SIMULTANEOUS DETERMINATION OF ZINC, CADMIUM, LEAD AND COPPER IN WATER BY POTENTIOMETRIC STRIPPING ANALYSIS

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1 Pak. J. Agri. Sci. 27 (2) 156, 199 SIMULTANOUS DTRMINATION OF ZINC, CADMIUM, LAD AND COPPR IN WATR BY POTNTIOMTRIC STRIPPING ANALYSIS Abdus Sattar, B. Ahmad & M. Jamshaid Nuclear Institute for Food and Agriculture, Peshaar & Department of Pharmacy, University of Punjab, Lahore Analysis of zinc (In) dmium (Cd), lead (Pb) and copper (Cu) in drinking and irrigation aters by potentiometric stripping analysis (PSA) is described. The ph and C of aters ere also determined. The results for zinc and copper ere compared ith those obtained by atomic absorption spectrophotometry (AAS) hich indited a signifintly (P<.1) strong correlation (r =.994 and.984 for In and Cu). The aters idely varied in ph, C, In, Cd, Pb and Cu contents. The range values observed ere; ph ( ), C ( urnhos crrr" x1), In ( ppb), Cd ( ppb), Pb ( ppb) and Cu ( ppb). Water of river-kabul contained generally higher levels of heavy metals and loer C than others. Loest Pb as in the tubeell ater at Noshera. INTRODUCTION The determination of heavy metals in foods, and drinking and irrigation aters has become an important part of most studies concerned ith environmental pollution and occupational health hazards. Although it is difficult to classify trace metals into essential and toxic groups, yet it is ell knon thatan essential metal becomes toxic at sufficiently high intakes (Khurshid and Qureshi, 1984). Heavy metals san be determined by several techniques such as neutron activation analysis, atomic absorption spectroscopy (AAS), anodic stripping voltammetry and potentiometric stripping analysis (Jagner, 1979; Qureshi et al., 1984; Satzger et al., 1984 and Benzo et al., 1984). Potentiometric stripping analysis (PSA) is an electrochemil approach for the assay of trace metals (Jagner and Graneli, 1976). It appears to be idely applible as stripping voltammetry and differential pulse stripping voltammetry (Jagner and Westerlund, 198). PSA is particularly ell suited in liquid samples since normally no pretreatment Of such samples is necessary unlike biologil materials here organic material must be destroyed prior to determination by any technique (Sattar et al., 1989). High correlations beteen atomic absorption spectrophotometry (AAS) and PSA technique forthe analysis of heavy metals in biologil materials and sea ater have already been described (Jagner and Aren, 1979). The objective of this study as to determine concentration of Cd, Pb, Cu and In in some drinking and irrigation aters available around Peshaer using the PSA. MATRIAL,S AND MTHODS Sampling: The drinking and irrigation aters ere collected thrice at eek interval and pooled. The samples ere acidified ith HClto.1 M immediately after sampling and stored in polyethylene flasks. Chemils: All chemils used, except mercury (II) nitrate ere of suprapure (merck) grade. The 1 ppm mercury (II) nitrate solution contained less than.2 Ilg L- 1 of In, Cd, Pb and Cu. Analytil procedures: Simultaneous determination of dmium, copper, lead and zinc as rried out by the potentiometric stripping technique (Danielsson et al., 1983) using the TetorStriptec system comprising glassy rbon electrode, saturated lomel electrode (SC) and platinum ire

