Titrimetric Potentiometric Determination of Anionic and Cationic Surfactants

8/13/2019 Titrimetric Potentiometric Determination of Anionic and Cationic Surfactants

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No. 233/3 e

Application BulletinOf interest to: General analytical laboratories A 1, 3, 4, 12

Detergents, surfactants and cosmetics

Pharmaceutical industry

Titrimetric/potentiometric determination of anionicand cationic surfactants

Summary

Surfactant analysis plays a major role worldwide. Whether in formulations or start-ing products the content should be determined as quickly, precisely and accu-rately as possible. The two-phase titration according to Epton employs chloro-form, a solvent that is now rightly taboo. Further, in some cases the equivalencepoint is difficult to detect and the titration cannot be automated. This method alsorequires a great deal of analytical experience.

The surfactant ISE provides help here in many cases and also benefits the envi-ronment. It has been specially developed for surfactant determinations using po-tentiometric indication and has already been tested in thousands of titrations incombination with a sample changer.

Anionic surfactants can be titrated with cationic surfactants and vice versa. ThisBulletin describes a wide range of substances that can be determined and lists the

relevant working conditions and parameters. Moreover, a titrant for anionic surfac-tants is introduced that provides larger and steeper potential jumps and hence im-proves the precision of the determinations when used in conjunction with the sur-factant ISE and the titrator.

Theory behind the electrode

The surfactant ISE electrode is a PVC liquid membrane electrode with a mem-brane composition (ionophore/plasticizer) that has been specially optimized for thedetermination of ionic surfactants. The electrode potential is due to a specific inter-action between the ion carrier incorporated in the PVC membrane and the analyteions (surfactants) in the analysis solution. This interaction leads in an equilibrium

reaction to a potential crossing of the analyte ions from the analysis solution intothe membrane and as a result of this to the formation of an electrical potentialdifference at the phase boundary analysis solution/membrane, which can bemeasured at zero current (potentiometrically) against a reference electrode. Theextent of ion transfer from the analysis solution into the membrane depends on theconcentration. The relation between the analyte ion concentration and the electricalpotential is described by the Nernst equation:

E = E0 + s * lg aM

In the equation, s represents the electrode slope. In the ideal case it is ca. 59mV per concentration decade for monovalent anions and cations at 25 C. In prac-tice, lower slopes are frequently observed.


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Application Bulletin No. 233/3 e

Determination of anionic and cationic surfactants Page 2

Owing to a variety of circumstances (membrane composition, special properties ofthe surfactants such as boundary activity, substantivity [= tendency to absorb onsurfaces], formation of micelles), Nernstian behaviour cannot always be assumedfor the High Sense electrode. In practice, this means that

the electrode is not suitable for direct potentiometric concentration determina-tions and

the titration should always be evaluated using the inflection point of the S-shaped titration curve. Equivalence point titrations are usually not to be recom-mended.

Instruments and accessories

For example: Titrinos 702 or 716 or 736 or 751 or Titroprocessor 726, 727 Titra-tion Stand, 722 Propeller Rod Stirrer as well as eventual a printer with appropri-ate printer cable

Exchange unit 6.3014.223

Ionic surfactant electrode 6.0507.120 and reference electrode 6.0726.100 (KCl,c = 3 mol/L) with appropriate electrode cables

Reagents

Buffer solution pH = 2.0 citrate/HCl, e.g. Merck Titrisol no. 109882

Buffer solution pH = 3.0 citrate/HCl, e.g. Merck Titrisol no. 109883

Buffer solution pH = 6.0 citrate/NaOH, e.g. Merck Titrisol no. 109886

Buffer solution pH = 7.0 phosphate, e.g. Metrohm no. 6.2305.020

Buffer solution pH = 10.0 boric acid /KCl/NaOH, e.g. Merck Titrisolno. 109890

Hydrochloric acid c(HCl) = 2 mol/Land c(HCl) = 0.1 mol/Las well as so-dium hydroxide c(NaOH) = 2 mol/L(to adjust to other pH values)

Methanol puriss p.a. and distilled or demineralized water

Titrants

General

The selection of the titrant is very important. The lower the solubility of the com-pounds formed (the greater their oleophilic properties), the larger and steeperthe potential jump of the titration curve. Advantage should be taken of this effectwhen formulations are titrated. (Additives can lead to considerable flattening of

the potential jumps.)Work is preferably performed with titrants of concentration 0.004 mol/L; only inexceptional cases is a concentration of 0.01 mol/L used.

