rate of 10°C min~ by using OC -Al^Oo as the reference

material.

Synthesis

All the samples of zirconium(IV) oxide-ethanolamine

(abbrevia ted as ZEA) were prepared by adding aqueous

44

solution of etbanolamine to an aqueous solution of

zirconium oxychloride with constant stirring under

varying conditions, such as pH adjustment, order of

mixing and change of volume ratio of the two (Table 2.1).

The desired pH in each case was adjusted by adding dilute

hydrochloric.acid dropwise. The white gel so obtained was

allowed to stand overnight at room temperature and then

filtered, washed with demeniralized water till the pH of

the filtrate attains a value of 5 or 6, and dried at

40°C. The material broke into small shining particles

when immersed in water.

Ion exchange capacity

The ion-exchange capacity of various samples of

(ZEA) was determined by the column method. A 0.5 g ZEA

exchanger in CI _ form was transferred into the column

(60 X 1 cm) with glass wool support. After that a

1.0 M NaNO as eluant was passed through the column to

elute Cl~ ions, which were determined titrimetrically by

Volhard's method. The results are summarized in

(Table 2.1).

Chemical analysis

The exchanger ZEA-3 (0.5 g) was dissolved in hot

1.0 M hydrochloric acid solution to determine zirconium

45

Ions by chelometric titration (17). To determine the

content of ethanolamine, another (0.5 g) sample of the

exchanger was introduced into a Kjeldahl digestion

flask which contained concentrated hydrochloric and

sulphuric acids and potassium sulphate as catalyst.

After digestion, 25 mL sodium hydroxide solution C50%)

was added dropwise to release amine which was trapped

in 50 mL hydrochloric acid solution (1%). The amount

of ethanolamine released into the solution was

determined titrimetrical ly using a mixed indicator

(Bromo-Cresol Green and Methyl Red) (18).

Chemical stability

The dissolution of various samples of

exchanger were studied in mineral acids, bases and

organic solvents. A 0.2 g of the exchanger (ZEA) in

NO~-form was shaken with 25 mL of the solution/solvent

of interest for 12 hours. The amount of zirconium ion

and ethanolamine released into the solution determined

spectrophotometrically using alizarin red S and

ninhydrin as chromogenic reagents, respectively (17).

The results are summarized in (Table 2.2).

46

pH titration

The pH titration of different samples of

zirconium(IV) oxide-ethanolamine (ZEA) in OH~-form was

performed by Batch method using 0.1 M NaCl-HCl system.

A number of sets of 0.2 g dry exchanger in 0H~ _ form

were placed in different Erlenmeyer flasks. Each flask

is filled with 50 mL of NaCl-HCl solutions in which

0.1 M NaCl is kept constant while the volume of 0.1 M

hydrochloric acid is varied and kept for 24 hours with

intermittent shaking. The pH of the supernatant

solution of each flask was recorded and plotted

against the meq of H added per 0.2 g of dry

exchanger.

Distribution coefficient

For the determination of distribution

coefficient of various anions, 0.2 g (ZEA-3),

exchanger in NO, _ form was treated with 25.0 mL

solution of anionic species of interest in varying

concentration of NH.NOo and in distilled water. The 4 3

mixture was left for 24 hours with intermittent

shaking at room temperature. The amount of anionic

species left in the solution was then determined

spectrophotometrically (19) and titrimetrically (17).

The results are summarized in (Table 2.3).

47

The distribution coefficients of various metal

ions were carried out by treating the exchanger

(ZEA-3) (0.2 g) with 25.0 mL of desired 0.01 M

solution of metal ion using buffering system over a pH

range (3.7-6.0) and in distilled water for each metal

ion. The mixture was allowed to stand for 24 hours and

then filtered off. The metal ion left in the solution

was determined titrimetrically using EDTA method. The

results are summarized in (Table 2.4).

The distribution coefficients (kd values) for

both anions and cations were calculated using the

following equation

Amount of anion/cation in exchanger - . phase per gram 0 -X. » Kd (cm^g ")

Amount of anion/cation in solution 3 phase per cm

Quantitative separation of anions

Quantitative separation of anions were

accomplished on a small glass column (i.d. 0.6 gm)

packed with an exact 2.0 gm exchanger (ZEA-3) in N0~

form. Known volume of anionic mixture was transferred

from the top into the column. It was eluted with

appropriate eluent at a flow rate maintained at 0.5 ml

min throughout the elution process. The results are

reported in (Table 2.5).

48

RESULTS AND DISCUSSION

Various samples of zirconium( IV) oxlde-

ethanolamine are prepared by mixing aqueous solutions

of zirconium oxychloride and ethanolamine under

varying conditions (Table 2.1). It. is observed from

Table 2.1 that the sample ZEA-3 prepared at pH 3

possessed the highest ion exchange capacity and found

stable at 150°C when the studies are made to observe

the effect of variation in temperature. The stability

measurements of zirconium( IV) oxide-ethanolamine in

different concentrations of inorganic and organic

solvents have been summarized in (Table 2.2). The

material (ZEA-3) is found superior over the others and

hence chosen for further studies. The pH titration of

ion_exchange material (ZEA-3) in OH~-form shows a

single point of inflection revealing its monofunc-

tional behaviour. Powder X-ray diffraction pattern

shows the amorphous nature of the material.

The ethanolamine being basic in character

brings about the hydrolysis of zirconium(IV) salt to

produce the hydrous zirconium oxide gel and the

remaining which left in solution get ajjsorbed onto the

surface. The surface of hydrous zirconium oxide gel

contains OH-groups which may occupy the acidic or

basic sites. Generally, the protonated surface species

49

U IX K O O D 2 U. ' -< OOK X >- '^W X i-i 0 ) 2

w u e< < — K

2 Ou 1 U O < •-' X I-. U O W

2 O

< S K O [b

• J U

a

o 2 O X H > t-i < \ S « >

O

2 i o H CO < H K 2 H W 2 2 U O

o o u u

n 0)

1—1

o

u N

CO

• J

1 CO

1 1

•D T3

> > 1—( f—1 O O (0 CO W CO

•i-t 'H •D -D

1 1

T-l rH

^ T-<

'"' '"'

O O r-< CO

o o

o o r-l »H

o o

1 < w

• « * C O

o o

0 +-• •1-1 C x: & CO

o x: a, =

o E <

u

r-l 1

CM CM

r-i T-i

CO ^

o o t-t CO

o o

o o

o o

C M

1

< u

CO 'O'

i H r-l

4-1 • H =

CO

o •C

a =

o E <

CO

u x: CO 1

CO CO

r-i r-(

m TH

O O

o o

o o T-l rH

o o

CO

1

<

CM CD

O O

03 *-> •IH C x: &

CD D O x: a =

o E <

CO

u x:

1 CSJ

TT Tji

CM r-l

rH rH

o o r-l C^

O O

O O

O O

'3 ' 1

< w

r r CD

00 00

o o

1-1 E JC

CO

o

a ~ u o E <

I rH

i n Lo

CO r-l

.rH rH

o o r-< CM

CD O

O O rH rH

O O

I D 1

<

N

CM 00 CO CM

O ' O

0) +-• 1H E x: S CO

o x: a = u o E <

CO

u x: CO 1

o o

rH T-l

r< T H

O O T-i CM

o o

o o r-l rH

o o

cc 1

< w

0)

c • f - l

E

CO x: 4->

©

(0 03

50

(0

e (0

>> (0

c

> 1-1

o

10

(0 p o >

CO

I < N

c •H

a 1-1

o c (0

x:

I 0)

•a X o

E 3

•H c o u u

• H

O

X3 CD

• J 09

N

N

a 1-t

X) CO H

(0 u •H

e m e o

u 0 M + O CO

E

IT) Pi ^ v 00

E

O

en < [I] a: w z

I o z < K H M

J

E to

" 00 E

P M CD < U J

u N

H 2 U > .J o en

o M H !=) _] O cn

o z 05

o o o

1/3

o o

CM r-t O

O CM

o

0 0 - 00 o o

o o o

o o o

o o o

o o o

CS)

o o in

o

00 in rH

O in CO

in 'it

o

o o o

o o o

o o o

o

CO CO O - I Z X

X o CO

z

o CO z

o cn

CM

X

o cn

CM

X

O rH

O c CO

a: o o u X u

o en

P

CO CO CJ) o

51

are formed when b a s i c acceptor such as ammonia,

pyr id ine or amine groups (as probe molecules) i n t e r a c t

with a c i d i c su r face OH-groups, r e s u l t i n g the formation

of NH*, PyH* and -NH* ions r e s p e c t i v e l y . They can

e a s i l y be d e t e c t e d by t h e i r c h a r a c t e r i s t i c v i b r a t i o n a l

modes in the IR r e g i o n s . Thus, the ammonium ion NH.

4

gives rise to the normal N-H stretching modes near

-1 + 3230 and 3195 cm and to asymmetric NH deformation

mode at about 1430 cm~ . The pyridinium ion PyH*

absorbs at about 1485-1500, 1540, 1620 and 1640 cm"'*".

These sets of vibrational modes permit an unequivocal

distinction between the protonated molecule and simply

H-bonded or coordinatively adsorbed species. In

certain, cases, however, a continuous absorption band

over the whole spectral range may be observed (20).

