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Synthesis and characterisation ofnovel chelating resin for selectivepreconcentration and tracedetermination of Pb(II) ions in aqueoussamples by innovative microsampleinjection system coupled flame atomicabsorption spectrometryAli N. Siyalab, Latif Elçia, Saima Q. Memonb, Abdullah Akdoğana,

Aysen Hola, Aslihan Arslan Kartala & Muhammad Yar Khuhawarb

a Chemistry Department, Faculty of Science and Art, PamukkaleUniversity, Denizli 20017, Turkeyb Institute of Advance Research Studies in Chemical Science,Faculty of Natural Science, University of Sindh, Jamshoro 76080,PakistanPublished online: 30 Jan 2014.

To cite this article: Ali N. Siyal, Latif Elçi, Saima Q. Memon, Abdullah Akdoğan, Aysen Hol,Aslihan Arslan Kartal & Muhammad Yar Khuhawar (2014) Synthesis and characterisation ofnovel chelating resin for selective preconcentration and trace determination of Pb(II) ions inaqueous samples by innovative microsample injection system coupled flame atomic absorptionspectrometry, International Journal of Environmental Analytical Chemistry, 94:8, 743-755, DOI:10.1080/03067319.2013.871716

To link to this article: http://dx.doi.org/10.1080/03067319.2013.871716

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Synthesis and characterisation of novel chelating resin for selectivepreconcentration and trace determination of Pb(II) ions in aqueous samples

by innovative microsample injection system coupled flame atomicabsorption spectrometry

Ali N. Siyala,b, Latif Elçia*, Saima Q. Memonb, Abdullah Akdogana, Aysen Hola, AslihanArslan Kartala and Muhammad Yar Khuhawarb

aChemistry Department, Faculty of Science and Art, Pamukkale University, Denizli 20017, Turkey;bInstitute of Advance Research Studies in Chemical Science, Faculty of Natural Science, University of

Sindh, Jamshoro 76080, Pakistan

(Received 4 May 2013; final version accepted 6 November 2013)

Expanded polystyrene (EPS) foam waste (white pollutant) was utilised for the synthesis ofnovel chelating resin i.e. EPS-N = N-α-Benzoin oxime (EPS-N = N-Box). The synthesisedresin was characterised by FT-IR spectroscopy, elemental analysis, and thermogravimetricanalysis. A selective method for the preconcentration of Pb(II) ions on EPS-N = N-Box resinpacked in mini-column was developed. The sorbed Pb(II) ions were eluted with 5.0 mL of2.0 mol L−1 HCl and determined by microsample injection system coupled flame atomicabsorption spectrometry (MIS-FAAS). The average recovery of Pb(II) ions was achieved95.5% at optimum parameters such as pH 7, resin amount 400 mg, flow rates 1.0 mL min−1

(of eluent) and3.0 mL min−1 (of sample solution). The total saturation capacity of the resin,limit of detection (LOD) and limit of quantification (LOQ) of Pb(II) ions were found to be30 mg g−1, 0.033 μg L−1 and 0.107 μg L−1, respectively with preconcentration factor of 300.The accuracy, selectivity and validation of the method was checked by analysis of sea water(BCR-403), wastewater (BCR-715) and Tibet soil (NCS DC-78302) as certified referencematerials (CRMs). The proposed method was applied successfully for the trace determinationof Pb(II) ions in aqueous samples.

Keywords: expanded polystyrene foam; chelating resin; lead; preconcentration; MIS-FAAS

1. Introduction

Lead is a non-essential heavy metal, recognised as potential toxin and carcinogen [1]. Thepermissible limit of Pb(II) ions in drinking water is 0.05 mg L−1. Exceeding this limit, it reactswith mercapto group and phosphate ions of enzymes, ligands and other biomolecules, andthereby inhibits the bio-synthesis of haeme units, affecting membrane permeability of kidney,liver and brain cells [2,3]. Therefore, the accurate and precise determinations of trace heavymetal ions in air, water, soil, plant, food, geological samples, etc. have been becoming a majorinterest of chemists [4,5]. Flame atomic absorption spectrometry (FAAS) has been widely usedfor determinations of metals because of its selectivity, low cost, and operational simplicity.However, the direct determinations of trace metal ions are limited owing to their lowerconcentrations than the LOD of FAAS and matrices interferences [6]. To solve this problem,preconcentration and separation of trace heavy metal ions from the matrices is recommended