The weight of titrant required is given by:

Weight [in g] = Mr* 0.004 (or * 0.01) to 1 liter

Weigh in the required amount (plus slight excess*) exactly and dissolve in dist.water, warming gently if necessary. Make up to 1 liter with dist. water at 20 C.The titer is determined against an anionic or cationic surfactant. As long as thesolution in the reagent bottle and the Exchange Unit has not stabilised, the titeris also not stable (surfactants are substantive, i.e. they tend to adhere to sur-faces; this applies particularly to cationic surfactants). Consequently, use al-ways the same reagent bottles and Exchange Units and allow the solution tostand for 1 day before determining the titer.

*) By their nature, the substances do not contain 100 % active substance. The major by-product isusually water. The water mass fraction can amount to up to 8 % and is very difficult to remove.It is essential to take these circumstances into account when weighing in the titrant.


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Titrants for anionic surfactants

a) TEGOtrant A 100: 1,3-didecyl-2-methylimidazolium chloride (DDMICl);Mr= 399.7 g/mol; Metrohm no. 6.2317.000 (6 g) or 6.2317.010 (60 g)

b) Hexadecylpyridinium chloride (HDPCl), also called cetylpyridinium chloride(CPCl); Mr= 358.01 g/mol; Fluka no. 52 349

c) Hyamine1622 (benzethonium chloride); Mr= 448.10 g/mol; Merck no.112058

Titrants for cationic surfactants

a) Sodium dodecylsulfate (sodium lauryl sulfate LAS); Mr= 288.38 g/mol;Merck no. 112533 or Fluka no. 71 727; stabilized against bacterial attack by0.5 % formaldehyde.

Note: Extensive investigations over a considerable period of time haveshown that the content of the Merck product is 99.2 % (rest: water, sodiumsulfate and lauryl alcohol).

b) Dioctylsodium sulfosuccinate (DOS) (bis(2-ethylhexyl)-sodium sulfosucci-nate); Mr= 444.57 g/mol; Fluka no. 86 139

Note: May saponify at higher pH values (shelf life still unknown)!

c) For certain applications: sodium tetraphenylborate; Mr= 342.23 g/mol;Merck no. 106669

Note: Caution! Reacts with potassium and ammonium ions and with certainamines. Use sodium chloride (c(NaCl) = 1 mol/L) as bridge electrolyte(6.0726.100 reference electrode). Titer may not be stable.

Preparation, maintenance and storage of the surfactant electrode

The electrode is stored dry. The electrode is best conditioned by two to three titrations whose results should

be ignored.

Adherent deposits are removed with a soft paper towel, moistened in methanol.In sample changer operation, the electrodes are dipped briefly in methanol,while stirring.

The electrode is not resistant towards almost any organic solvents (PVC mem-brane). Chloroform, hydrocarbons, acetone, MIBK, tetrahydofuran, etc. destroythe electrode. High proportions of methanol (30...40 %) or ethanol (20 %) in thesolvent shorten the lifetime of the electrode.

Several thousand titrations can be performed with the electrode under normal

conditions. Evidence of a decrease in the responding behaviour of the electrodeis shown in flatter titration curves and a shortened potential range. For a shorttime, such an electrode can be regenerated by submerging it for 30 min. in asodium lauryl sulfate solution (0.004 mol/L). If this does not help, the electrodemust be replaced.


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pH ranges for some detergents

Anionic surfactants

Titration recommendations for anionic surfactants

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

pH value of the titration solution

Tir

Titration not possible

Titration possible

Recommended for titration

Sulfates

Sulfonates

Carboxylates (soaps)

Sulfosuccinates(SO3)

Sulfosuccinates(SO3+ COOH)

In the case of samples that contain both sulfosuccinates and betaines, the sul-fosuccinates are titrated at pH = 3.0.