This had been explained by the formation of highly

polarizable H-bonds which are probably produced in

dimeric species of the type H^N.^.H ...NH_ and

Py...H ...Py. The acidic surface on amorphous silica

and alumina gels, for example, have also been detected

by their characteristic vibrational modes. The basic

character of OH-group may be arised due to unsaturated

lattice ions; oxygen ions as Lewis base and metal ions

(which is Coordinatively bonded) as Lewis acid. The -2

nucleophilic character of 0 ions results in dehydroxylation of oxide surface (condensation of OH

52

groups and subsequent elimination of \water). Thus,

giving rise to the frequency modes near about 1020-975

and 860-800 cm for dehydroxylation at temperature

range between 300-970 K. The detection of basic

character is rather difficult as the suitably probe

molecules are not frequent as in the case of acidic

active sites.

A comparative study of IR spectra of hydrous

zirconium{IV) oxide gel (spectrum A), pure ethanol-

amine (spectrum B) (Figure 2.1) and zirconium(IV)

oxide-ethanolamine (sorption of ethanolamine on the

surface of zirconium(IV) oxide; (spectrum C) (Figure

2.2) reveals the following findings :

Spectrum A : A broad band lying in the frequency

region 3500-3100 cm" is attributed to the lattice

water molecules, free surface hydroxyl groups and a

diffuse band (1600-1500 cm' ) to the water of

crystallization.

Spectrum B : A broad band lying in the region

3500-2400 cm" which on resolution gives two bands at

3330 and 2850 cm' due to N-H and C-H stretching

respectively. (This covers the OH stretching

frequencies of alcoholic group, 3600-3200 cm ).

53

aoueiJTuisuBJX

54

Another strong bands at 1590 and 1350 cm" are

attributed to N-H deformation and C-N stretching

respectively. The C-0 stretching and 0-H deformation

(coupled) have been observed at. frequencies 1160 and

1070 cm respectively, from alcoholic hydroxyl group.

Spectrum C : A broad and continuous absorption band in

the region ranging from 3600 to 2100 cm , (which

contains the bands of spectrum A fi B lie within this

range) may be reasonably ascribed to the sorption of

ethanolamine at the surface of hydrous zirconium(IV)

oxide gel. The -NH* ion give rise to the normal N-H

stretching mode near 3230 and 3195 cm which are

difficult to Identify due to the continuous

absorption. The formation of -NH* ion results from

H-bonding interactions occur between basic acceptor

molecule (ethanolamine) and acidic surface OH group of

zirconium(IV) oxide, thereby showing the presence of

protonated surface species which is further confi'rmed

by a sharp band at 1440 cm" due to asymmetry -NH^

deformation mode. The two bands at 2900 and 2864 cm

suggest the CH stretching. The broad width absorption

extending to below 1600 cm , is attributed to

perturbation possibly due to strong adsorption of

ethanolamine on the surface of the gel (21). Band at

55

e o

i _JO CM

in o in

00 u> CM 00 -J-m O O

PO

N

C i - (

E CO rH O c to

0)

X o

3

8 in CM

O O O n

O O in

O

(4 0)

e 3

c 05 &

C o o .H 3

o

+3 cj U ^ e

OS o

H CD tti ^

CM

•

00

[b

8DUeUTHISUEJl

56

1625 cm is ascribed to the deformation of water

molecules (details are discussed in Spectrum A). This

band shifted to 1050 cm on adsorption of -NH„. The

shifting in wave number is. explained by Zr-0

interaction with -NH group resulting the formation of

H-bonding.

The thermal methods which include TGA 8 DTA

analysis of the ion-exchange material (ZEA-3) are

shown in(Figure 2.3).The initial drop in weight below

350°C is attributed to excess water as Indicated by

TGA. The endothermic peak at 80°C on the DTA curve

shows the loss due to surface adsorbed water. The TGA

curve shows that the sample is stable upto 350''C after

which dehydroxylat ion of OH group takes place

resulting the dissociation of ethanolamine (exothermic

peak at 443°C on the DTA curve). Another endothermic

peak at 539*0 on DTA curve indicates the removal of

interstitial water. After 550°C the exchange material

is stable.

On the basis of chemical composition, TGA, DTA

and IR analyses the ratio of zirconium(IV) oxide :

ethanolamine is 1:1 and the empirical composition of

the material is

[ Zr02(OHCH2CH2NH2) .X H2O 1^ , x = 1

57

u

0)

3

03

s

W N

CO •H

CO

e

{%) m8T9M

58

The number of water molecules per mole of exchanger

was calculated using the Alberti's equation (5),

18x = W(m+18x)/100

where x is the number of water molecules, w is the %

weight loss of water and m is the molecular weight of

anhydrous material. The structure and mechanism a're

shown in (Figure 2.4).

The distribution coefficients (Kd values) of

different anionic species are studied in distilled

water (DW) and in different concentrations of ammonium

nitrate. The results are summarized in (Table 2,3). A

look at the table suggests that ammonium nitrate

contribute a significant role in decreasing the Kd

values in which there might be a competition between

the nitrate and the anion under investigation to

occupy the ion exchanger sites. The affinity series

for halide ions is Cl~ > Br~ > I~ in water as well as

in different concentrations of ammonium nitrate,

suggesting the basis of their ionic radii which

follows the same order. The Kd values of Cl~, Br~ and

OH II

Zr . y Zr;

OH

. Z r -"O

Surface

+ HOCH2CH2NH2

1 Interaction

HO ^CH7

^= 0/ 1 Ho^ H,0

Protone shift

H O • ^CHj

HjC ^ ^,

H^( !

HjO

- H j O I -(HOCH2CH2NH2)

ZrOj

59

Figure 2.4 Structure and the mechanism of synthesis .

CO

O Z X z

u c o u 00

c

•H

CO

> •D c (0

Q

c

CO I

< N

C o CO

c o •H

c CO

<D E o CO

C 0)

CO •

Cvj

o t-*

G (0 H

0) o CJ c o 1-4 4->

3 X3 •rl

u 4->

CO •H O

CO O Z '^

a: z O Z o < H Z m o z o o

o CO

o

o CSl

o t-l

o

CVJ

z o M z <

o z en

60

CD

in

CM

i n CNJ

in CO CM

CO CO

in t CT)

in CM

o

in CSl CO

CO in CO CM

in CM CO

CM CO

- in

CO in in

in

in

c CO

CO

o ^ o CO CM

o o o

in c^ C7)

CM

00

CO iH t C>3

in

c 00 TH

t 00 in

o o . in

CO CM

r-l ^ C

00 CD >

o in CO

c in

in CM Q

O CO C3)

in t^ CD

rH 00

CM

O in

o CSl

o in CO

CM r-t in

CO in in in

TH

•<* O

TH 00

c

in CO • ^

CO LO

CM CO

o

o o o r-l

C^ 00

o

CM t-l 00 CM

O in C J CM

o o r

TH CO in

o o in CM T-l

t CO 05

in Cvl CD

CO I>

in CSl

in CM

in CM

o O in CM

O o CO CM

in CM CO

in [ in

1-4

u

1 u m

1 i-i

" r.

o CM o

1 CO

o >

U CO

O U ' <D O f- cn

O li "^ M ^a- ii CO cvi O O O

1-. c o ra U S S W

CM in CO 0 0 o i

61

l" are found low In comparison with other anionic

species such as MnO., V0~, Cr-O" TeO-, SOj. On the

basis of the Kd values, some binary separations have

been achieved (Table 2.5).

Distribution coefficients of various metal

ions are studied in distilled water and in aqueous

conjugate acid-base buffer systems to form a buffer

zone of different pH ranging from 3.72 to 6.00. The Kd

values of different metal ions have been summarized in

(Table 2.4). The small Kd values, found with almost

all of the metal ions, suggest that the cationic

behaviour of ion-exchange material is very poor.

Further, the complexation of metal ions with amine

group also poor due to non-availability of these

groups which might have been strongly adsorbed on the

surface of the zirconium(IV) oxide.

62

00 c a u

X

c CO u

a

•D C CO

u 0)

a

•o 0)

CO • H

•a

c • H

CO

c o

CO

0)

B C M

o

(0

c 0)

T}l

• N

(D l-H

X3 (D H

0) O u

c o

• H 4-> 3 £) • H ^4 4-< CO

• H Q

« /~ o o

• CO 1

eg t -•

CO

^'

X

a

o o CO

o o in

o o

CO

Q M • J >J M K H ta en H HI < Q S

< en

W O

O

C/3

O) CD CM r^

ro CM

CO T-l

CO C J 1

I D CSJ

in CM 1

•'t o

00 00

CO

o CO

o CO r-<

o CM

CO 1 CS

CD CM

CO

•, CO

o

CO

• CO

o

o •

I > T-l

00

• CO 1 r-l

CO

• CO r-f

CD 00 • •

l O CO O rH

CO CO

CO O CM CM

O CT> 0 0 CM O

O CO CO C^

0 0 C75 CO l O CD CO

in CNJ

CO O • ^ CM r-l • ^

CM CO t ^ in O O

+ + + + + + + + + + + C O C M C O C S J C ^ C M C g C M C M C M C M

t i C C D O ' > - < 3 C ' D 0 0 C 0 0 0

CM CO in CO CO Oi

X

a •D m u •H (0 03 •D 0)

•D 0) +j

CO p

• • — I •D CO

O Pu DC CM

CO Z

o

c o

o

CO

CM

•D

•n o

•4->

CO • H CO

c o u

CO

>> m

u 0

CtH <tH

0) £ H

u CD

O • iH

( j

•»-> f H

u C M

O

c o

•1-t

•*-• D f—I

n en 2

o i H

• O

63

Table 2.5

Separation of anions achieved on Zr(IV) oxlde-ethanolamine

exchanger. (Sample ZEA-3).