*Corresponding author. Email: elci@pau.edu.tr

Intern. J. Environ. Anal. Chem., 2014Vol. 94, No. 8, 743–755, http://dx.doi.org/10.1080/03067319.2013.871716

© 2014 Taylor & Francis

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prior to their trace determinations [7]. Different techniques such as co-precipitation [8,9], ionexchange [10–12], solvent extraction [13,14] and solid phase extraction (SPE) [15,16] havebeen used for the preconcentration/separation of metal ions. Among these, SPE is the mostattractive technique for the preconcentration/separation of metal ions because of its advantagessuch as operational ease, recycling of solid phase, higher preconcentration factor and selectivity,lower consumption of solvents, lower cost and operation time, and environmental-friendlynature [17,18]. For SPE, various adsorbents such as activated carbon, silica gel, polyurethanefoam, microcrystalline naphthalene, Chelex-100, fullerene, alumina, and Amberlite XAD resinshave been reported [19]. The interest has been increasing in the development of chelating resinsfor trace metal ions preconcentration due their high degree of selectivity, versatility, durability,and high metal loading capacity [20]. For the synthesis of chelating resins, the chelating ligandsare coupled with polymeric matrix through –N = N–, –C = N– or –CH2– spacer [21].

In this study, EPS foam waste was utilised for the synthesis of EPS-N = N-Box resin bycoupling with α-benzoin oxime ligand. The resin was used for the preconcentration/separationof Pb(II) ions prior to its trace determination in aqueous samples by MIS-FAAS using 100 μL ofsample solution per determination.

2. Experimental

2.1 Apparatus

Determination of lead ions was performed by PerkinElmer flame atomic absorption spectro-meter (AAnalyst 200) equipped with lead hollow cathode lamp. The operating parameters wereset as recommended by the manufacturer (slit width, 0.7 nm; current, 10 mA and wavelength,283.3 nm). The flame composition was air (flow rate, 10 L min−1) and acetylene flame (flowrate, 2.5 L min−1). For the characterisation of synthesised resin, PerkinElmer FT-IR spectrometer(SN-92417, UK) was used to record FT-IR spectra, PerkinElmer Series II CHNSO Analyzer2400 was used for elemental analysis, thermogravimetric analyser (Shimadzu DTG-60H, Japan)was used for thermal gravimetric analysis (TGA) using aluminum pan with heating rate, 10°C min−1 under N2 atmosphere at flow rate of 100 mL min−1 and scanning electron microscope(SEM) (JSM-6490LV, JEOL, Japan) was used for the SEM analysis. Digital pH meter (Hanna211, Germany) equipped with a combined glass calomel electrode was used for pH measure-ments. PVC column with stopcock and frits (porosity 20 μm) was used for preconcentrationexperiments. The sample solutions were passed through the column by phenomenex vacuummanifold (JS, Selecta, SA, SN-0470174, Spain).

2.2 Reagents and solutions

Analytical reagent-grade chemicals were employed for the preparation of all solutions.Ultrapure quality water (resistivity 18.2 MΩ cm−1) obtained by reverse osmosis system(Human Corp., Seoul, Korea) was used throughout the experiments. The working and referencesolutions were prepared daily by dilution of commercial stock solution (1000 ± 4.0 mg L−1)of Pb(II) ions purchased from Fluka. HCl and NaOH solutions were used to adjust pH 2–6 and7–10, respectively. EPS foam was collected from Denizli, Turkey. CRMs such as sea water(BCR-403) and wastewater (BCR-715) were furnished by European Commission, JointResearch Centre, Institute for Reference Materials and Measurements (EC-JRC-IRMM), Geel,Belgium and Tibet soil (NCS DC-78302) was furnished by China National Analysis Center forIron and Steel.

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2.3 Samples collection

Polyethylene bottles were used for water samples storage. The bottles were successivelypre-cleaned with water, detergent, water, dilute nitric acid and water. The wastewatersamples were collected from industrial site areas in Denizli-Turkey and Karachi-Pakistan.The rain water samples were collected in Denizli-Turkey on 10 December 2012 at 9.10 AMand Karachi-Pakistan on 13 December 2012 at 6.20 AM. Sea water sample was collectedfrom Karachi-Pakistan. The flood water sample was collected from Sindh-Pakistan in July2010. All the samples were filtered through millipore cellulose nitrate membrane filter (poresize 45 µm) and acidified to pH 2 with 2.0 mol L−1 HNO3 and stored at 4°C for theanalysis. The tap water samples were collected from research laboratories, Department ofChemistry, Pamukkale University, Turkey and IARSCS, University of Sindh, Jamshoro-Pakistan. The bottled water (Nestle) was purchased from local market, Jamshoro-Pakistan.The bottled water (pirsu) and the soft drink (Zafer Gazoz) were purchased locally fromDenizli-Turkey.