For the determination of sulfosuccinates, the following pH values are selected: sulfonate group at pH = 2.0 sulfonate and carboxylate group at pH = 10.0.

Cationic surfactants

Titration recommendations for cationic surfactants

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

pH value of the titration solution

Tir

Titration not possible

Titration possible

Recommended for titration

Quats

Ester quats

Fatty amines

Fatty amines /Adducts of EO


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For the determination of the degree of quarternization, an additional titration isperformed at pH = 3.0 to obtain the sum of the quaternary ammonium com-pounds and the tertiary starting amine.

The ester quats contained in softeners are usually titrated at pH = 2.0. How-

ever, some ester quats exhibit their greatest stability at pH = 5 or pH = 7 andshould thus be determined at these pH values. Here, it should be noted that thepH has to be adjusted immediately following the sample weighing. Slightly alka-line conditions can very quickly lead to ester cleavage resulting in the ester los-ing its surfactant properties. This would lead to erroneous results.

Betaines and amphoteric surfactants cannot be titrated. However, when presentin the protonated form (at pH = 0...1), they can interfere with the determinationof other surfactants.

Analysis

The dynamic titration (DET) is the most suitable as it allows the fastest titrations

and offers the best reproducibilities. However, titrations can naturally also be per-formed in the MET or GET mode.

An amount of sample that corresponds to a titrant consumption of at least 10 mL isweighed into a beaker and ca. 50 mL dist. water are added. Following addition of10 mL buffer solution and 5 mL methanol, the titration is started (examples in theappendix). In the case of concentrates and raw materials, for reasons of accuracya dilution should first be performed. In order to prevent formation of micelles, about10...50 % methanol are added. An aliquot of the initial dilution is then used for thetitration (take into account the methanol fraction of the initial dilution).

Anionic surfactants

Anionic surfactants are normally titrated with a cationic surfactant at pH = 3.0.

For special cases, see the corresponding graph. True, soluble soaps (sodium or potassium salts of higher fatty acids) must be ti-

trated with TEGOtrant A 100 at pH values > 10. Other cationic titrants producepoor titration curves that are often impossible to evaluate. In mixtures, anionicsurfactants and soaps are determined as a sum. With decreasing pH value, thefraction of the soaps determined by titration becomes increasingly smaller.Complete separation is achieved by acidifying the sample to pH = 2.0 (allow thesample to stand 13...30 min for the reaction to run to completion). In the titrationwith TEGOtrant A 100 only the anionic surfactants are then determined. ThepH value for the sum titration depends on the sample used and must be deter-mined by preliminary titrations (pH = 10...13). Two potential jumps result withthe second being used to determine the sum of the soaps and anionic surfac-tants.

Cationic surfactants

Cationic surfactants are normally titrated with an anionic surfactant at pH =10.0. For special cases, see the corresponding graph.

Samples that contain amine hydrochlorides are titrated at pH = 3.0 if this classof substances needs to be detected. On the other hand, if the content withoutamine hydrochlorides is required, work is performed at pH = 10.0.


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Calculation

1 mL anionic surfactant 0.004 mol/L = 1.5988 mg DDMICl

= 1.4320 mg HDPCl

= 1.7924 mg Hyamine1622

= 0.0560 mg surfactant-N

1 mL cationic surfactant 0.004 mol/L = 1.1535 mg sodium dodecylsulfate

= 0.1280 mg surfactant-S

Comments

If the electrode is left in the titrated sample solution for too long, in the next titra-tion it will either not respond at all or wrongly. In such cases, rinse with metha-nol and place in 0.004 mol/L sodium dodecylsulfate solution for a few minutes.

It is always advisable to immerse the electrode in the sample solution for 20...40s before each titration to allow adjustment to the sample matrix.

You can extend the lifetime of the electrode by storing it dry.

