Solid phase extraction and determination of Cr(III)by spectrophotometry using cefaclor as a complexing reagentand FAAS

Lutfullah & Farheen Khan & Nafisur Rahman

Received: 16 May 2012 /Accepted: 24 September 2012# Springer Science+Business Media Dordrecht 2012

Abstract The present study reports on the application ofmodified groundnut shell as a new, easily prepared, andstable sorbent for the extraction of trace amount of Cr(III)in aqueous solution. 2-Hydroxybenzaldiminoglycine wasimmobilized on groundnut shells in alkaline medium andthen used as a solid phase for the column preconcentra-tion of Cr(III). The elution was carried out with 3 mL of2 molL−1 HCl. The amount of eluted Cr(III) was deter-mined by spectrophotometry using cefaclor as a com-plexing reagent and by flame atomic absorptionspectrometry (FAAS). Different experimental variablessuch as pH, amount of solid sorbent, volume and con-centration of eluent, sample and eluent flow rate, andinterference of other metal ions on the retention of Cr(III) were studied. Under the optimized conditions, thecalibration curves were found to be linear over the con-centration range of 13–104 and 10–75 μgL−1 with adetection limit of 3.64 and 1.24 μgL−1 for spectrophoto-metric method and FAAS, respectively. An enrichmentfactor of 200 and RSD of ±1.19–1.49 % for five succes-sive determinations of 25 μgL−1 were achieved. Thecolumn preconcentration was successfully applied tothe analysis of tap water and underground water samples.

Keywords Cefaclor . Chromium(III) . 2-Hydroxybenzaldiminoglycine (HBIG)-loaded

groundnut shell extractor . Spectrophotometry . Flameatomic absorption spectrophotometry

Introduction

Chromium is a metal which exists in different oxida-tion states ranging from +2 to +6. The most commonoxidation states, i.e., Cr(III) and Cr(VI), are of practi-cal importance with regard to environmental protec-tion. It is released to the environment from differentsources because it is widely used in the manufacturingprocesses such as tanning, steel works, plating, corro-sion control, chromate and chrome pigment produc-tion, etc. (Kumar and Riyazuddin 2009; Dogutan et al.2003; Papassiopi et al. 2009; Wang et al. 2010). Cr(III)is an essential trace element for maintaining glucose,cholesterol, fatty acid, and protein metabolism (Lian etal. 2005) and having great affinity for binding to DNAin an aqueous solution (Brien et al. 2001; Arakawa etal. 2000; Levina et al. 2001). As the concentration ofCr(III) in real samples is very low, suitable enrichmentprocedures are required for determination. Hence, pre-concentration and determination of Cr(III) from aque-ous samples have received considerable importance inenvironmental evaluation and protection in recentyears (Narin et al. 2007). Many instrumental techni-ques such as graphite furnace atomic absorption spec-trometry (Souza and Oliveira 2010), flame atomicabsorption spectrometry (FAAS) (Lopez-Garcia et al.2002), inductively coupled plasma–atomic emission

Environ Monit AssessDOI 10.1007/s10661-012-2917-1

Lutfullah (*) : F. Khan :N. RahmanDepartment of Chemistry, Aligarh Muslim University,Aligarh 202002 Uttar Pradesh, Indiae-mail: lutfullah05@gmail.com

L. (*) I F. Khan I N. Rahman

spectroscopy (Vellaichamy and Palanivelu 2010), X-ray fluorescence spectrometry (Aranda et al. 2010),gas chromatography with flame photometric detection(Ding et al. 2005), inductively coupled plasma–massspectrometry (Yu et al. 2001), and neutron activationanalysis (Miura et al. 2009) have been utilized fordetermination of chromium.

Several spectrophotometric methods have also beendeveloped for the determination of chromium basedon its reaction with reagents such as p-aminophenol(Veena and Narayana 2008), leuco xylene cyanol FF(Revanasiddappa and Kumar 2003), trifluoperazinehydrochloride (Revanasiddappa and Kumar 2002),saccharin (Cherian and Narayana 2005), variamineblue (Narayana and Cherian 2005), prochlorperazinedimaleate (Dayananda and Revanasiddappa 2007),cyclam (Mohammed 2005), 1,4-diaminoanthroqui-none (Hosseini and Asadi 2009), 1,5-diphenylcarba-zide (Jankiewicz and Ptaszynski 2005), and 2-hydroxybenzaldiminoglycine (HBIG) (Kumar andMuthuselvi 2006). FAAS and spectrophotometricmethods have been employed for the determinationof metal ions, but these methods are not suitable forthe determination at trace level owing to insufficientselectivity and sensitivity. Therefore, preconcentrationof trace elements from the matrix is usually necessaryto improve their detection and determination. Solidphase extraction (SPE) is an important technique tosolve such problems. The advantages associated withSPE are the following:

1. Simple preparation of solid phase2. Reusability of solid phase3. High preconcentration factor4. Rapid phase separation5. Simple to operate

The search for new adsorbents is an important factorfor improving analytical parameters such as selectivity,affinity, and capacity in SPE technique (Parham et al.2009). Various solid phases have been used for theextraction of trace heavy metals in environmental sam-ples prior to their instrumental analysis (Ghaedi et al.2007; Chandra et al. 2006; Tuzen et al. 2006; KalebasiAktas 2005; Lian et al. 2006; Narin et al. 2007; Jain etal. 2006). Moreover, naturally occurring materials canbe used as sorbent. They can be modified according tothe need. Cost is also an important factor for comparingthe sorbent materials. In general, low cost adsorbent isone which requires little processing, abundant in nature,

or a by-product or waste material from another industry.Attempt has been made to explore low cost adsorbentfor solid phase extraction of Cr(III).

In this manuscript, the solid phase extraction of Cr(III) on groundnut shells loaded with HBIG has beenreported. The effects of various experimental parameterssuch as pH, sample volume, volume of eluent, mass ofadsorbent, flow rate of sample and eluent, and interfer-ences of foreign ions have been studied. The spectro-photometric method was developed based on thereaction of Cr(III) with cefaclor at pH 4. Various param-eters affecting the formation of the complex have beenstudied. The developed method has been utilized for thedetermination of Cr(III) in water samples.

Experimental

Apparatus

Absorbance was measured on a Spectronic 20D+ spec-trophotometer (Milton Roy, USA) using matched glasscells. An atomic absorption spectrometer with an air–acetylene burner was used to determine the concentrationof Cr(III) (Model 932 Plus, GBC, Victoria, Australia).Measurement of pH of the solutions was done usingElico model Li-10 pH meter. A PerkinElmer FTIR1650 spectrophotometer was employed to record infraredspectra using the KBr pellet technique.

Materials and methods

All chemicals and reagents used were of analyticalreagent grade:

& A 1.0×10−2molL−1 chromium chloride hexahydratesolution (CAS 7791-20-0, Fluka Chemie AG,Darmstadt, Germany) was prepared in distilled water.

& A 1.35×10−2molL−1 cefaclor (CAS 53994-73-3,MW 367.808 gmol−1, Merck, USA) was preparedin distilled water.

& Buffer solutions such as sodium acetate–HCl (pH1.42–5.20) and boric acid–borax (pH 6.8–9.1) wereprepared.

Preparation of HBIG

The reagent HBIG was synthesized using the methodreported in the literature (Kumar and Muthuselvi

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2006). Aqueous solution of glycine (0.01 molL−1) wasmixed with potassium hydroxide (0.56 g/50 mL) andstirred for about 1 h on a water bath (50–60 °C) until aclear solution is obtained. To this solution, 1.22 gsalicylaldehyde dissolved in ethanol (20 mL) wasadded and the mixture was again heated on a waterbath (50–60 °C) for about 2–3 h until a clear solutionwas obtained. The resulting solution was used as areagent, and the structure of HBIG is shown in Fig. 1.

Preparation of adsorbent

Locally procured groundnut shells (100 mesh size) weretreated with 1 molL−1 HCl with stirring for 6 h to removedust particles. It was washed with hot distilled water anddried in an oven at 80 °C; 10 g of dried groundnut shellswas added to the solution of HBIG at room temperatureand stirred for 6 h. Finally, the material was filtered,washed with hot distilled water, and dried.