2.4 Synthesis of novel chelating resin

Figure 1 illustrates the scheme for the synthesis of EPS foam based chelating resin. The EPSfoam is composed of 5.0% PS and 95.0% air [1]. The EPS foam was modified to diazoniumderivative (d) by reported procedure [22] as; 10 mL of concentrated HNO3 and 25 mL ofconcentrated H2SO4 were poured into 250 mL of round bottom flask contained 5.0 g of EPSfoam (a) and stirred for 1.0 h at 60°C. The reaction mixture was poured into an ice–watermixture and filtered off. The nitro derivative (b) was washed repeatedly with water until freefrom acid and reduced by refluxing with 40 g of SnCl2, 45 mL of 2.0 mol L−1 HCl and 50 mLof ethanol for 10 h at 90°C. The amino derivative (c) was filtered off, washed with water,2.0 mol L−1 NaOH and water until free from base. The amino derivative was diazotised bysuspending in 50 mL of 1.0 mol L−1 HCl solution at 0–5°C and 1.0 mol L−1 NaNO2 solutionwas added drop wise with stirring until the reaction mixture turned to permanent dark blue colorwith starch iodide paper. The diazonium derivative (d) was filtered off, washed with ice-coldwater and reacted with α-benzoin oxime ligand (9.7 g in 250 mL of methanol) at 0–5°C for24 h. The synthesised EPS-N = N-Box resin (e) was filtered off, washed, and air-dried. Theyield of product was found to be 76.5%.

N=N CH

OH

C

NOH

Nitro derivative Amino derivative Diazonium derivative

HNO3/H2SO4 SnCl2/HCl NaNO2/HCl

CH

OH

C

NOH

Chelating Resin

Expanded Polystyrene(EPS)

NO2 NH2 N2Cl

α-Benzoin oxime

α-Benzoin oxime

Figure 1. Reaction scheme for the synthesis of EPS-N = N-Box resin.

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2.5 Column preparation

The PVC column (170 mm × 80 mm) was packed with 400 mg of EPS-N = N-Box resin(grounded and sieved to 150–200 μm) and small amount of glass wool was placed at the bothends of the column to prevent the loss of the resin when the sample solution was passed throughthe column. The packed resin was washed successively with water, 1.0 mol L−1 HNO3, water,1.0 mol L−1 NaOH, water, 2.0 mol L−1 HCl and water to remove the contaminants. The columnwas preconditioned at desired pH before. After each of the uses, the resin packed in the columnwas washed thoroughly with water and then stored in water for reuse.

2.6 Combined preconcentration procedure

The proposed method was tested with model solution prior to the trace determination of Pb(II)ions in real samples. For this, 25 mL of model solution (2.0 mol L−1) of Pb(II) ions was adjustedto pH 7 and passed through the column at the flow rate of 3.0 mL min−1. The retained Pb(II)ions onto the resin packed in column were eluted with 5.0 mL of 2.0 mol L−1 HCl which wasfurther preconcentrated by evaporation on a hot plate at ~40 ºC to dryness. Thereafter, 0.5 mL of2.0 mol L−1 HCl was delivered into the residue (obtained after evaporation) and subjected toMIS-FAAS for Pb(II) ions determination using 100 µL of sample solution for single run. Thesampling rate of combined procedure was 3.0 samples h−1.

2.7 Analysis of certified reference materials

The method was validated by analysis of three CRMs. For this, 2.0 g of Tibet soil (NCS DC-78302) was digested with 20 mL of 2.0 mol L−1 HNO3, filtered, and diluted to 150 mL. A3.0 mL aliquot of wastewater (BCR-715) and 5.0 mL aliquot of sea water (BCR-403) werediluted to 150 mL as optimum sample volume was 150 mL for quantitative recovery andmaximum preconcentration factor of Pb(II) ions. The sample solutions were preconcentratedaccording to the proposed procedure and subjected to MIS-FAAS for the trace determination ofPb(II) ions in CRMs.