The titrant TEGOtrant A 100 provides much steeper titration curves and largerpotential jumps than other titrants. These advantages are particularly apparentwith surfactants and soaps that produce only very weak potential jumps that aredifficult to evaluate, for instance with Hyamine1622. In contrast to Hyamine1622, with TEGOtrant A 100 lower detergent concentrations can thus be de-termined. However, exercise caution in this connection as the values may betoo low.

If sufficient sample is available, the sample weight should be chosen to producea titrant consumption of at least 10 mL. Only this guarantees determination ofthe total amount of surfactants. While lower sample weights give better titrationcurves, they sometimes lead to values that are too low.

Addition of methanol is absolutely necessary, particularly in finished formula-tions (e.g. shampoos, shower gels, softeners). In some cases it may even benecessary to increase the methanol content drastically in order to obtain preciseresults. Possible micelle and foam formation can be prevented in this way (seealso examples in the appendix).

The determination limit for ionic surfactants in waste waters, for example, lies atapprox. 3 - 5 mg/L. For this purpose the titrant must be diluted to 0.002 mol/L.Measure 100 mL of the sample solution and ajust its optimum pH value withNaOH or HCl. Do not add methanol!

This electrode is not suitable for fatty or oily products (e.g. drilling and cuttingoils, cooling lubricants, cleaning baths, special household cleaning agents andfurniture polishes, shower gels and bath salts). Here a Surfactrode must beused. Please see Application Bulletin No. 269.


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Practical examples

1. Titration parameters

To achieve optimum evaluation of the titration curves, we recommend to work with

three different titrator settings: one for steep, one for intermediate and one for flattitration curves.

Titration curve

Command steep intermediate flat

MEAS 1 30 s * 30 s * 30 s *

QUANTITY U U U

DRIFT/min 30 mV 50 mV 50 mV

M.DELAY 32 s 26 s 26 s

DYNT 30 s 30 s 30 s

MPT.DENSITY 5 3 2

DOS.RATE/min 30 mL 30 mL 30 mL

f.VRESOL 0.1 % 0.1 % 0.1 %

N.EPs 8 8 8

VOLUME 20 mL 20 mL 20 mL

*) The waiting time of 30 s is needed to allow the electrode to adjust to the titration solution.

2. Analysis of raw materials

2.1 Determination of anionic surfactants

2.1.1 Fatty alcohol ether sulfates

5 % methanol, 10 mL buffer solution pH = 3.0; minimum consumption of TEGO -trant 0.004 mol/L: 10 mL; parameters intermediate titration curve.

2.1.2 Fatty alcohol sulfates

5 % methanol, 10 mL buffer solution pH = 3.0; minimum consumption of TEGO -trant 0.004 mol/L: 10 mL (if based on coconut fat: 12 mL); parameters interme-diate titration curve.

2.1.3 Sulfosuccinate monoesters

5 % methanol, 10 mL buffer solution pH = 1.0 or pH = 2.0 if only the sulfonategroup needs to be determined, 10 mL buffer solution if the sulfonate and carboxy-late groups need to be determined; minimum consumption of TEGOtrant 0.004mol/L: 10 mL; parameters intermediate or flat titration curve (depending on thenumber of POE units); take into consideration the hydrolysis stability of the estergroup!

2.1.4 Sulfosuccinate diesters

5 % methanol, 10 mL buffer solution pH = 3.0; minimum consumption of TEGO -trant 0.004 mol/L: 10 mL; parameters steep titration curve; take into considera-tion the hydrolysis stability of the ester group!

2.1.5 -olefin sulfonates

5 % methanol, 10 mL buffer solution pH = 3.0; minimum consumption of TEGO -trant 0.004 mol/L: 8 mL; parameters intermediate titration curve; values may betoo high in comparison with the two-phase titration*.


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2.1.6 Secondary alkanesulfonates

5 % methanol, 10 mL buffer solution pH = 3.0; minimum consumption of TEGO -trant 0.004 mol/L: 10 mL; parameters intermediate titration curve; values may betoo high in comparison with the two-phase titration*.