Spectrophotometric procedure

The column (1×10 cm) was packed with 0.5 g HBIG-loaded groundnut shells and conditioned with 5 mL buff-er solution at pH 7.5. The standard or sample solution(600 mL) containing Cr(III) adjusted to pH 7.5 waspassed through the column at a flow rate of 4.0 mLmin−1. After the enrichment, the column was washedwith distilled water and retained Cr(III) was eluted with3 mL of 2 molL−1 HCl. The resulting solution is evapo-rated to dryness, and the residue was dissolved in distilledwater and transferred to a 5-mL volumetric flask. Then,1.8 mL of 1.35×10−2molL−1 cefaclor and 1.5 mL of pH4.0 buffer solution were added to each flask and diluted tovolume with distilled water. The contents of each flask

were mixed well and heated on water bath (100±1 °C)for 3 min. The absorbance was measured at 360 nmagainst the reagent blank prepared similarly. The concen-tration of Cr(III) was obtained either from the calibrationcurve or corresponding regression equation.

FAAS procedure

The standard or sample solution (600mL) containing Cr(III) adjusted to pH 7.5 was passed through the columnpacked with 0.5 g HBIG-loaded groundnut shell at aflow rate of 4 mLmin−1. At the end of enrichment, thecolumn was washed with distilled water and retained Cr(III) was eluted with 3 mL of 2 molL−1 HCl. Theconcentration of Cr(III) was determined by FAAS.

Samples

Chromium(III) was determined in water samplesobtained from different origins such as tap water andunderground water. Before being used, samples werefiltered through a cellulose membrane of 0.45 μm.

Results and discussion

The absorption spectrum of Cr(III)–cefaclor complexwas recorded against a reagent blank. Similarly, ab-sorption spectrum of cefaclor was recorded against thesolvent blank. The absorption spectra are shown inFig. 2. It is evident from Fig. 2 that the Cr(III)–

Fig. 1 2-Hydroxybenzaldiminoglycine (HBIG)

180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 5200.0

0.1

0.2

0.3

0.4

0.5

0.6

(b)

(a)

Ab

sorb

ance

Wavelength(nm)

Fig. 2 Absorption spectra of (a) cefaclor and (b) Cr(III)–cefa-clor complex

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cefaclor complex and cefaclor exhibited absorptionmaxima at 360 and 260 nm, respectively. Job’s meth-od of continuous variations was employed to elucidatethe composition of the complex. Equimolar solution ofCr(III) and cefaclor was used to determine the metal toligand ratio. A plot was drawn between the absorbanceand mole fraction of Cr(III) (Fig. 3) which indicated1:1 (Cr(III)/cefaclor) stoichiometry in the complex.

The apparent formation constant, Kf, of the com-plex was calculated using the following expression:

Kf ¼AobsAextp

� �C

CM � AobsAextp

� �C

h iCL � Aobs

Aextp

� �C

h i

where Aobs and Aextp are the observed and extrapolatedabsorbance values for the complex, respectively. CM andCL are the initial concentration of Cr(III) and cefaclor in

moles per liter, respectively. C is the limiting concentra-tion. Thus, Kf for the complex is found to be 2.72×104.TheGibb’s free energy change (ΔG°) was also calculatedand found to be −10.98 KJmol−1. On the basis of exper-imental findings and literature background (Sultana et al.2003), the reaction mechanism is proposed (Fig. 4).

Optimization

Spectrophotometric method

Effect of heating time

The reaction of Cr(III) with cefaclor at pH 4.0 occursat 100±1 °C. Hence, the mixture was heated on a

water bath (100±1 °C) at different time intervals; theabsorbance at each time interval was measured. It wasobserved that a 2-min heating was sufficient to give amaximum absorbance. Therefore, a 3-min heatingtime was chosen for further studies.

Effect of pH

The effect of pH on the formation of the complex wasstudied in the range of 1.4–6.5. The maximum andconstant absorbance was found in the pH range of 3.5–4.5 (Fig. 5). Therefore, the pH of the solution wasmaintained at 4.0 in all subsequent measurements. Theinfluence of volume of the pH 4.0 buffer solution wasalso examined. It was found that the highest absor-bance was obtained with 1.0 mL of buffer solution(Fig. 6). Thus, a volume of 1.5 mL of pH 4.0 buffersolution was used in subsequent measurements.

Effect of the concentration of cefaclor

The effect of the volume of 1.35×10−2molL−1 cefa-clor on the absorbance of the complex was studied inthe range of 0.2–2.0 mL, keeping the concentration ofCr(III) constant (26 μgmL−1). It was observed that themaximum and constant absorbance was obtained inthe range of 1.4–2.0 mL of the reagent (Fig. 7). Thus,1.8 mL of cefaclor was taken as the optimum volumefor further studies.