2.8. Microsample injection system coupled flame atomic absorption spectrometry(MIS-FAAS)

In routine, 2.0–4.0 mL of sample solution is required for single element determination byFAAS. Multi-element determinations require larger volume which lead lower preconcentrationfactor. Therefore, MIS-FAAS was employed to solve this problem. For this, nebuliser needle ofFAAS was coupled with the disposable tip of micropipette (capacity 20–200 µL) usingPolytetrafluoroethylene (PTFE) capillary tube (length of 10.0 cm). A micropipette was usedto inject 100 µL of sample solution and absorbance was recorded as peak height. TheMIS-FAAS offers 100 µL of sample solution for single determination with maximumabsorbance signal, high accuracy and reproducibility [23].

3. Results and discussion

3.1 Characterisation of chelating resin

3.1.1 FT-IR spectroscopy

Figure 2 shows the FT-IR spectrum of EPS (a) and EPS-N = N-Box resin (b), the characteristicadditional bands in spectrum (b) at 3312, 1700, 1480 and 1030 cm−1 are due to the stretching

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vibrations of O–H, N = N, C = N and C–O, respectively, indicated the successful coupling ofchelating ligand (α-benzoin oxime) with EPS through an azo spacer.

3.1.2 Elemental analysis

The synthesised resin was characterised by elemental analysis. The experimental values werefound to be; C, 74.35%; H, 5.72%; N, 11.29%, O; 8.64% whereas, the theoretical valuescalculated for single repeating unit of polymeric chelating resin (C23H21N3O2 ) are; C,74.37%; H, 5.70%; N, 11.31%, O; 8.62%. The results showed good correlation betweenexperimental and theoretical values which indicated the successful coupling of α-benzoinoxime with each of repeating units of EPS through an azo spacer.

3.1.3 Thermal gravimetric analysis

Figure 3 shows a thermogram of synthesised resin i.e. EPS-N = N-Box resin. The characteristicsingle step mass loss of 60.89% at the temperature range of 162.24–362.48°C (start–end)corresponds to the loss of α-benzoin oxime ligand. This mass loss correlates with the theoreticalmass loss (60.91%) of α-benzoin oxime ligand. The good correlation between experimental andtheoretical mass loss values confirmed the successful coupling of α-benzoin oxime with eachrepeating units of EPS through an azo spacer.

3.2 Effect of pH

The pH is an important parameter which influences the surface activity of the resin for theretention of Pb(II) ions. Thus, the effect of pH on the retention of Pb(II) ions was investigated.For this purpose, 25 mL of model solution (2.0 μg L−1) was adjusted to pH 2–10 and passedthrough the column at flow rate of 3.0 mL min−1. The recovery of Pb(II) ions was achieved95.3 ± 3.4% at pH 7 as shown in Figure 4. The reason behind this narrow pH range can be

Figure 2. FT-IR spectrum of EPS (a) and EPS-N = N-Box resin (b).

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explained on the basis of reaction of oxime functionality with Pb(II) ions. Lead exists indifferent.

Species at different pH such as Pb2+ > 80% at pH 7, Pb2+ ~50%, Pb(OH)+ ~45%, Pb3(OH)42+

~3.0%, and Pb(OH)2 ~1.0% at pH 8. In acidic medium, the H+ ions compete with Pb2+ ions so theretention of Pb(II) ions was increased with increase in pH 5–7 as number of H+ ions weredecreased. Further increase in pH 7–10, the retention of Pb(II) ions was decreased as lead startedto form hydroxides [1].

3.3 Effect of eluent solvent

The type and concentration of eluents are important factors which affect the reusability of theresin. Thus, effect of type, concentration and volume of eluents on the desorption of Pb(II) ionswas investigated. For this, 3–10 mL of 1–4 mol L−1 HCl and HNO3 were tested as eluentsolvents. The recovery of Pb(II) was achieved ≥ 95.5% with 5.0 mL of 2–3 mol L−1 HCl and5–10 mL of 4.0 mol L−1 HNO3 as shown in Table 1. Therefore, 5.0 mL of 2.0 mol L−1 HCl waschosen as best eluent for quantitative desorption of Pb(II) ions. Normally, high concentrated

Figure 4. Effect of sample solution’s pH on the recovery of Pb(II) ions (sample volume 25 mL, n = 3).

Figure 3. Thermogram of EPS-N = N-Box resin.

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acidic eluent are not recommended, therefore, nitric acid was not preferred because of its highconcentration and oxidising property which affected the life of the column.