2.1.7 Linear alkylbenzene sulfonates5 % methanol, 10 mL buffer solution pH = 3.0; minimum consumption of TEGO -trant 0.004 mol/L: 10 mL; parameters steep titration curve.

2.1.8 Isethionates

10 % methanol, 10 mL buffer solution pH = 3.0; minimum consumption of TEGO -trant 0.004 mol/L: 10 mL; parameters intermediate titration curve.

Dissolve coconut fat isethionates in 5 mL each of methanol and dist. water withgentle warming (allow to stand 3...5 min); then add 90 mL dist. water and 2 mLc(HCl) = 0.1 mol/L and titrate immediately.

*) With the potentiometric titration, it is easily recognized that titration is performed according to de-creasing oleophilic character. In particular, the differentiated titration curve indicates different inflec-tion points with several products (e.g. C-12 C-10 C-8). This could be one of the reasons whysomewhat higher values (up to 3 %) are found in comparison with the two-phase titration.

2.2 Determination of cationic surfactants

2.2.1 Benzalkonium halides

10 % methanol, 10 mL buffer solution pH = 3.0 or pH = 10.0; minimum consump-tion of sodium lauryl sulfate 0.004 mol/L: 6 mL, with bis(2-ethylhexyl)-sodium sulfo-succinate 0.004 mol/L: 4 mL; parameters intermediate titration curve; take intoconsideration the substantivity of the cationic surfactants!

2.2.2 Quaternary ammonium compounds

10 % methanol, 10 mL buffer solution pH = 10.0; minimum consumption of sodium

lauryl sulfate 0.004 mol/L: 10 mL; parameters intermediate titration curve; takeinto consideration the substantivity of the cationic surfactants!

3. Analysis of formulations

3.1. Determination of anionic surfactants in formulations

3.1.1 Rinse-off formulations without sulfosuccinates

Weigh in 100...300 mg sample, add 10 mL buffer solution pH = 5.0 and 40 mL dist.water and dissolve sample, add 5 mL methanol and titrate with TEGOtrant 0.004mol/L; minimum consumption of titrant: 10 mL; depending on the formulation, pa-rameters for intermediate or flat titration curve; perform at least three determi-nations (turbidities caused by pearl lustre concentrates do not interfere).

3.1.2 Rinse-off formulations with sulfosuccinates

Weigh in 100...300 mg sample, add 10 mL buffer solution pH = 3.0 and 40 mL dist.water and dissolve sample, add 5 mL methanol and titrate with TEGOtrant 0.004mol/L; minimum consumption of titrant: 10 mL; depending on the formulation, pa-rameters for intermediate or flat titration curve; perform at least three determi-nations (turbidities caused by pearl lustre concentrates do not interfere).

3.1.3 Mouth wash solutions on a lauryl sulfate basis

To 5...10 g sample add 10 mL buffer solution pH = 3.0 and 30 mL dist. water, thenadd 5 mL methanol and titrate with TEGOtrant 0.004 mol/L; minimum consump-tion of titrant: 10 mL; parameters intermediate titration curve.

3.1.4 Toothpastes on a lauryl sulfate basis

To 1...2 g sample add 10 mL buffer solution pH = 3.0 and 40 mL dist. water, thenhomogenize with ULTRA-TURRAXhigh frequency mixer; rinseULTRA-TURRAXwith 10 mL methanol and titrate sample solution with TEGOtrant 0.004 mol/L;minimum consumption of titrant: 10 mL; parameters intermediate titration curve.


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3.1.5 Anionic surfactants (dioctyl sulfosuccinates) in glass/window cleaningagent

To 6...7 g sample add 10 mL buffer solution pH = 3.0 and 40 mL dist. water, thenadd 5 mL methanol and titrate with TEGOtrant 0.004 mol/L; parameters inter-mediate titration curve.

3.1.6 Anionic surfactants in WC cleaning agent

To 2.5...3.5 g sample add 10 mL buffer solution pH = 3.0 and 40 mL dist. water,then add 10 mL methanol and titrate with TEGOtrant 0.004 mol/L; minimum con-sumption of titrant: 10 mL; parameters steep titration curve.