Solid phase extraction

Effect of pH

The acidity of aqueous phase is one of the mostimportant parameters to be examined on the sorptionof metal ions on the complexing reagent-loaded solidsorbent. The effect of pH on the retention of Cr(III) onHBIG-loaded groundnut shells column was carried outover a wide pH range (2.0–8.5). For obtaining opti-mum pH, model solutions (50 mL) containing 20 μgCr(III) adjusted to a pH value lying in the range of2.0–8.5 were passed through the column. The retainedCr(III) on the column was stripped with 3 mL of 2 molL−1 HCl and determined by FAAS. The experimentwas performed in triplicate at each pH value. Theresults are shown in Fig. 8. The quantitative recoverieswere found at pH 7.5. So pH 7.5 was selected as theoptimum for subsequent measurements.

Mole fraction of Cr (III)

0.0 0.2 0.4 0.6 0.8 1.0

Abs

orba

nce

0.2

0.4

0.6

0.8

1.0

1.2

Fig. 3 Job’s plot to establish the stoichiometry of the Cr(III)–cefaclor complex [Cr(III)]0[cefaclor]01.35×10−2molL−1

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Effect of sample volume

Optimization of sample volume is one of the importantparameters in such studies. Hence, the effect of samplevolume on recovery values was examined on theHBIG-loaded groundnut shells column at 4.0 mLmin−1 flow rate. For this, sample solutions of 50,100, 200, 400, 600, 700, 800, and 900 mL containing20 μgL−1 of Cr(III) were passed through the column.The sorbed Cr(III) was eluted and determined byFAAS. It was found that the dilution effect was notsignificant for the sample volumes up to 600 mL. Athigher volumes, recoveries decreased. Since the elu-tion volume was 3 mL, an enrichment factor of 200was obtained.

Effect of eluent volume on recovery

Conditions were optimized to obtain a maximum re-covery of Cr(III). For this, 1.5–5.0 mL of 2.0 molL−1

HCl solutions was tested to desorb the retained Cr(III)

from the HBIG-loaded groundnut shells. It was foundthat 3 mL of 2 molL−1 HCl was sufficient for maxi-mum recovery (Fig. 9). Thus, 3 mL of 2 molL−1 HClwas used for complete desorption of Cr(III).

Effect of amount of adsorbent

The effect of the amount of adsorbent on the sorptionof Cr(III) at optimum pH was investigated in the rangeof 200–600 mg. The results showed that the optimumamount of adsorbent was found in the range of 400 to600 mg for maximum extraction of Cr(III). Hence,500 mg of adsorbent was used for quantitative extrac-tion and recovery of Cr(III) from water samples.

Effect of foreign ions

A systematic study of the effect of potentially interfer-ing species on the recovery of Cr(III) was undertaken.The preconcentration method was applied for 600 mLof model solution containing 50 μgL−1 of Cr(III)

Fig. 4 Reaction of Cr(III) with cefaclor

1 2 3 4 5 6 70.25

0.30

0.35

0.40

0.45

0.50

0.55

0.60

Abs

orba

nce

pH

Fig. 5 Effect of pH on the absorbance of the complex

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.20.25

0.30

0.35

0.40

0.45

0.50

0.55

0.60

Abs

orba

nce

Volume of buffer solution / mL

Fig. 6 Effect of the volume of a pH 4 buffer solution

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adjusted to optimum pH and different amounts offoreign ions. The criterion for interference of each ionswas set at ±5 % in the analytical signal obtained for asolution containing Cr(III) without any interferingions. The results are reported in Table 1. As can beseen in Table 1, the most common ions do not interferewith the proposed method.

Analytical performance

Analytical figures of merit were evaluated for thedetermination of Cr(III) according to the proposed

procedures at optimum conditions. The linear rangeof calibration graph was found to be 2.6–26.0 μgmL−1

with a molar absorptivity of 1.14×103Lmol−1cm−1

when direct spectrophotometric method was employed.Another calibration graph was also constructed afterpreconcentration which indicated a linear range of 13–104 μgL−1, taking 600 mL of solution to a final volumeof 3 mL of 2 molL−1 HCl.