3.4 Effect of flow rate

The flow rate of sample solution is related to the contact time between analytes and resin whichinfluences on the adsorption of analytes, whereas flow rate of eluent is related to the contacttime between analytes and eluent solvent which influences on the desorption of analytes. Thus,the effect of flow rate of eluent and sample solution on the recovery of Pb(II) ions wasinvestigated. For this, 25 mL of model solution was adjusted to pH 7 and passed through thecolumn at the flow rate of 2–8 mL min−1. The retained Pb(II) ions were eluted with 5.0 mL of2.0 mol L−1 HCl at the flow rate of 1–5 mL min−1. The flow rate was controlled by stopcockwith RSD ≤ 3.4% and relative error of ≤ −5.0%. The recovery of Pb(II) ions was achieved ≥95.0with RSD ≤ 2.0% at flow rate of 2–3 mL min−1 of sample solution and 1.0 mL min−1 of eluentas shown in Figure 5. Therefore, the optimum flow rate of sample solution and eluent werechosen as 3.0 and 1.0 mL min−1, respectively, for further experiments.

3.5 Effect of sample volume

The effect of sample volume on the recovery of Pb(II) ions was investigated. For this, 10 mL ofmodel solution (2.0 μg L−1) was prepared. The model solution was diluted up to 180 mL andpassed through the column at optimum conditions. The retained Pb(II) ions were eluted with5.0 mL of 2.0 mol L−1 HCl. The recovery of Pb(II) ions from the diluted solutions was achieved≥95.0% with RSD ≤ 2.0% until 150 mL of sample solution as shown in Figure 6. Thepreconcentration factor calculated was 300 for Pb(II) ions as sample volume (150 mL) isdivided by volume of sample solution (0.5 mL) subjected to MIS-FAAS.

Table 1. Effect of eluents on the recovery of Pb(II) ions (V = 25 mL, n = 3).

Types Conc. (mol L−1) V(mL) R ± SD (%)

HCl 0.5 5.0 80.1 ± 3.2HCl 1.0 5.0 84.8 ± 4.1HCl 1.5 5.0 90.3 ± 1.2HCl 2.0 5.0 95.5 ± 2.4HCl 3.0 5.0 95.9 ± 3.2HCl 3.0 4.0 90.1 ± 2.2HCl 2.0 4.5 90.4 ± 1.3HCl 2.0 4.0 82.2 ± 2.2HCl 2.0 3.0 68.1 ± 1.3HNO3 0.5 5.0 44.8 ± 4.3HNO3 1.0 5.0 69.7 ± 3.2HNO3 1.5 5.0 62.1 ± 2.0HNO3 2.0 5.0 67.1 ± 3.2HNO3 3.0 5.0 77.2 ± 2.4HNO3 3.0 10 80.1 ± 2.3HNO3 4.0 10 97.5 ± 3.5HNO3 4.0 5.0 96.0 ± 2.5

Conc.: Concentration of eluents, V: volume of eluents, R: Recovery, SD: Standard deviation.

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3.6 Effect of resin amount

For resin amount optimisation, the sample solution was passed through column packed with100–600 mg of the resin at optimum conditions. The recovery of Pb(II) ions was increased withincrease in resin amount 200–400 mg, became constant at 400–500 mg and declined at ≥500 mgas shown in Figure 7. Therefore, 400 mg was chosen as optimum resin amount for furtherexperiments.

3.7 Sorption capacity

The sorption capacity of PS-N = N-Box resin for Pb(II) ions was evaluated by column method.Breakthrough curve (Figure 8) was plotted to obtain the capacity. Breakthrough point occurswhen the effluent concentration (Cf) become 5.0% of the initial concentration (Co). The columnattains complete saturation when Cf approaches to Co [24]. The resin amount, flow rate(of sample solution) and the initial concentration of Pb(II) ions were fixed as; 400 mg,3.0 mL min−1 and 10 mg L−1, respectively. The total saturation capacity of the resin wasfound to be 30 mg g−1. The sorption capacity of the resin was also determined by batch methodand was found to be 32.5 mg g−1.

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30

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80

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100

0 1 2 3 4 5 6 7 8

Re

co

ve

ry

(%

)

Flow rate (mL min–1

)

Sample Solution

Eluent solution

Figure 5. Effect of flow rate of eluent and sample solution on the recovery of Pb(II) ions (sample volume25 mL, n = 3).

40

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60

70

80

90

100

110

0 20 40 60 80 100 120 140 160 180

Re

co

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(%

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Figure 6. Effect of sample volume on the recovery of Pb(II) ions (n = 3).