3.1.7 Anionic surfactants in dishwashing concentrate

To ca. 3 g sample add 10 mL buffer solution pH = 5.0 and 40 mL dist. water, thenadd 10 mL methanol and titrate with TEGOtrant 0.004 mol/L; minimum consump-tion of titrant: 10 mL; parameters steep titration curve.

3.1.8 Anionic surfactants and soaps in all-purpose cleaning agents

To ca. 3 g sample add 10 mL buffer solution pH = 5.0 (for the determination of the

anionic surfactants) or 10 mL buffer solution pH = 10.0 (for the determination of theanionic surfactants and soaps) and 40 mL dist. water; then add 10 mL methanoland titrate with TEGOtrant 0.004 mol/L; minimum consumption of titrant:8 mL; parameters intermediate to flat titration curve.

3.1.9 Sum of the anionic surfactants in a shampoo and shower gel

Weigh ca. 200 mg sample exactly into a beaker and dissolve in 45 mL dist. waterand 3 mL methanol; add 5 mL buffer solution pH = 3.0 and titrate with TEGO trant0.004 mol/L; parameters intermediate (shower gel) to steep titration curve(shampoo); determination performed on the Titroprocessor.

Calculation:

mmol/100 g = E1 * C1 * CM * D1 * C5 / S0 ; 2; mmol/100 g

% surfactant-S = E1 * C1 * CM * C2 * D1 / S0 ; 2; %

E1 = mL TEGOtrant consumed to reach the first EPC1 = 1000C2 = 3.2064 (Mr(S) / 10)C5 = 100CM = 1.013 (titer)D1 = 0.004 (mol/L TEGOtrant)S0 = sample weight in mg


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Titration curve for the determination of the Titration curve for the determination of theanionic surfactants in a shampoo. anionic surfactants in a shower gel.

Results:

The shampoo contains 29.41 mmol/100 g anionic surfactants and 0.94 % surfac-tant-S.The shower gel contains 31.88 mmol/100 g anionic surfactants and 1.02 % surfac-tant-S.

3.2 Determination of cationic surfactants in formulations

3.2.1 Hair conditioner

To 0.5...2 g sample add 10 mL buffer solution pH = 2.0 to pH = 10.0 (test andmatch to the particular formulation) and 40 mL dist. water and homogenize withULTRA-TURRAX; rinse ULTRA-TURRAXwith 10 mL methanol and titrate sam-ple solution with sodium lauryl sulfate 0.004 mol/L; minimum consumption of titrant:10 mL; parameters flat titration curve; take into consideration the substantivity of

the cationic surfactants!

3.2.2 Gargle solution on a benzalkonium basis

To 100...300 mg sample add 10 mL buffer solution pH = 3.0 or pH = 10.0 and 40mL dist. water, then add 10 mL methanol and titrate with bis(2-ethylhexyl)-sodiumsulfosuccinate 0.004 mol/L; minimum consumption of titrant: 10 mL; parametersintermediate titration curve; take into consideration the substantivity of the cati-onic surfactants!

3.2.3 Mouth/dental wash solutions on an amino fluoride basis

To 5...10 g sample add 10 mL buffer solution pH = 3.0 and 30 mL dist. water, thenadd 10 mL methanol and titrate with bis(2-ethylhexyl)-sodium sulfosuccinate 0.004mol/L; minimum consumption of titrant: 10 mL; parameters flat titration curve;

take into consideration the substantivity of the cationic surfactants!


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3.2.4 Toothpastes on an amino fluoride basis

To 1...2 g sample add 10 mL buffer solution pH = 3.0 and 40 mL dist. water andhomogenize with ULTRA-TURRAX; rinse ULTRA-TURRAXwith 10 mL methanoland titrate sample solution with sodium lauryl sulfate 0.004 mol/L; minimum con-sumption of titrant: 10 mL; parameters flat titration curve.