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.20.0

0.1

0.2

0.3

0.4

0.5

0.6

Abs

orba

nce

Volume of 1.35 x 10-2 mol L-1 cefaclor / (mL)

Fig. 7 Effect of the volume of 1.35×10−2molL−1 cefaclor onthe absorbance of the complex

1 2 3 4 5 6 7 8 9

20

40

60

80

100

Rec

over

y (%

)

pH

Fig. 8 The influence of pH on the recovery of Cr(III) withHBIG-loaded groundnut shells

1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.255

60

65

70

75

80

85

90

95

100

Rec

over

y (%

)

Final volume /(mL)

Fig. 9 Effect of the final volume of the eluent (2 molL−1 HCl)on the recovery

Table 1 Effect of foreign ions on the preconcentration anddetermination of Cr(III) (50 μgL−1)

Ion Concentration (mgL−1) Recovery (%)

Na+ 1000 98.6

K+ 1000 98.6

Ca2+ 350 98.5

Mg2+ 350 98.7

Ba2+ 100 98.6

Sr2+ 100 98.7

Mn2+ 150 98.7

Co2+ 100 98.5

Cu2+ 40 98.6

Ni2+ 350 98.5

Zn2+ 350 99.0

Cd2+ 100 98.4

Pb2+ 100 98.3

Fe3+ 1 98.2

Hg2+ 150 98.6

Bi3+ 150 98.7

Al3+ 40 98.4

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On the other hand, the calibration curve showed a linearrange over the concentration range of 2–15 μgmL−1 usingdirect FAAS at 357.9 nm; 600 mL of standard solutionswas passed through the adsorbent column and eluted in3 mL of 2 molL−1 HCl.

For this calibration curve, a linearity over the concen-tration range of 10–75 μgL−1 was shown. Regressionanalysis of calibration data yielded the followingequations:

A ¼ �0:00134þ 0:00428C R2 ¼ 0:99967;

for 13–104 μgL−1 by preconcentration—spectro-photometry, and

A ¼ �0:00171þ 0:00913C R2 ¼ 0:99989;

for 10–75 μgL−1 by preconcentration—FAAS.The detection limits after preconcentration were

found to be 3.64 and 1.24 μgL−1 for spectrophotomet-ric method and FAAS, respectively. Precision of themethod was evaluated for 600 mL of 25 μgL−1 Cr(III)

sample. The preconcentration procedure was re-peated for ten times and determined by spectro-photometry (five times) and FAAS (five times).The results are reported in Table 2. The valuesof relative standard deviation (in percent) and re-coveries were found in the range of 1.19−1.49 and98.04–98.52 %, respectively.

Applications

The optimized preconcentration method was appliedto the determination of Cr(III) in various water sam-ples taken from different origins. A volume of 600 mLof water samples adjusted to the optimum pH waspassed through the column. The concentration of elut-ed Cr(III) was determined by the proposed spectro-photometric method and FAAS. The results arereported in Table 3. The results obtained by spectro-photometric method are in a good agreement withthose obtained by FAAS.

Conclusion

The study deals with the preparation and use of HBIG-loaded groundnut shells as a solid adsorbent for theseparation and preconcentration of trace amount of Cr(III). The immobilization of HBIG on groundnut shellsis simple. Under the optimum conditions, a precon-centration factor of 200 was achieved and, hence, theprocedure offers a rapid and reliable enrichment tech-nique for preconcentration and determination of tracelevel of Cr(III) in various water samples. The precisionbased on replicate analysis is less than ±2.0 %. Theresults demonstrate that other type of samples contain-ing Cr(III) can also be analyzed by the proposedprocedure.

Table 2 Test of precision

Concentration of Cr(III) (μgL−1)

Taken Found byFAAS method

Found by spectrophotometricmethod

25.0 24.38 24.05

25.0 24.75 24.20

25.0 24.90 24.62

25.0 24.85 24.82

25.0 24.25 24.85

X ¼ 24:63 X ¼ 24:51

Recovery (%)098.52 Recovery (%)098.04

RSD (%)01.19 RSD (%)01.49

Table 3 Determination of Cr(III) in water samples

Sample Cr(III) added(μgL−1)

Cr(III) found (μgL−1) byspectrophotometric method

Recovery (%) Cr(III) found(μgL−1) by FAAS

Recovery (%)

Tap water 0.0 ND – ND –

15.0 15.20 (1.80) 101.30 15.28 (1.2) 101.86

20.0 20.25 (1.6) 101.25 20.32 (1.1) 101.60

Underground water 0.0 18.10 (2.1) – 18.25 (1.3) –

10 27.85 (1.9) 98.60 27.90 (1.4) 98.08

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