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3.8 Effect of matrix ions

The matrix ions affect the selectivity and sensitivity of analytical methods. Thus, the effect ofpossible matrices ions such as Na+, K

+, Mg2+, Ca2+, Ba2+, Cl−, F−, HCO3−, CO3

2−, SO42−, PO4

3−,NO3

− and CH3COO− on the recovery of Pb(II) ions was investigated. For this, 25 mL of model

solution containing matrix ions in different concentrations was passed through the column atoptimum conditions. The recovery of Pb(II) ions was achieved ≥95.1% with RSD ≤4.2% asshown in Table 2. The sorption and interference effect of metal ions such as Cr(III), Mn(II), Fe(II),Co(II), Ni(II) Cu(II), Zn(II) and Cd(II) was also investigated. The adsorptions of the metal ionswere found to be 50.3, 13.1, 50.2, 8.5, 47.6, 43.5, 9.3 and 38.0%, respectively. The recovery of Pb(II) ions was achieved 96–100% with RSD ≤ 3.5% in presence of the metal ions in the ratioof 1:10.

3.9 Analytical performance of the method

Analytical figures of merits of the proposed procedure were investigated for precision, accuracy,limit of detection (LOD), limit of quantification (LOQ) and resin stability. The precisionof the method was tested by multiple determinations (n = 7) of Pb(II) ions in the range of0.07–0.2 µg L−1 with RSD ≤ 5.0%.

40

50

60

70

80

90

100

100 200 300 400 500 600

Re

co

ve

ry

(%

)

Resin amount (mg)

Figure 7. Effect of resin amount on the recovery of Pb(II) ions (sample volume 25 mL, n = 3).

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 200 400 600 800 1000 1200 1400 1600

Cf/C

o

Volume (mL)

Figure 8. Breakthrough curve for total sorption capacity of EPS-N = N-Box resin for Pb(II) ions.

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The validation and accuracy of proposed method were evaluated by analysis of sea water(BCR-403), wastewater (BCR-715) and Tibet soil (NCS DC-78302) as CRMs. The recovery ofPb(II) ions from sea water (certified value 0.024 µg kg−1), wastewater (certified value490.0 µg mL−1), and Tibet soil (certified value 14.2 ± 2.7 µg g−1) were found to be 95.8%(found value 0.023 µg kg−1), 98.0% (found value 480 µg mL−1) and 95.1% (found value13.5.0 µg g−1), respectively with RSD ≤3.0% and relative error of ≤−4.9%. The results revealedthe good agreement between observed and certified values which showed validation and highaccuracy of the method with t-test at 95.0% confidence level. In order to further validate theproposed procedure, the spiking recovery test of Pb(II) ions was also performed. The recoveriesof Pb(II) ions from the real samples were achieved quantitative as shown in Table 3.

According to IUPAC, the limit of detection (LOD) and quantification (LOQ) are defined asblank + 3σ and blank + 10σ, respectively (where σ is standard deviation of blank analysis for 15replicates) [25,26]. The LOD and LOQ were found to be 0.033 and 0.107 μg L−1, respectivelyof Pb(II) ions. Before preconcentration the linear range of concentration was 0.5–20 mg L−1

with regression equation: y = 0.0155x + 0.0007 and R2 = 0.9991. Mean value for absorbance ofblank was 0.010203 with standard deviation of 0.04867. After preconcentration, the linear rangeof concentration was 0.00167–0.0667 mg L−1 with regression equation: y = 4.5863x + 0.0036and R2 = 0.9987. The experimental preconcentration factor calculated from slope ratio of thecalibration curves was ~296.

The resin was recycled more than 500 times, without significant loss in capacity andrecovery values which showed high stability and reproducibility of the resin.

3.10 Applications of the method

The optimised method was applied for the preconcentration of Pb(II) ions prior to its tracedetermination in different aqueous samples. The samples were analysed without standardaddition (by external calibration curve) and with standard addition of 5–20 µg of Pb(II) ionsin 150 mL of sample solution. The results are summarised in Table 3. The recoveries of Pb(II)

Table 2. Effect of matrix ions on the recovery of Pb(II) ions (Volume = 25 mL, n = 3).