S.NO.

1 .

2 .

3 .

4 .

5 .

6 .

ANIONS

cT MnO"

4

B r '

MnO 7 4

I "

MnO 7 4

C l '

sof 4

B r "

sof 4

I"

SO* 4

AMOUNT LOADED (mg)

0 3 . 5 8

0 1 . 9 5

0 7 . 9 8

0 4 . 9 8

0 2 . 6 5

0 9 . 6 2

0 3 . 6 0

0 2 . 5 5

0 7 . 6 5

0 5 . 2 1

0 2 . 6 5

0 9 . 5 2

% RECOVERY

1 0 0 . 0 8

9 5 . 7 0

1 0 0 . 5 5

9 8 . 0 3

9 8 . 9 0

9 9 . 2 0

1 0 1 . 0 5

9 6 . 5 0

9 9 . 8 5

9 8 . 9 9

1 0 0 . 0 3

9 5 . 8 0

VOLUME OF EFFLUENT (mL)

60

70

40

80

40

80

40

60

40

60

40

60

ELUENT USED

"2° 0 5 . M NH^NOg

H^O

0 . 5 M NH^NOg

"2° 0 . 5 M NH^NOg

"2° 0 . 5 M NH.NOo 4 3

"2° 0 . 5 M NH^NOg

"2° 0 . 5 M NH.NOo 4 3

64

REFERENCES

1. C.B. Amphlett : "Inorganic Ion Exchanger", Elsevier Publishing Company, New York (1964).

2. V. Vesely and V. Pellarek, Talanta, 19, 219 (1972).

3. A. Clearfield, Chem. Rev., 88, 127 (1988).

4. M. Abe, T. kataoka and T. Suzuki : "New Develop­ments in Ion Exchange ICIE'91", Tokyo, Japan, October 2-4 (1991).

5. G. Alberti, E. Torracca and A. Conte, J. Inorg. Nucl. Chem., 28, 607 (1966).

6. T. Kljima and Y. Matsui, Nature, 332, 533 (1986) .

7. Y. Hasegawa and I. Tomita, Trends in Inorg. Chem., 2, 171 (1991).

8. L.L. Murrell : "Immobilization of Transition Metals; Complex Catalyst on Inorganic Supports In Advanced Materials in Catalysis", J.J. Burton, R.L. Garten (Eds.). New York, San Francisco, London : Academic Press, 235-265 (1977).

9. J.R. Anderson and M. Boudart : "Catalysis", Springer Verlag, Berlin Heidelberg, New York, 4, 71 (1983).

10. K.M. Pant, J. Indian Chem. S o c , 46, 6541 (1969).

11. J.D. Donaldson and M.J. Fuller, J. Inorg. Nucl. Chem., 32, 1703 (1970).

12. (a) A.J. Ruvarac and M.I. Trtanj, J. Inorg. Nucl. Chem., 34, 3893 (1972).

(b) E. Hallaba, N.Z. Misak and H.N. Salama, Indian J. Chem., 11, 580 (1973).

65

13. H. Yaroaaki, M. Kaneda and Y. Inoue, Bull. Chem. Soc. Jpn., 63, 3216 (1990).

14. M. Sugita, M. Tsuji and M. Abe, Bull. Chem. Soc. Jpn., 63, 559 (1990).

15. X. Liu, K. Lu and K. Thomas, J. Chem. S o c , Faraday Trans., 89, 11, 1865 (1993).

16. S.Z. Qureshi and G. Aslf, Ph .D. . Thesis, Ali'garh Muslim University (1995).

17. F.J. VVelcher : "The Analytical Uses of EDTA", D. Van. Nostrand Company, Inc. Princeton, New Jersey, 188-189 (1958).

18. J.J. Mitchell, I.M. Kolthoff, E.S. Proskaner and A. Weisberger : "Organic Analysis", Interscience, New York, 3, 140 (1956) .

19. F.D. Snell and C.T. Snell : "Colorimetrlc Methods of Analysis", D. Van Nostrand Company, Princeton, New York, 2, (1957) .

20. H. Knozinger : "Hydrogen Bonds in Systems of Adsorbed Molecules. In : The Hydrogen Bond". P. Schuster, G. Zundel, C. Sandorty, (Eds.). Amsterdam, New York, Oxford : North-Holland Publ. Comp., 3, 1263-1364 (1976).

21. Ref. (9), pp. 78.

C^HSM!£1!^%, 't9&^'L

Thin-Layer Chromatographic Behaviour of Carbamate Pesticides and

Related Compounds on Zirconium Phosphate Layers.

66

Thin-layer chromatography (TLC) of pesticidal

compounds have attracted the attention of scientists

for several years. Even recently TLC is widely applied

as a simple quantitative method for the analysis of

pesticides (1). Moreover, environmental pollution have

become common events due to the indiscriminate use of

various types of pesticides. These compounds are known

to display various types of acute toxicity (2) and as a

result the availability of safe drinking water and food

products have become a matter of special concern (3). A

screening programme of the systematic forensic and

toxicological analysis of 170 pesticides has been

carried out which is based on TLC detection in

combination with GC and UV spectroscopy (4). Wi th the

availability of many other methods such as gas

chromatography, high performance liquid chromatography,

supercritical fluid chromatography, spectrometry,

enzyme Immunoassay, and capillary electrophoresis (5),

the TLC and high performance thin-layer chromatography

(HPTLC) have proved to be a valuable tools providing

accurate and precise quantitative analysis of pesticide

residues ranging from ppm to ppb concentration levels.

The recoveries of pesticides range from 82-112% for a

concentration limit of 0.5-5.00 ppm. For instance,

67

N-methylcarbamate insecticides are extracted from water

using C. p (HPTLC) plates with solid phase extraction

method (SPE) followed by TLC on HP preadsorbent silica

gel plates developed with toluene-acetone (4:1). For

the development of carbaryl, carbofuran, and

methiocarb, the solvent system hexane-acetone (75:15:

10) is used, and the spots are detected with

p-nitrobenzenediazonium tetrafluoroborate as spraying

reagent (5). In another study, carbaryl is separated

from related compounds such as phenol, o-nitrophenol,

oc-naphthol, and carbofuran on silica gel G plates (7).

Carbaryl in water is also determined by TLC on silica

gel G plates after its extraction with chloroform (8).

Pandalikar et al. (9) have developed a plain thin-layer

chromatographic (p-TLC) procedure for the detection of

carbaryl at trace levels in biological fluids. Another

(P-TLC) scheme is developed (10) for the separation of

carbaryl, bendiocarb, carbofuran,baygon, ziram, zineb,

aldicarb, 2-isopropylphenyl-N-methylcarbamate (MIPC),

and 2-sec-butyl-N-methylcarbamate (BPMC) on plates

coated with silica gel containing 1% zinc acetate.

A survey of the literature reveals that most

pesticides identification and determinations have been

performed on silica gel TLC and HPTLC plates. In the

68

recent past attention has been focussed towards

stationary phases with different characteristic

properties to be interacted more strongly to get

improved resolution. For instance, silica particles

have been modified by introducing amino-, cyano-, or

diol-bonded groups to interact in a different manner

(11). On the other hand some new techniques have

emerged recently based on the use of molecularly

imprinted polymers (MIPs) (12). One of the interesting

techniques is microchannel thin-layer chromatography

where zirconia is used as stationary phase (13).

Recently, the behaviour of some carbamate pesticides

has been examined on TLC plates coated with alumina,

barium sulphate, calcium sulphate, cellulose and silica

gel G (14). Nowadays, the use of inorganic ion-

exchangers as coating material in TLC plates has found

a place to achieve important separations (15).

In this chapter we, therefore, choose zirconium

phosphate ion-exchanger as coating material for

thin-layer chromatography of carbamate pesticides and

related compounds.

69

EXPERIMENTAL

Apparatus

A stahl apparatus with applicator, glass plates

(12x4 cm), glass jars (15x5 cm), a temperature

controlled electric oven (Technico), and an electrical

hot-plate with magnetic stirrer (Remi 2LH) were used.

Reagents and Chemicals

Compounds were of laboratory-reagent (LR),

general-reagent (GR), wettable powder (WP) or analyticl

reagen (AR) grade. Silica gel G (Merck), carbaryl (WP)

(Paushak), darbofuran (GR) (Pesticides), mancozeb (WP)

(UPL), carbendazim (WP) (Northern Miner.), phenol (LR)

(BDH), p-chlorophenol (LR), (BDH), o-nitrophenol (LR)

(CDH), OC -and p-naphthol (AR) (CDH), zirconium

oxychloride octahydrate (LR) (CDH) were used. All other

reagents were of analytical-reagent grade.