3.2.5 Cationic surfactants (ester quats) in a fabric softener

Dissolve ca. 1 g sample in 90 mL dist. water and 5 mL methanol; add 5 mL buffersolution pH = 3.0 and 1 mL c(HCl) = 2 mol/L and titrate with dioctylsodium sulfo-succinate 0.01 mol/L; parameters flat titration curve (see also the parameter re-port of the 716 DMS Titrino with the corresponding settings).

Calculation:

meq/g ester quats = EP1 * C01 * C02 / C00 ; 4; meq/g

EP1 = mL dioctylsodium sulfosuccinate consumed to reach the first equivalencepoint

C00 = sample weight in gC01 = 0.01 (mol/L dioctylsodium sulfosuccinate)

C02 = titer

Parameter report of the 716 DMS Titrino Titration curve for the analysis ofthe fabric softener.

3.2.6 Cetylpyridinium chloride (CPCl) in a mouth/dental wash solution

Pipet 10.0 mL sample into a beaker, add 40 mL dist. water and 5 mL buffer solu-tion pH = 3.0 and titrate with sodium dodecylsulfate 0.004 mol/L; determination per-formed on the 716 DMS Titrino.

Calculation:

mg/L CPCl = EP1 * C01 * C02 * C03 / C00 ; 1; ppm

EP1 = mL sodium dodecylsulfate consumed to reach the first equivalence pointC00 = sample volume in mL

C01 = 1.432 (conversion factor: 1 mL sodium dodecylsulfate 0.004 mol/L =1.432 mg CPCl)

C02 = 1000 (conversion factor for mg/L)C03 = 0.952 (titer)

Result: x(6) = 532.8 9.3 mg/L CPCl.


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Parameter report of the 716 DMS Titration curve and result block for the analysis of theTitrino. mouth wash solution.

Literature

R. Schulz, R. Gerhards,

Optimization of the potentiometric titration of ionic detergents,American Laboratory 26/11, (1994) 40-44 andInternational Laboratory 24/10, (1994) 10-14.

Schulz, R. Gerhards, H.-D. Kseborn,Die potentiometrische Bestimmung von Anionentensiden in Rinse-off-Produk-ten,SFW-Journal 120/13, (1994) 776-783.

R. Schulz, R. Gerhards,A new titrant for the potentiometric titration of anionic detergents,Tenside/Detergents, issue 1, 1995.

S. Selig,

The potentiometric titration of surfactants and soaps using ion-selective elec-trodes,Fresenius J. Anal. Chem. 300, (1980) 183-188.

G. C. Dilley,Determination of anionactive matter in detergents by potentiometric titration,Analyst 105, (1980) 713-719.

K. Kosswig, H. Stache,Die Tenside,Carl Hanser Verlag, Mchen/Wien, 1993, ISBN 3-446-16201-1.

Stache, K. Kosswig,Tensid-Taschenbuch, 3. Auflage,Carl Hanser Verlag, Mnchen/Wien, 1990, ISBN 3-446-15704-2.

M. Schmitt,Analysis of Surfactants, Surfactant Science Series Vol. 40,Marcel Dekker Inc., New York, 1992, ISBN 0-8247-8580-0.


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D. C. Cullum,Introduction to Surfactant Analysis,Blackie Academic & Professional, London, 1994, ISBN 0-7514-0025-4.

ASTM D 4251-89,

Standard Test Method for Active Matter in Anionic Surfactants by Potentiomet-ric Titration.

ASTM D 5070-90,Standard Test Method for Synthetic Quaternary Ammonium Salt in Fabric Sof-teners by Potentiometric Titration.

R. Schulz,Th. Goldschmidt AG, Zentralbereich Forschung/Analytik, Goldschmidtstrasse100, D-45127 Essen, Fax +49 201 173 19 97,Numerous personal communications regarding his work and lecture material.

R. Schulz, P. BruttelBestimmung ionischer Tenside in Mundpflegeprodukten

SFW-Journal 124/3, (1998) 138-146. R. Schulz, P. Bruttel

Analytik ionischer Tenside in HaarpflegeproduktenSFW-Journal 125/2, (1999) ........

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Titrimetric Potentiometric Determination of Anionic and Cationic Surfactants