Ions Added TLC (mg L−1) R ± SD (%)

Na+ NaNO3 10,000 95.6 ± 4.2K+ KCl 10,000 97.7 ± 1.7Mg2+ MgCl2 4000 96.6 ± 1.8Ca2+ CaCl2 4000 97.5 ± 1.8Ba2+ BaCO3 5000 97.8 ± 1.5Cl− NaCl 25,000 95.1 ± 1.1F− NaF 22,000 96.5 ± 2.5HCO3

− NaHCO3 1000 96.1 ± 1.8CO3

2− Na2CO3 1000 97.1 ± 1.1SO4

2− (NH4)2SO4 500 97.7 ± 2.8PO4

3− Na3PO4 10,000 98.7 ± 2.0NO3

− KNO3 18,000 96.6 ± 3.0CH3COO

− CH3COONa 16,000 96.5 ± 2.5M Soluble salts 1:10 96–99.8 (±1.5-3.0)

TLC: Tolerable concentration of matrix ions R: Recovery, SD: Standard deviation, M: Cr(III), Mn(II), Fe(II), Co(II), Ni(II) Cu(II), Zn(II) and Cd(II).

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ions from water samples were achieved quantitative except for the soft drink (86–90.5%) whichwas probably due to the sugar content.

3.11 Comparison with reported methods

Different methods have been reported for the preconcentration of Pb(II) ions in aqueous samplesusing Amberlite XAD based chelating resins [27–43]. In this method, EPS foam based EPS-N = N-Box resin was used for the preconcentration of Pb(II) ions prior to its trace determinationin aqueous samples by MIS-FAAS. The method parameters such as recovery, preconcentrationfactor and sorption capacity are comparatively better and LOD value is comparatively lowerthan the reported methods (Table 4). The most of the reported methods worked at pH other than7, whereas the proposed method worked at pH 7 which was comparatively easy to be adjusted.

4. Conclusion

EPS foam waste (white pollutant) based chelating resin i.e. EPS-N = N-Box resin was success-fully synthesised and characterised by FT-IR spectroscopy, elemental analysis and TGA. Anovel preconcentration method was developed for the trace determination of Pb(II) ions by

Table 3. Determinations of Pb(II) ions in spiked samples (sample volume = 150 mL, n = 3).

Sample-aAdded(µg)

Found(µg)

R ± SD(%) Sample-b

Added(µg)

Found(µg)

R ± SD(%)

Rain water 0.0 nd – Rain water 0.0 nd –5.0 5.8 96.0 ± 4.5 5.0 4.9 98.0 ± 3.010 9.8 98.0 ± 2.5 10 9.9 99.0 ± 3.520 19.8 99.0 ± 3.5 20 19.5 97.5 ± 2.5

Tap water 0.0 nd – Tap water 0.0 nd –5.0 4.9 98.0 ± 2.8 5.0 4.8 96.0 ± 3.510 9.6 96.0 ± 3.3 10 9.5 95.0 ± 2.120 18.9 94.5 ± 3.5 20 19.4 97.0 ± 1.9

Bottled water(Pirsu)

0.0 nd – Bottled water(Nestle)

0.0 nd –5.0 4.8 96.0 ± 6.6 5.0 4.9 98.0 ± 4.210 9.5 95.0 ± 3.3 10 9.6 96.0 ± 3.020 18.9 94.5 ± 1.6 20 19.6 98.0 ± 1.3

Wastewater-1 0.0 nd – Wastewater-1 0.0 11.4 –5.0 5.3 106.0 ± 6.6 5.0 16.8 108.0 ± 3.310 10.4 104.0 ± 1.9 10 22.1 107.0 ± 2.120 20.4 102.0 ± 2.5 20 32.6 106.0 ± 2.4

Wastewater-2 0.0 nd – Sea water 0.0 5.3 –5.0 5.2 104.0 ± 3.8 5.0 10.1 96.0 ± 2.010 10.6 106.0 ± 3.3 10 15.0 97.0 ± 2.520 20.4 102.0 ± 2.5 20 25.0 98.5 ± 2.5

Soft drink(ZaferGazoz)

0.0 nd – Flood water 0.0 nd –5.0 4.3 86.0 ± 6.6 5.0 4.8 96.0 ± 3.310 9.0 90.0 ± 3.3 10 9.8 98.0 ± 3.320 18.1 90.5 ± 1.0 20 19.7 98.5 ± 4.8

a: Samples were collected from Turkey, b: Samples were collected from Pakistan, R: Recovery, SD: Standard deviation,nd: Not detected.