Preparation of solutions

Solutions (1%) (W/V) of carbaryl, carbendazim,

carbofuran, mancozeb, phenol, p-chlorophenol,

70

o-nitrophenol, oC -and p-napbthol were prepared in

acetone. The test solutions were applied with a

microsyringe or fine capillary to the plates. 1 ml

saturated silver nitrate was added with stirring to 20

ml acetone and the mixture treated dropwise with water

until the precipitated AgNO- had just redissolved. It

was then used as a spray reagent for the detection of

pesticides.

Preparation of TLC plates

A solution of zirconium oxychloride (0.1 M,

prepared in 0.1 M HCl solution) was added to a 0.2 M

disodium hydrogen phosphate in the ratio of 1:1 to get

zirconium phosphate gel which settled down after 30

minutes. The mother liquor was decanted and the gel was

washed with deionized water. It was mixed thoroughly

with 0.25 M calcium sulphate to obtain a homogeneous

slurry. Calcium sulphate was added as binder which was

found strong enough not to allow the coating to form

cracks as it dried due to shrinking of ZrP gel.

Furthermore, the binder interaction with the sample

molecule was to be as low as possible in order to avoid

undesired interference on the plates. Thus, a ratio of

binder to ZrP of 1:2 (W/W) was chosen. The slurries

71

were applied to the glass plates (12x4 cm) with the

help of applicator. The layer thickness after drying

was estimated to be 0.5 mm. The plates were first

allowed to dry at room temperature (25 + 2''C) and then in

an oven at 100°C for one hour. The plates could be

stored at room temperature for several weeks with

unchange chromatographic properties. The manufacturing

of the plates was readily reproducible as demonstrated

by the chromatographic data obtained.

72

RESULTS AND DISCUSSION

The relative merits of using silica gel and

zirconium phosphate plates to the identification of

carbamate pesticides and related compounds in the same

solvent systems have been summarized in (Table 3.1 and

3.2). A comparison of R. values of (Table 3.1 and 3.2)

shows that most of the pesticides are retained more

strongly on zirconium phosphate than silica gel plates.

This may be attributed to the presence of more active

sites with hydroxyl groups on the ZrP surface and/or

acid-/base pair sites which involve coordinatively

unsaturated surface metal and oxygen ions, resulting in

multiple types of physical interaction other than

adsorption, ion-exchange partition, and any

combination of the two taking place on silica gel

plates. The results shown in (Table 3.1) will be

discussed more precisely taking into account the role

of polarity of different solvents and their ratios of

mixing with each other. The pesticide compounds are

divided in two categories in accordance to the R.

values in different solvent systems :

Category A : OC-Naphthol, p-naphthol, 4-chlorophenol,

0-nitrophenol, and phenol. Which show larger movement.

73

Category B : Carbaryl, mancozeb, carbendazim, and

carbofuran. Which show smaller movement.

On reviewing the R. values in different solvent

systems, one finds a systematic increase/decrease in

R- or a complete retention of the compound at the point

of application (that is R. = 0.00). The group I

comprises the solvent systems S , S„ and So. In the

solvent system (S^), the R„ values of both categories

(A S B) show almost zero movement (except a few ones

which move slightly) and this effect may be regarded to

a small polarity of cyclohexane. Now adding the

solvents of increasing polarity e.g., ether < acetone

to cyclohexane (S 8 S„), the category A compounds show

better movement with compact spots than category B

compounds. In group II (S 8 S^), the S^ which is a

pure chloroform, the movement of category A compounds

is moderate, however, the category B compounds are

still retained. On increasing polarity by adding

acetone, there is a substantial increase in R in both

the categories (A 8 B) compounds. The same effect has

also been found in groups III-IX solvent systems. On

reviewing the R , values, one finds that carbofuran is

retained completely (R = 0.00) in almost all the

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78

Table 3.2

R, values of carbamates and related compounds on sil ica gel G plates .

'to

a:

t-H n o S

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0.45

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1.00

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0.80

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0.88

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0.72

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< CO

<

0.27

0.00

0.76

0.42

0.50

0.80

0.64

0.45

0.60

0.98

0.96

0.95

0.76

CQ U N O U z <

0.86

0.88

0.95

0.90

0.86

0.85

0.85

0.76

0.72

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1.00

0.95

0.85

*-* N < P Z u 03

<

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0.00

0.60

0.42

0.95

0.69

0.45

0.45

0.65

1.00

0.96

0.95

0.80

z <

O 03

<

0.56

0.00

0.57

0.52

0.25

0.45

0.36

0.00

0.29

0.85

0.96

0.86

0.65

Table 3.2 continued

79

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15

16

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19

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1.00

0.95

0.05

0.73

0.95

0.80

0.98

0.98

.J O X H X

< 2 ti

1.00

0.93

0.05

0.66

1.00

0.66

1.00

0.95

o 7. X IX

o o •J

X 1

0.95

0.86

0.05

0.66

0.91

0.68

0.95

0.90

HJ

o z a: O

6

0.88

0.93

0.27

0.63

0.80

0.30

T 1.00

0.90*

o z

0-

1.00

1.00

0.00

0.80

0.76

0.66

0.90

0.90

< DQ

<

1.00

0.94

0.00

0.76

0.76

0.72

0.60

0.86

m N o u z <

0.92

0.94

0.76

0.80

0.90

0.76

0.75

0.70

< P Z w PQ

<

0.92

1.00

0.36

0.82

0.90

0.63

0.70

0.80

z < OS

b O (Q 02 <

0.85

0.60

0.00

0.54

0.90

0.45

0.70

0.60

a) The composition of the mobile phases is specified in Table 3.1

T) Tailing spot .

eo

CO

B CB

rH

a o H o

a

B 0 0

c CD O U

(0 cs

0) 0 0

B a x: a (0 o x: a B P

• H c o u ( i

<rt N

c o CO

c

l-H

o

as

.J o CO

(0

o

Q

H < < »

cn

o N t^ *

(—1 > v ^

1—1 O x: •t-i

x: a m n 1

CO.

• o *—' l -H

o c 0) x: a

'U c eo

^ «3 O

O x: +- •

x: a (0 c I

o

o c 0) x: a o u o »—I

x: o

i n

CD CO

o 4-' x: a CD

c

CO

o

N CO

•D C 0 o

(B X)

• is a " o

o CJ5

o x: 4-> x: a CD

c I

CO

o c x: a o u

*-> • H c I o

•D c CD

N t^

>> U CO X) u CO

o

<D CO

CO

CD XI u CD O

CD CD

O

X3 CD N O O

c CD

e

CO

o c 0) x: a o *->

c I o

cc CD

C D CO

X3 0 N O O C CD

O LO

O c 0) x: a o • H c I o

CO to

•a c CO

CO

o sz 4-> x: a CD c I

8 ^ / ™ ^

lO CO

• o '"' l - H

o c CD JZ a o u o

l-H

o "'t

(T> CD

o

r H

o c (D x: a

c CD

B

•» o ** •

o t t a ^

E •rH N CO •D C

CD O

O

c Q) r a

^ LO •<3<

• O " " " • ^

r—1 > l t j

CO X3 U CO

U

^ r-^

o 00

• o ^^ f - H

o c 03 x: a o u o

l-H x: o 1 "<*

00

* o

o XT. +-• x: a CO c OJ.

CO CD

X3 <P N O O C CO

E

00

o

JH CO

XJ

CD

O

00

o c 0) x: a o <H

•iH c I o

CM In i> to

• • o o o

c 0) x: a

tn

N CO

c

•a c CD

O C •*-'

x: a CO

c

i n

o c CD x: a o u o

^ :s CD O

O CO

o x: x: a CO

c I

CO.

c U

.03

0 0

c (0

.s x: u CD

o IX S o u

o o

c CD u 3

«tH

L I CO O

O CO

C CO

u o

(4H

CO

u

c CO

-—. o O PN)

. o

c (0 ( H

3 <tH

5 J H CD

u

N CD

c 0

u CD U

o

c CO

3 «i-i

CO

o o

c CO

u 3

(4H

CD

u

CO

x» CO

C Q

CO * J CD U CD

a

o z 05

81

•a 0) D C

• i - t

*-> C o u

CO

• CO

0) rt JD a ^

• J o U)

2 O

b

D U H <

< cu tc (/)

s 2 • 3

O

o o

d z • CO

1

(C CO

o

N O O

c

d 1—( o

a 03

c 1 P3-

•• CO m

• o

1—(

o x: +-" sz a CD

c 1

8

o CO

o

1—I

>> ^ 1

03 X) L I

a

l - H

>

o o d c m u

5 U m u

"D c 03

O CQ

d E

•r- l N CO •D C

B u 0) u

o cs

CD

•D C 03

O LO

o

E N CO

C

£>

CD O

^ O

O CD —' •

o C - - ' 03

5 5 u u 03 01 U O

,_< o

^ d 00 ""'

^ c ,:H 03 o x: c a 0) O

U i • H

P f= J:? ' 5 o

^ CO

M l -H

>

t^ rH

CD

CO

• o

l-H >> u 03

J3 U OJ U

CD

• O

f-H

o

x: a m c OQ.

^ ^ ' O

rH CO o o ^^

« E C 1 "D

a c 03

,_>

• o

l-H o c 0

^ x: o o. o o • u ci -H

c l-H 1

o o c x: c (X 03

hH l-H l -H

>

00 en

o •

o

l-H o c 03 x: a o u

•t-i • H

o

CO CD

d l - H

o c 0

x: a

? *

o

l-H >> Ll

m X) ( 03 O

O CO

d X5 (U N o o c 0!