2 - as counter electrode. To 5 ml of the acidified sea ater sample, mercury (II) ions ere added to give a total concentration of 2-4 mg L-1. The sample as placed in the analyser, the stirrer started and a stream of N passed through the sample at a rate of 2 about 2ml min.- 1.The analytil signal for each element is taken as the interval of time beteen to consecutive equivalence points on the time - potential curve (Fig. 1). The stripping curves ere measured at potential _ 1.1 volt vs SC and 18 seconds plating time for Cd, Cu and Pb hile volt vs SC and 18 seconds plating time for Zn. The concentration of the metal in the samples as evaluated by means of the standard addition technique; the 1-min preelectrolysis/stripping cycle being repeated after each addition. In comparison to libration curves, the standard addition method is considered to be appropriate especially hen the samples are of varying type and origin. In most experiments, to standard additions ere used and the concentration of the standard addition solution as chosen so that the first addition almost doubled the concentration of the analyte. The stripping time for the element considered as prolonged in proportion to the added amount. Then the unknon content in the acid digest and finally the sample as determined by simple lculations. Details of the methodology are available elsehere (Jagner, 1978; Lagner and Aren, 1979). The assays for Zn and Cu ere also made! by the atomic absorption spectrophotometry using Hitachi model 17-1 atomic absorption spectrophotometer for comparison of results. The ater samples ere also analysed for ph and C (USSLS, 1954). RSULTS AND DISSCUSSION The accuracy of the method as initially estimsted by comparison ith the results from the analysis of 16 samples of different concentrations. Closeness of the relation beteen these to methodologies measured by the linear correlation and regression. The correlation coefficients and regression equations of the data ere measured. The test statistics indited presence of a strong correlation for Zn and Cu beteen these to analytil techniques. The relationship as expressed by signifint linear (P <.5) regression of the forms: y = X for Zn (r =.994) Y = X for Cu (r =.984) here X as the amount of AAS analysis and Y as that of PSA. The results obtained by both of the methods ere almost similar. It as beuse the determinations ere made on standard samples, similar observations have been made for heavy metals such as Zn, Cd and Cu except Pb for hich signifintly higher values by PSA than AAS analysis ere found (Jagner and Aren, 1979). Tl,i;,e ide differences in sea-ater ere considered to be the result of contamination on board analysis. The characteristics and heavy metal contents of different aters are presented in Table 1. The analysis of distilled ater as also conducted for comparison, hich of course exhibited loer ph, C and contents of different heavy metals. The reason for unexpectedly higher amounts of zinc in the distilled ater is not clear. It may perhaps be the result of some contamination from the distillery. The ph of these aters ranged and the C as found to vary beteen and 16.6mhoscm-1 x 1. The highest C as in the tube-ell ater obtained from Taru folloed by those of Pulosl Noshera, and Regi. The loest C as in the ater obtained from the river KabUl. The concentration of Pb ranged ppb; highest level as in the ater sample obtained from a nal near Tarnab (1.8 ppb) folloed by river-kabul (7.9 ppb). The amount of Pb in aters obtained from the ell Pulosi, tubeell Tehkal and tubeell NIFA ere higher than other aters tested. The concentration

3 ,- u U) -' 3V A 2: - _'.3V -t u U) I -oḻ1 3V u i -. Zn G -'.3,V U) W t -----{.-----t o c -. Stripping Time-Seconds Fig. 1. Potentiometric stripping curves obtained for Zn, Pb and Cd ith 25, 5,75 and 1 ppb in curves A, B, C and D respectively 158

4 Zn 7 Zn Y = x r =.994 n = 16 Cu y = r =.984 n = 16 6 frj 'Vi so I C \ «g'ci - 'c U5.S2 ọ ' Q vt ;{ J/. I. / /'»: o a -,---2;-b '--5' " '- Atomic Absorption Spectroscopy: I-lg g-1 Fig. 2. Correlation beteen the results abtained by AAS and PSA 159

5 " l.l. (,) l: N C\I ai co.2,... LO LO O'! O'! C'! O'! LO " C\I O M,... ( III.. I LO C\I CO C'! r: C\I c:q. < C\I C\I <D ai.. O'l ci,... C') C\I C\I CO - " ḻ: <D C':! C\I LO C\I O'! C':! O'l - l: )( os! LO <,...: LO..J := " -c <i O <D O C') <D (,),... LO "=': <D C\I r: o,...,...: CO ci < ai M - III..c: - ::1. C')..c: :I: c:q LO LO O'l r-,,... CO ".,...:,...,...: CO co,...: co -;,...: < l: III -III 'i: "C" (,)... 1 c:.. n;..c:.::t:. II) «s:..c:... :::I s (,). s Z Z..c: li5 -L ' -L -L :::I '1.Q. '6 "ii :::I II III...!. -L a: a...1.!. ::!: :. - c:... :::I :::I :::I :::I 3: c: o