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MIS-FAAS using 100 µL of sample solution for single run. The analytical performance of themethod was evaluated by analysis of three CRMs and spiked water samples and proved to beaccurate, selective, and reproducible. The effect of matrix ions was studied, the results revealedthat the developed method possess high tolerance limit of matrices ions. The proposed methodwas applied for the selective preconcentration of Pb(II) ions prior to its trace determination inaqueous samples. The quantitative recovery of Pb(II) ions from sea water also confirmed theselectivity of the method. The capacity of the resin for Pb(II) ions is comparatively better thanAmberlite XAD based chelating resins. This method offers the substitution of Amberlite XADseries based resins with low cost EPS-N = N-α-Box resin.

AcknowledgementsThe authors would like to thank the Scientific and Technical Research Council of Turkey (TUBITAK) andDepartment of Chemistry, Pamukkale University, Turkey for providing financial supports and Laboratoryspace, respectively for present study.

References[1] S.Q. Memon, S.M. Hasany, M.I. Bhanger and M.Y. Khuhawar, J. Colloid Interf. Sci. 291, 84 (2005).[2] V. Singh, S. Tiwari, A.K. Sharma and R. Sanghi, J. Colloid Interf. Sci. 316, 224 (2007).

Table 4. Comparative Methods’ parameters for the preconcentration of Pb(II) ions prior to its tracedetermination by FAAS.

Chelating Resins Matrix Eluent CP PF R LOD pH Ref.

X-2-N2-PV water 3-4 M HNO3/HCl 0.62 23 98 40 3 [27]X-2-N2-oAP water 4 M HNO3 3.32 40 99 25.0 5-6 [28]X-2-N2-QZ water 4 M HNO3 5.28 50 91 15.0 5-7 [29]X-2-N2-CA water 1-4 M HNO3 38.6 200 97 4.06 3-8 [30]X-2-N2-PC water 1 M HNO3 21.7 100 94 3.80 5-7.5 [30]X-2-N2-TSA water 0.5-2 M HNO3 18.5 100 93 4.87 4 [30]X-2-N2-PG water 4 M HNO3/HCl 6.71 25 90 25 5.5-6.5 [31]X-2-Pox water 2 M HNO3 4.97 50 97 12.0 5-8 [32]X-2-N2-SA water 1 M HCl & Mix* 0.46 140 100 7.0 5 [33]X-4-N2-SAS water 0.5 M HNO3 78.1 50 97 0.15 4 [34]X-4-N2-ARS water 3-4 M HNO3 0.31 40 97 – 6 [35]X-4-N2-oABA water 1 M HNO3 12.4 400 103 2.5 6 [36]SP70-α-Box water 1 M HNO3 – 75 >95 16.0 5-9 [37]X-16-N2-San water, s* 4 M HCl 26.0 260 ≥ 97 1.17 6 [38]X-4-N2-oVEDA water 0.5 M HCl 7.8 200 >95 1.63 5-6 [39]X-2-N2-CB water, s** 0.5 M HNO3 40.2 10 100 – 6 [40]X-1180-N2-TAN water 2 M HNO3 – 200 >99 1.1 8.5 [41]X-4-N2-PAN water 0.5 M H2SO4 6.94 320 98 1.1 9.2 [42]X-4-N2-oHBAM water, s*** 2 M HCl 16.6 320 >98 1.1 4 [43]EPS-N2-α-Box water 2 M HCl 30 300 95.5 0.033 7 This work

CP: Capacity (mg g-1), LOD: Limit of detection (µg L-1), R: Average recovery (%), PF: Preconcentration factor, X:Amberlite XAD, Mix*: 3–4 M HNO3/2-4 M HCl mixture, M: mol L-1, s*: Biological samples, s**: plasma sample,s***: Fish, Urine and Multi-vitamin tablet samples, PV: Pyrocatechol Violet, oAP: o-Aminophenol, QZ: Quinalizarin,CA: Chromotropic acid, PC: Pyrocatechol, TSA: Thiosalicylic acid, PG: Pyrogallol, Pox: 5-Palmitoyl-8-hydroxyquino-line, SA: Salicylic acid, SAS: Salicylic aspartide, ARS: Alizarin Red-S, oABA: o-Aminobenzoic acid, San:Salicylanilide, oVEDA: N,N′-Bis(o-vanillinidene)ethylenediamine, CB: Calcein blue, TAN: 1-(2-Thiazolylazo)-2-naphthol, PAN: 1-(2-Pyridylazo)-2-naphthol, oHBAM: oHBAM: o-Hydroxybenzamide, EPS: Expanded polystyrene.Box: α-Benzoin oxime.

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