X l - H

o CO

d »—' l-H

o c 03 x: a o u o

f - i

x: u 1

T3

c 03

CO rH

cn

^ - N

* c

2. « I - " ' " ^

c w 0 d a ° g 4-1 - i - l

• i - i N C 03 1 -D o c

0) - X)

•"' u :^ 03 kb o o

o to

S £ x: ^ a ^ S >>

1 ^ T t O

in •

r" o CO

o o '"' x:

*-•

4-> CD

x: c Q- 4, 03 « -

2 1 "O

» s

X

rH

d

c 03 U . 3

<(H

5 L> 03 U

• CO 0) en 03 x: H-J c 0) L> 03

a c

• H

c 03

5 • H oo 03

03

CO 03

l-H

03

>

«-a:

a

81

1

0.8

0.6

0.4

0.2 -

Mancozeb Carbofuran

1

0.8 \

0.6

0.4

0.2

0-Nitro phenol Phenol Carbary l

P-Naphthpl

10 20 30-70 80 10 20 30-70 80

Solvent Polari ty E!!!,(30) X 100

10 20 30-70 80

Figure 3.1 Solvent polar i ty and R, values of carbamate pesticides and re la ted compounds on zirconium phosphate l a y e r s .

83

different types of the solvent systems and therefore,

it is possible to separate it from its own compounds as

well as from the compounds of category A.

The hydroxyl groups on ZrP surface may undergo

condensation with elimination of water resulting the

dehydroxylation of oxide surface. The dissociative

OH OH 0

Zr + Zr >• Zr Zr + H O

chemisorpt ion has been observed with dehydroxyla ted

oxide surface with many organic as well as inorganic

molecules. For example N-H bond rupture has been

observed for CH-NH^ and (CH )2NH according to (16).

I 0 N OH

/ \ I I M M + (CH )_NH ». M + M

In the above reaction, not only the chemi sorpt i on of

the compound on the surface result, but also there is

the reproduction of surface 0-H group. The compounds

carbaryl and carbofuran which also contain the N-H

84

bond may undergo dissociation resulting the

chemlsorption and hence showing smaller movement from

the point of application. In case of carbofuran, the

N-H group is attached with bulky groups than other

compounds of category B and hence attributed to a small

R., almost to zero in most of the solvent systems.

65

REFERENCES

1. S. Sherma, J. Planar Chromatogr., 7, 265 (1994).

2. S. Safe, CRC Crit Rev., Toxicol, 13, 319 (1984).

3. K. Seshaiah and P. Mowli,. Analyst, 112,: 1189 (1987).

4. F. Erdmann, H. Schuetz, C. Brose, and G. Rochholz, Beitr. Gerichtl. Med., 49, 121 (1991).

5. T. Cairns and J. Sherma, Modern Methods for Pesticides Analysis: Emerging Strategies for Pesticide Analysis, CRC Press, Boca Raton, FL, USA (1992) p. 352.

6. S.C. McGinnis and J. Sherma, J. Liq. Chromatogr., 17, 151 (1994).

7. H.S. Rathore and R. Sharma, J. Liq. Chromatogr., 15, 1703 (1992).

8. H.S. Rathore, H.A. Khan, and R. Sharma, J. Planar Chromatogr., 4, 494 (1991).

9. S.V. Pandalikar, S.S. Shinde and B.M. Shinde, Analyst, 113, 1747 (1988).

10. S.P. Srivastava and J. Reena, J. Liq. Chromatogr., 6, 139 (1983).

11. J. Sherma, Anal. Chem., 64, 134R (1992).

12. Kriz, C.B. Kriz, L.I. Anderson, and K. Mosbach, Anal. Chem., 66, 2636 (1994).

13. S.P. Bouffard, J.E. Katon, A.J. Sommer, and N.D. Danielson, Anal. Chem., 66, 1937 (1994).

14. H.S. Rathore and T. Begum, J. Chromatogr., 643, 321 (1993).

15. S.A. Nabi, W.U. Farooqui, and N. Rahman, Chromato-graphia, 20, 109 (1985).

16. B.A. Morrow and I.A. Cody, J. Phys. Chem., 80, 1998 (1976).

Preparation and Characterization of Layered Double Hydroxides and

Intercalation Behaviour of Sulfamic Acid And Dodecylamine

86

Increasing interest Is being paid to the

layered double hydroxides. This interest stems from

their possible role as important intermediates in

natural mineral transformation and geochemical

processes, and also from their technical applications

as adsorbents, anion exchangers, catalysts and

molecular sieves (1-8). Layered double hydroxides or

mixed-metal hydroxides family (LDHs) have been

structurally characterised in which some divalent metal

cations have been substituted by trivalent ions to form

positively charged sheets balanced by interlayer

cabonate anions (9). LDHs have the general formula

[• '[i-x) ^'''^^^h^ (A"-)^.nH20

where M represents divalent metal cations where as

M represents trivalent metal ions and A is the

gallery anion to balance the net positive charge on the

double-metal hydroxides. The preparation, properties

and applications of these salts have been reviewed

- - 2 +

recently (10). The anion such as CI , OH and CO- are

cited as the charged balancing anions although various

attempts have aimed at increasing the interlayer

distance by incorporating large anions in the gallery.

Thus, the intercalation of Iso- and heteropolyanions

87

such as [Uo^O^^]^~, [V^QO^g]^'. [ cc -SiW^iOgg]^".

[a-.H2Wi| 2°40 '' ^"^ f^^^3^9°40-'^~ ^^® ^^®" carried out

(11-13). The interest on me taJate-exchanged layered

double hydroxides originates from their potential

application to adsorption and catalysis. In fact,

layered double hydroxides intercalated with [Mo„o„.]

and [V.„0„„] ' anions are tested as catalysts for the 10 Z o

decomposition of 2-propanol and dehydrogenation of

p-butylethylbenzene (14). The direct synthesis of

materials with anions other, than carbonate is quite

cumbersome and limited, requiring the total exclusion

of carbon dioxide at each stage (1,15). However, if the

replacement of carbonate after synthesis is done, the

process becomes easier (16). Recently, certain organic

species have been incorporated by the exposure of

heat-treated layered double hydroxides to the solution

under study (17).

In this chapter, we describe the preparation of

layered double hydroxides of Mg(II) Al(III) and

intercalation of dodecylamine and sulfamic acid into

the heat-treated sample.

88

EXPERIMENTAL

Reagents and techniques :

All starting materials were from Merck

(standard laboratory grade). Elico LI-IOT pH meter was

used for pH measurements. Remi 2LH magnetic stirrer.

Powder X-ray diffraction (PXRD) pattern was recorded

using a Phillips APO 1700 instrument, with Ni-filtered

Cu-Koc radiation. The FT-IR spectra of the material was

recorded on, a Perkin-Elmer FT-IR 1730 spectrometer.

Differential thermal analysis (DTA) and thermogravi-

metry (TG) of the sample were carried out with a Rlgaku

Denki thermoflex-type thermal analyzer, model 8076 at a

heating rate of 10°C min by using oc-Al_0» as the

reference material.

Synthesis of the layered double hydroxides of Mg(II)

AKIIIj-COg^-

The parent LDH was synthesized by the method

established by Reichle (1). A Mg/Al ratio close to 2

was chosen since this was known from other studies to

give samples of good crystal 1inity. A solution

containing 0.1 mol (0.5 M solution) of Mg(NO )2.6H20

89

and 0.05 mol (2.5 M solution) of A1(N0^3.9H20 In 70 ml

of delonized water was added with vigorous stirring to

a solution of 0.35 mol (0.5 M solution) of NaOH and

0.09 mol (4 M solution) of Na CO- (anhydrous) in 100 ml

of delonized water. The addition was over a period of 1

hour at room temperature at a pH maintained close to

10. The resulting slurry was then crystallized at 65°C

for 18 hours followed by cooling and washing several

times with delonized water.

Synthesis of the host material was carried out

by calcination the Mg(II) Al(III)-carbonate in air at

450+10°C for 6 hours. One gram of the calcined material

was then added to a 100 ml" of 0.10 M aqueous solution

of sulfamic acid in one case, and a 0.10 M alcoholic

solution of dodecylamine in the other. The two mixtures

were kept on stirring for 3 days at room temperature.

The products were then separated by filtration and

washed with hot distilled water. Once Incorporated the

amine-LDH appears stable.

Sorption capacity

The sorption capacities of various metal ions

were carried out. Two grams of the intercalated-LDH

90

material were kept in a 100 ml of 0.01 M hydrochloric

acid over night. After washing with distilled water 0.2

gm of the material was treated with 25.0 ml of 0.01 M

solution of metal ions. The mixture was left for 12

hours, with intermittent shaking, at room temperature.

The amount of metal ion left was determined

t i trimetrlcally.

pH-titration

The pH-titration was carried out by batch

method. A set of 0.2 gm of material in H -form with

0.10 M NaOH and 2.0x10"^ M Cu "*" solutions were

equilibrated. The pH was recorded after 24 hours and

plotted against the meq of NaOH.