6 of Cu ranged beteen ppb. The ater obtained from river Kabul as found to contain highest level of Cu than other aters. The loest Cu as in the ater from tubeell at Taru. The amounts of Cd ranged ppb among all the aters. The sample obtained from river Kabul had highest levels of Cd. Similarly the ater of this river had highest level of Zn (89.2 ppb). Hoever, the concentration of Zn in other ater samples as found beteen 16.8 and 28. ppb. It as interesting to find, that ater of river Kabul invariably contained higher levels of these heavy metals. The measurements of CV. revealed ide variation in Zn folloed by Cu, Cd, Pb, C and ph among these ater samples. The drinking aters generally had appreciable amounts of essential trace metals but lo contents of toxic metals such as Pb and Cd. This is useful for the people from nutrition point of vie. In vie of the importance of heavy metals in the health and nutrition of human beings and animals, several studies have been rried out in Pakistan and foreign countries (Sattar et al., 1989; Jattar and Saleem, 1987; Jelinek, 1982; Wolnik et al., 1985; Marietta et al., 1986). Hoever, little ork has been done on the heavy metal contents of food materials and aters in Pakistan, specially in the N.W.F.P. According to the Food and Nutrition Board (1974), the average daily requirements for human beings of Cu and Zn are 2 mg and 15 mg respectively. The joint FAO/WHO xpert Committee (1972) had set tolerable eekly intake limits for Pb and Cd as 3 mg and IJ.grespectively per person. Reliable base line data for heavy metals are not available in developing countries. The background values are needed for evaluating the toxicologil and nutritional signifince of consumption of these elements and their possible increase due to pollution. RFRNCS Benzo, Z, H. Schorin and M. Velose Simultaneous quantitative determination of manganese, iron, coper, zinc by atomic absorption spectroscoy in tropil cereals, fruits and legumes materials. J. Food Sci Danielsson, L. G, D. Jagner, M. Josefson and S. Westerlund Computersied potentiometric stripping analysis for the determination of dmium, lead, copper and zinc in biologil materials. Anal. Chim. Acta 127: FAOIWHO Joint xpert Committee on Food Additives valuation of certain food additives and the contaminants, mercury, lead and dmium. WHO Tech. Rep. Ser. 55: Food and Nutrition Board Recommended dietary alloances. National Ademy of Sciences, National Resarch Council, Washington D.C. Jattar, M. and M. Saleem Concentration of selected toxic trace metals in some vegetables and fruits of lol origin. Pak. J. Agric. Sci. 24: Jagner, D Instrumental approach to potentiometric stripping analysis of some heavy metals. Ana I. Chem. 5 : Jagner, D. and A. Graneli Potentiometric stripping analysis. Anal. Chim. Acta 83: Jagner, D Potentiometric stripping analysis for mercury. Anal. Chim. Acta 15: Jagner, D. and S. Westerlund Deter mination of lead, copper and dmium in ine and beer. Anal. Chim. Acta 117: Jagner, D. and K. Aren Potentiomet ric stripping analysis for zinc, dmium, lead and copper in sea ater. Anal. Chim. Acta 17: Jelinek, C.F Level of lead in the United States food supplies. J. Am. Oil Chemist's Soc 65: Khurshid., S. J. and I. H. Qureshi The 161

7 role of inorganic elements in the human body. The Nucleus 21: Marietta, G.P, L.G. Favretto and L. Favereno Cadmium in roadside grapes. J. Sci. Food Agric. 37: Qureshi, I.H, S. Ahmad, M.S. Chaudry and A. Mannan Neutron activation analysis of trace elemens in biologil materials. The Nucleus 21 : Satzger, R.,. Bonnin and F. I. Fricke Development of quality assurance programme for determination of ultratrace background levels of lead and dmium in ra agricultural crops by pulse anodic stripping vottarnrnetry.j, Am. Oil. Chemist's Soc. 67: US. Salinity Laboratory Staff Diagnosis and improvement of saline and alkali soils. USDA Handbook NO.6. Wolnik, K.A, F. L. Fricke, S.G. Capar, M.W. Meyer, R. D. Satzger,. Bonnin and C.M. Gaston lements in major ra agricultural crops in United States, 3-Cd, Pb and eleven other elements in rrots, field corn, onions, rice, spinach and tomatoes. J. Agric. Food Chern. 33:

Nutrient and heavy metal contents compared among five mushrooms from Pakistan

Karstenia 32:1-5. 1992 Nutrient and heavy metal contents compared among five mushrooms from Pakistan MUHAMMAD WAHID, ABDUS SATIAR and AFfAB IQBAL WAHID, M., SATTAR, A. & IQBAL, A. 1992: Nutrient and heavy