91

RESULTS AND DISCUSSION

X-ray diffraction analysis

X-ray diffractogram of three different samples

are shown in (Figure 4.1). [Fig. 4.1(a)J shows LDH

starting layered material with three harmonics, d ^ ,

^006' "" ^OOQ S ® Sharp intensity peaks corresponding

to the basal spacing of 29 angles at 7.7X, 3.7A and

2.4X, respectively. The two harmonics d^^^ and d _ of

low intensities at higher 29 angles are 1.59A and 1.58A

respectively {Table 4.1). There is substantial

variation in the basal spacing, when LDH-startlng

material interacts with sulfamic acid or dodecylamine.

In case of sulfamic acid,[Fig. 4.1(b)]the peaks due to

dpQg, dpQg and d „ are shifted to a lower 29 angles

when compared with XRD of [Fig. 4.1 (a )] . For example the

diffraction lines at dQ^-, d^pg and dp-g shift from 7.7

to 16.2A, 3.7 to 8.2A, and 2.4 to 3.2A. This shifting

is attributed to the formation of intercalation of

sulfamic acid to the LDH layered material. Two more

diffraction peaks with low intensities at higher 29

angle has also been observed at d^_.„ and ^(]^7

reflections with basal spacing of 3.2^ and 2.7A,

respectively (Table 4.2). The value at 3.2A suggests

92

29 DEGREES

FIG. 4.1 X-ray diffraction of LDH-starting( a ) , LDH-sulfamlc acicl(b) and LDH-dodecylamine(c).

93

Table 4.1

X-ray data for starting LDH: Calculation of d values Monochromatic Radiation Used: Cu-Kot = 1.54A

PLANE OF REFLECTION

dpQg (1st order)

dpQg (2nd order)

dpQg (3rd order)

^110

d 113

ANGLE OF OBSERVATION (26 degree)

12

24.5

38.4

75.5

76.5.

SPACING BETWEEN THE PLANES (d values in A)

7.7

3.7

2.4

1.59

1.58

94

Table 4.2

X-ray data for LDH-sulfamlc acid : Calculation of d values. Monochromatic Radiation Used: Cu-Ko: = 1.54A

PLANE OF REFLECTION

% 0 3 ^ ^ ^ * °'''^®'"^ '

dQQg(2nd o r d e r )

dpQgOrd o r d e r )

^^0012

^^012

'^llO

ANGLE OF OBSERVATION ( 2 9 d e g r e e )

5.5

10.8

13 .0

26

35

70

SPACING BETWEEN THE PLANES ^ (d v a l u e s i n A)

16 .2

8.2

6.2

3.2

2.7

1.6

95

Table 4.3

X-ray data for LDH-Dodecylamine : Calculation of d values. Monochromatic Radiation Used: Cu-Kos = l, 5 a

PLANE OF REFLECTION

dpQgClst order)

dQQg(2nd order)

dppgOrd order)

^^0012

^012

^110

ANGLE OF OBSERVATION (26 degree)

6.7

10.5

14.5

24

36

72

SPACING BETWEEN THE PLANES (d values in X)

13.3

8.5

5.8

3 .8

2.6'

1.6

96

the presence of nitrate ions. This has also been

confirmed by FT-IR studies. [Fig. 4.1(c)] of LDH-

dedecylamlne is similar to LDH-sulfamic acid. The

diffraction lines at d ,-, d-j g, and d„^Q shift from

7.7 to 13.3A, 3.7 to 8.5X, and 2.4 to 5.8A

respectively (Table 4.3).

FT-IR studies

2_ Parent LDH-COr" sample

2-The FT-IR spectrum of parent LDH-CO sample

2-(Figure 4.2) shows the presence of CO , NO , OH /HO or

combination like hydroxycarbonates, hydroxynitrates in

the form of hydrogen bonding attached to the

interlayers of the double salt which balance the excess

positive charge on the particle. The different

frequencies appeared may be cited as follows :

_i The absorption of a broad band at 3480 cm

corresponds to free 0-H stretching mode. The weak

frequencies at 3000, 2940, and 2900 cm"''" may be

attributed to some possible combinations of hydrogen

bonding in the form of hydroxycarbonates and hydroxy-

nitrates. The presence of interlayers water is recorded

at 1635 cm"'' . Two bands for No' at 1389 cm' and 1277

98

cm"" are observed which corresponds to terminal N0~ and

as bridge NO^ between two metal atoms Mg(II) and

Al(III), respectively. The bands recorded at 863, 554

cm and below are due to lattice vibration of Mg-0,

Al-0 stretching and bending modes within the layers.

Intercalation of sulfamic acid

The same free 0-H stretching at 3466 cm

(Figure 4.3) is observed as discussed above. The

position of weak frequencies have become some what

stronger at 3000, 2940 and 2900 cm"''" due to hydrogen

bonding resulting the formation of hydroxycarbonates

and hydroxynitrates. The frequency of interlayer water

-1 -at 1642 cm remains unaltered. The terminal NO. at

_i 1403 cm has no change at the layer, however, three

-1 more frequencies at 1220, 1207, and 1059 cm are

observed which suggest the occupation of sulfamic acid

molecule in the interlayer spacing. These frequencies

are due to asymmetric, symmetric stretching vibration

of S-N/S-0-H of sulfamic acid group. The broader bands

at weak frequencies 750, 610, and 498 cm" suggest

rearrangement of different groups of sulfamic acid with

Mg-0, Al-0 layers. The carbonate interlayer anions are

observed at frequencies 1590, 1560, and 1500 cm in

99

u (0

e (D

l — H

(0

Q

B 3

*-> u

CO

K

CO

O b

100

the form of cluster bands. The cluster of bands at high

frequencies ranging from 3850 to 3700 cm may be

attributed to the degeneracy of 0-H groups in MgO and

AlO (18).

Intercalation of dodecylamine

The frequencies at 3480, 2950, 2933, and 2856

-1 cm are due to free 0-H and CH- stretchings (Figure

4.4). The interlayer water at frequency 1656 cm'

becomes weaker due to its removal from the interlayers.

The terminal NO*! has occupied the same frequency at

-1 1382 cm , suggesting that it remains attached to the

surface layer. In LDH-dodecylamine spectrum a

difference has been marked showing a complete removal

2-of CO and bridging N0„ anions from the interlayer

spacing, and arising out some new frequencies ranging

from 1130 to 1087 cm"-*" attributed to C-N stretching

vibration. The other bands at 856, 568 and 442 cm"

suggest the intercalation of dodecylamine molecule

within Mg-0 and Al-0 layers.

(Figure 4.5) shows the TGA and DTA for

LDH-sulfamic acid sample. A weight loss upto 500°C

occurs in two steps, the first one up to SOCC

101

c •ft

B to

>. 0) T: o

D

E D +-• u 0) a CO

O •-H

_*oxa •OQNa

o o 00

102

o o

o o to

o o in

o o ^

o o CO

o o N

o o T- l

• / " ^

o *-' 0) u ? +* CD t- , K e ' &:

. •n f t

o CO

o 1-1 R a <n

. i - (

3 CO

• i Q • J

<t-i o

e CO t< 00 o E 0)

l A

•

• o M

(%) mSTa/A

i03

represents 16% of the Initial weight sample due to the

removal of surface adsorbed water and dehydroxylation

of 0-H groups. The corresponding DTA profile shows two

exothermic peaks at 300 and 500°C. The second step/

peak, at 500*='C is attributed to elimination of

interlayer H O , C0„ and N0„ anions.

When intercalated sample is soaked overnight in

dilute hydrochloric acid, the amine group of

dodecylamine or sulfamic acid get protonated and form a

coordinative ionic sphere with positive charge

hydronium ion. In case of transition metal ions, this

coordinative ionic sphere is exchanged with transition

metal leaving behind the hydronium ion in the mother

liquor which have been determined against standard

sodium hydroxide solution by pH-metry. This gives the

idea of sorption capacities summarized in (Table 4.4).

The LDH-dodecylamine has been found to have a

remarkable complexing behaviour with transition metal

ions. This behaviour is illustrated by the pH-titration

2 + curves for the Cu ions (Figure 4.6). From the shape

2 + of the curves, increasing amounts of Cu are taken by

the LDH-dodecylamine. The solid slowly transforms from

white to bright blue in the process. This further

confirms the formation of a copper(II) complex with

amino group in the aquo-metal coordination sphere (19).

104

Table 4.4

Sorption capacity of some metal ions on (A) LDH-sulfamic acid and (B)

LDH-Dodecylamine intercalation compounds.

S.NO.

1 .

2.

3 .

4 .

5.

6.

7,

8.

9.

10.

METAL ION

Mn2*

Co2^

Ni2*

n 2+ Cu

Zn2-

Cd2-

Hg^*

Pb^^

Mg2-

Ba2-

SORPTION CAPACITY (m mol/g)

A

0.13

0.32

0.20

0.14

0.05

0.15

-

0.20

0.13

0.18

B

0.24

0.35

0.25

0.26

0.25

0.19

0.06

0.23

0.25

0.20

105

11

10

9

6

7 X

°- 6

5

-

- /cr

1 1 1

i3

1 1 1 1 1 1

( A ) ( B )

1 2 3 A 5 6 7 MEQ BASE/G

8 10

FIG. 4.6 p H - t i t r a t i o n of (A) LDH-dodecylamine

and the same compound w i t h (B) 0 .01 M

of Cu 2 + added .

106

REFERENCES

1. W.T. Reichle, Clays Miner., 35, 401 (1985).

2. A. Weiss, Angew. Chem. , Int. Ed. Engl., 20, 850 (1981).

3. J.M. Adams, Appl. Clay Sci., 2, 309 (1987).

4. R.M. Barrer, Zeolites and Clay Minerals as Sorbents and Molecular Sieves; Academic Press: New York (1978).

5. T.J. Pinnavaia, Science (Washington, D.C.), 220, 365-371 (1983).

6. C.B. Koch and S. Morup, Clay Miner., 26, 577 (1991).

7. S. Miyata, Clays Clay Miner., 31, 305 (1983).

8. A, Manabe and S. Miyata, U.S. Patent, 4, 458, 030 (1984).

9. W. Jones, M. Chihwe, In Pillared Layered Structures; Mitchell, I.V., Ed.; Elsevier: London (199); p. 67.

10. F. Cavani, F. Trifiro, A. Vaccari , Catal. Today, 11, 173 (1991) and references therein.

11. T. Kwon, G.A. Tsigdinos, and T.J. Pinnavaia, J. Am. Chem. Soc, 110, 3653 (1988).

12. M.A. Drezdzon, Inorg. Chem., 27, 4628 (1988).

13. T. Kwon and T.J. Pinnavaia, Chem. Mater., 1, 381 (1989).

14'. U.S. Patent 4842168 (1989).

15. W.T. Reichle, S.Y. Kang, and D.S. Everhardt, J.-Catal. , 101, 353 (1986) .

107

16. D.L. Bish, Bull. Mineral., 103, 170 (1980).

17. K. Chibwe and W. Jones, J. Chem. Soc,, Chem. Commun., 926 (1989) .

18. J.R. Anderson and M. Boudart, "Catalysis", Springer-Verlag, Berlin Heidelberg New York, 4 (1983).

19. C.Y. Ortiz-Avila, C. Bhardwaj, and A. Clearfield, Inorg. Chem., 33, 2499 (1994).

CiKi'ifP'I*E5i y^lV%

Novel Thin-Layer Chromatographic System Indentification and Separation

of some Cephalosporins on Layered Double Hydroxides-Silica

Gel Mixed Layers.

108

Inorganic ion-exchangers in thin-layer

chromatography have been used for the separation of

metal ions, anions, and organic compounds, in which

promising results have been achieved (1). Now-a-days,

layered double hydroxides (LDH) have been found of much

interest, because of their wide applications especially

in pharmaceutical scienceo Having being highly reactive

surfaces, they are used as adsorbent, catalysis, and

anion scavengers (2). Layered double hydroxides consist

of positively charged brucite-like layers, where

partial substitution of M(II) cations by M(III) has

occurred, with the formula

(' §2 44 ^^^°"^0.88 ^^°3^0.5^-""2° ^^^ ' ^ ° ^ example, in 2 + brucite layer [Mg (0H)„], Mg ions are partly replaced

by Al ions, leaving behind a net positive charge on

the layer structure compensated by anions such as Cl~,

2-OH , COo and water, called interlayer anions, which

occupy the interlayer space. These anions are easily

exchangeable with an equivalent amount of the other

anions and hence, regarded as inorganic anion

exchangers. They are more selective towards anions with

high valency and smaller ionic size. Not only inorganic

anions but also organic anions such as dicarboxylic

acids, acetic acid, and alkyl sulfates have been

exchanged using double layer hydroxides.

109

Double hydroxide compounds normally synthesized

by precipitation of a solution of M and M salts

with base (normally NaOH, KOH, or NH ) , or a solution

of metal salt and a solid hydroxide or oxide of either

M or M is used as reactants. If no precautions are

taken to exclude CO from the • system , carbonate forms

are synthesized. These are the most crystalline and may

be used as starting materials for preparing other

anionic forms (4,5). The precipitation may be carried

out at high pH by mixing the solution of the di- and

trivalent metal salt with an excess of strong base.

However, in many cases the precipitation is carried out

at fixed pH or a final maximum pH is achieved. Taylor

and McKenzie (6) developed a constant-pH precipitation

method called "induced hydrolysis" by which a freshly

precipitated hydroxide of the trivalent metal at fixed

pH was reacted with a metal salt solution of the

divalent metal at the same pH.

2+ 3 + The role of (Mg -Al ) double hydroxide

surface in the adsorption of inorganic and organic

anions did not receive much attention and therefore,

the adsorption on its surface is not yet clear;

however, it contribute to the appearance of the strong

110

basic sites on the double hydroxide surface. Therefore,

the surface may have two kinds of basic sites : a

2-strong basic site, 0 , and a weak basic site, OH .

Consequently, the probable active site might be

attributed to the strong basic surface oxygen.

The cephalosporin antibiotics (CFs) form a

large family of therapeutically useful compounds.

Sporadic number of publications on the identification

of cephalosporin compounds by planar chromatography has

appeared in the literature (7-10). Earlier work with a

number of cephalosporins has been reviewed (11). In

recent years more fruitful results have been emerged to

produce more efficient separation on silanized silica

gel (12, 13).

In this chapter, we describe the use of the

layered double hydroxides (LDH) mixed with silica gel

as coating material in TLC. A large variety of solvent

systems containing buffer solution and organic solvent

have been tried to Investigate the possibility of

separation of some selected cephalosporin compounds.

I l l

EXPERIMENTAL

Chemicals

Methanol, ethylacetate, dimethylsulfoxide, and

tetrahydrofuran were obtained from Merck. Acetonitrile

and cyclohexane from Ranbaxy. Methylacetate from G.S.C.

(India). Chloroform, formic acid, sulfuric acid and

acetone from Glaxo (India).

Samples

The cephalosporins studied were of current

production quality. Cefadroxil monohydrate and

ceftriaxone sodium were obtained from Aristo;

Cefuroxime sodium and ceftazidime from Glaxo;

Cefotaxime sodium from Taxim and cephalexin C from

Ranbaxy.

Preparation of Plates

Preparation of layered double hydroxides and

their layer plates : Layered double hydroxides of Al

2 + and Mg prepared according to the previously reported

method (14). A slurry was prepared by suspending the double

hydroxide powder mixed with silica gel G in distilled

112

vuater in the ratio of 2:1. The chromatopiates (20x20

cm) were coated to a thickness of 0.5 mm using a

standard Desaga spreader. The plates were dried at room

temperature and activated at 105°C for 30 min.

Solvent systems

All ratios are expressed in volumes. The buffer

solution consisted of a 15 per cent (w/v) solution of

ammonium acetate adjusted to pH 6.2 with glacial acetic

acid.

(M ) 100 parts of buffer solution.

'2 (M^) 80 parts of buffer solution with 20 parts of

methanol.

(M ) 60 parts of buffer solution with 40 parts of

methanol.

(M ) 40 parts of buffer solution with 60 parts of

methanol.

(M_) 20 parts of buffer solution with 80 parts of

methanol.

(M ) 100 parts of methanol.

(M_) 85 parts of buffer solution with 10 parts of

methanol and 5 parts of acetonitrile.

(MQ) 85 parts of buffer solution with 15 parts of o

acetonitrile.

113

(M ) 85 parts of buffer solution with 15 parts of

methylacetate.

(M ) 85 parts of buffer solution with 15 parts of

dry ether.

(M ) 85 parts of buffer solution with 15 parts of

petroleum spirit (ether).

(M._) 100 parts of chloroform.

(M^„) 100 parts of cyclohexane.

(M ) 100 parts of dimethylsulphoxide (DMSO).

(M.^) 80 parts of dimethylsulphoxide with 20 parts of 15

distilled water.

(M.„) 85 parts of dimethylsulphoxide with 10 parts of

distilled water and 05 parts of formic acid.

(M ) 85 parts of buffer solution with 15 parts of

acetone.

(M.£,) 85 parts of buffer solution with 15 parts of

tetrahydrofuran.

ChromatoRraphic Procedure

For qualitative studies, aliquots of solutions

containing 10 mg/ml of each cephalosporin were applied

to the plate. Doubly distilled water being used as the

solvent for all the cephalosporins. The chromatographic

chambers were lined with filter paper and conditioned

114

vW th appropriate solvent system for at least 1 hr prior

to use. The plates were developed upto a distance of 14

cm from the starting line, at room temperature and air

dried. The spots were detected with iodine vapor as

detecting reagent. The R„ values were calculated, using

the following formula

% = log ( i - 1)

115

RESULTS AND DISCUSSION

The hRf (RfxlOO) of cephalosporins obtained on

double hydroxide-silica gel layers with eighteen

different mobile phases have been summarized in Table

5M, which reflects that identification and separation

of various cephalosporins in selected solvent system.

The use of thin-layer of double hydroxides mixed with

silica gel G gives improved results compared with

silica gel only; it also shows considerable movement of

molecules with compact spots. Moreover, conditions are

optimised for the separation of cephalosporins, "and

hence, best separations are obtained by a judicious

choice of the four mobile phases M_, M„, M- and M^ p •

However, it is observed that some of the mobile phases

yield tailing spots. The results of this study have

been interpreted as follows :

(i) Buffer system without organic solvent[B; Mj: In

this system most of the cephalosporin compounds are

lipophilic that is they do not move appreciably. As the

concentration of methanol is increased from 20% to 100%

[BM; M„ to M l , the lipophilic nature of compounds

increases.

116

(ii) Addition of acetonitrile (5%) [BMA; M ] : The

ceftriaxone shows lipophobic where others not. However,

increasing the composition of acetonitrile from 5 to

15% (and removing methanol from the solvent mixture;

M-), the lipophobic nature of ceftriaxone remains

unaltered while the rest of the compounds move slightly

(compare with M ).

(iii) Addition of methylacetate (15%)[BMeAe; M ] : All

the cephalosporin compounds are lipophilic.

(iv) Addition of ether and petroleum ether (15% each)

[BE 5 BPE; M^ Q S M^ ] : Lipophilic in all the cases

except ceftriaxone.

(v) In chloroform (100%) [Ch; M J: Spots are tailed.

(vi) In cyclohexane (100%)E:; M ] : Spots are tailed. J- O

(vii) In dimethylsulphoxide and water (100% and 90%).

[Di, DiW; M.. S M. ]: Spots are tailed.

(viii) In acetone (15%) [BAc; M ] : All the compounds

are lipophilic and spots are compact.

(ix) In tetrahydrofurane (15%) [BT; M ]: Spots are

tailed.

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119

In both acidic and basic pH's M ; pH 4.7 8

M^ ,; pH 10.5, the cephalosporin compounds show R,

values with considerable tailing. This indicates that

the solvent systems with neutral pH's provide more

favourable conditions to give compact spots.

The effect of methanol concentrations in the

mobile phases (M to M_) with respect to R^ values are

reported in Table 5.2. Higher and/or positive R values

indicate compounds move lipophilic than those

represented by lower and/or negative R„ values. Figure

5.2 shows that for each compound there is a linear

relationship between the R., values and the composition M

of the mobile phase over a considerable range of

methanol concentration. Such relation was previously

demonstrated by Soczewinski and Wachtmeister (15)

between the R^ values of phenolic compounds and a

mobile phase consisting of various concentrations of

dimethylsulphoxide in water. The practical importance

of this relationship is that it allows to calculate the

theoretical values of R., for each compound, provided

the solvent system does not deviate very much from

ideal behaviour.

The R .f values of cephalosporin compounds are

also plotted against the composition of the mobile

120

0.9

0.8

0.7

0,6

S 0.5 -

> 0.4 i

0.3

0.2

0.1

Cefotaxime

'• •< '' '• ' 1

20 40 60 80

Methanol Concentration

100

Figuire S.l

The R_ values of the cephalosporins tested are plotted

against the composition of the mobile phase.

121

m 0) r-l (0 >

«

i.d

0.5-

-0.5

-1.0

A Ceftriaxone o Cefuroxime o Cefotaxime • Ceftazidime *« Cefadroxil n cefalexin

I 1 r —

20 -40 60 80

Methanol concentration

^ «

S

100

Figure 5.2

The Rj values are plotted against the composition of the

mobile phase.

122

phase (Figure 2.1). It can be seen that R, values

increase in methanol concentration in the mobile phase

for each compound.

The coating material consists of Lewis acid

centres (surface Al S Mg ions), with coordinated

water through a Idne pair of electrons at the oxygen

2-atom, and Lewis base centres (surface 0 ions), which

abstract the proton. When a partially hydroxylated

active-mixed surface is probed with cephalosporins,

several hydrogen-bonded species of different bond

strength are formed arising from the amphoteric

character on the surface, which is demonstrated by the

variation observed in the hydrophilic nature of the

tested compounds. However, there are several ways in

which such organic compounds can interact with the

surface. The main interaction modes observed may be

attributed to the Bronsted acidity of the surface

groups, which gives a specific adsorption of

cephalosporin compounds on certain sites on the mixed

surface.

The use of inorganic salts (e.g. sodium

chloride, cesium chloride, and lithium chloride) has

been made to check the degradation of silica gel

coating. Sodium chloride reduces the solubility of

123

silica and/or binder In sodium chloride solution

compared to water. In addition to this, the use of

sodium chloride with organic solvents has been reported

to give improved separation compared to untreated

solvents (16, 17).

It has already been discussed in the

introductory part that the double layer hydroxides

possess exchange capability for both organic and

inorganic anions. The framework consists of pillared

2 — like structure, in which anions e.g., CO. and water

occupy interlayer space, and can be exchanged by

organic neutral or anionic species. The cephalosporin

compounds in buffer system may acquire a negative/

positive charge and can act as neutral species. Hence,

2-the possibility of their exchange with H-O/COr" can not

be ruled out. Moreover, the silica gel surface provide

the physical interaction during the development of the

cephalosporin compounds.

Another possibility of interaction is the

adsorption of compounds on the silica gel surface. The

hydroxylated silica gel surface can provide different

types of Si-OH (silanol) groups which depends on the

type of material and thermal pretreatment. The OH

124

groups present on partially hydroxylated silica surface

are weakly acidic. Hence, they react with a bases such

as H O to give hydrogen bonded s.llanol pairs. The main

part of the fully dehydroxylate silica surface is shown

to be unreactive because of the corresponding homopolar

character of Si Si groups (18).

125

REFERENCES

1. 'Handbook of Thin Layer Chromatography', J. Sherma and B. Fried, Eds., Marcel Dekker, Inc., New York, 1990.

2. F. Cavani, F. Trlfflro, and A. Vaccari, Catal. Today, 11 (1991), 173.

3. V.R.L. Constantino and T.J. Pinnavia, Inorg. Chem., 34, (1995), 883.

4. T. Sato, T. Wakabayashi, and M. Shimada, Ind. Eng. Chem. Prod. Res. Dev., 25 (1986) 89.

5. H.C.B. Hasen and R.M. Taylor, Clay Miner., 26 (1991) 311.

6. R.M. Taylor and R.M. McKenzie, Clays. Clay Miner., 28 (1980) 179.

7. C.J. Budd, J. Chromatogr., 76 (1973) 509.

8. I.J. McGitveray and R.D. Strickland, J. Pharm. Sci., 56 (1967) 77.

9. J. Vandamme and J.P. Voets, J. Chromatogr., 71 (1972) 141.

10. J.R. Fooks and G.L. Mattok, J. Pharm. Sci., 58 (1969) 1357.

11. D.W. Hughes, A. Vilim, and W.E. Wilson, Can. J. Pharm. Sci., 11 (1976) 97.

12. J. Hoogmartens and E. Roets, J. Assoc. Off. Anal. Chem,, 46 (1981) 173.

13. I. Quintens, J. Eykens, E. Rocts, and J. Hoogmartens, J. Planar Chromatog., 6 (1993) 181.

14. V.R.I. Constantino and T.J. Pinnavaia, Catal. Lett., 23 (1994) 361.

126

15. E. Soczpwinskl and C.A. Wachtmelster, J, ChromatogF., 7 (1962) 311.

16. J.A. Mantbey and M.E. Amundson, J. Chromatogr., 19 (1965) 522.

17. C.J. Budd, J. Chromatog., 76 (1973) 509.

18. J.R. Anderson and M. Boudart : "Catalysis", Springer Verlag, Berlin Heidelberg, New York, 4, (1983) 71,

127

LIST OF PUBLICATIONS

A. Original full papers

1. S.Z. Qureshi, Rasheed M.A.Q. Jamhour and N. Rahman "Intercalation of Dodecylamine and Sulfamic Acid Into Layered Double Hydroxide", Annales de Chimle, (France) In press .

2. S.Z. Qureshi, Rasheed M.A.Q. Jamhour and N. Rahman "Surface Interaction of Ethanolamlne with Hydrous Zirconium(IV) oxide Gel: Characterization And Separation of Siome Anionic Species By Column Chromatography", Annales de Chimle, (France) In p r e s s .

3. S.Z. Qureshi, Rasheed, M.A.Q. Jamhour and N. Rahman "A Novel Thin-Layer Chromatographic System : Indentification and Separation of Some Cephalosporins", J. P lanar Chromatography-Modern TLC, (Hungary) In press .

4. S.Z. Qureshi, Rasheed M.A.Q. Jamhour and N. Rahman "Thin-Layer Chromatographic Behaviour of Carbamate Pesticides and Related Compounds on Zirconium Phosphate Layers", Anal. Chim. (Warsaw) - In press .

B. Conference presentations

1. Rasheed M.A.Q. Jamhour "Interact ion of Ethanolamine with Zirconium Oxychloride; A Route Leading to A New Class of Inorganic Ion-Exchanges", Abstract book of IICT Golden Jubilee on "New Horizons In Analytical Chemistry", Indian Inst i tute of Chemical Technology, 23-24, 02, 1995, Hyderabad, Ind ia , p . 22.

2. Rasheed M.A.Q. Jamhour "Novel Thin-Layer Chromatographic System : Identification And Separation of Some Cephalosporins", Book of Abstracts of the 14th Conference of The Indian Council of Chemists a t The Ins t i tu te of Science, Bombay, India , 29-30, 12, 1995, No. AO-40, p . 17.

3. Rasheed M.A.Q. Jamhour "Study on the Effect of Anions in Molecular Complexes", Book of Abstracts, Department of Chemistry, Allgarh Muslim University, Aligarh, I n d i a , 18-20.03.1996, p . 13.