Acta Chim. Slov. 2010, 57, Technical paper. Özcan Yalçinkaya and Ali Rehber Türker* * Corresponding author:

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1 Act Chim. Slov. 2010, 57, Technicl pper A New Method for Indirect Determintion of Iodide nd Thiosulfte in Tble Slt nd Milk Bsed on Combintion of Solid-Phse Extrction nd Flme Atomic Absorption Spectrometry Özcn Ylçinky nd Ali Rehber Türker* Deprtment of Chemistry, Science nd Art Fculty, Gzi University, Ankr, Turkey * Corresponding uthor: E-mil: turker@gzi.edu.tr Received: Abstrct A new indirect method for the determintion of iodide nd thiosulfte ions in tble slt nd milk by flme tomic bsorption spectrometry ws described. This method is bsed on the reduction of chromium (VI to chromium(iii with the reducing ction of iodide nd/or thiosulfte, seprtion of unrected Cr(VI s its 1,5-diphenilcrbzide complex on column filled with Amberlite XAD-16, elution of the complex by 10 ml of 0.05 mol L 1 in methnol nd determintion by flme tomic bsorption spectrometry. Amount of the nlytes were clculted from the mount of Cr(VI rected with the nlytes. The optimum conditions for the determintion of iodide nd thiosulfte ions, including ph nd volume of smple solution were exmined. The effect of interfering species on the recovery of the iodide nd thiosulfte ions ws lso investigted. The precision of the proposed method is good s it provides reltive stndrd devition vlue of 3.5% for thiosulfte nd 4.5% for iodide during five replicte determintions of 10 µg ml 1 of thiosulfte nd 15 µg ml 1 of iodide, respectively. The ccurcy of the procedure ws tested by nlyzing spiked rel smples nd certified reference smple (BCR 150 Milk powder. The procedure described ws successfully pplied for the determintion of iodide in tble slt nd milk nd, thiosulfte in tble slt. Iodide nd thiosulfte ions hve been determined in rel smples with reltive error below 15%. Keyword: Iodide, thiosulfide, flme tomic bsorption spectrometry, Amberlite XAD-16, indirect determintion 1. Introduction Iodine exists minly s iodide nd iodte long with smll frction of orgnic iodine compounds in foods, sewter etc. Iodine ws used first commercilly in the form of potssium iodide s remedy for goiter, nd s iodoform, which ws used s disinfectnts for cuts nd for snittion. 1 Iodine is widely used in ctlysis s ctlyst, in some mnufcturing processes s stbilizer, in foods s dditives (iodiztion of slt nd minerl mixtures. Addition of iodine to tble slts is prt of preventive progrm for iodine deficiency disorder in mny countries. Slts re commonly iodized with potssium iodide. The verge iodine level of liver oil, soil, drinking wter nd sewter is bout mg kg 1, 2.8 mg kg 1, 8 11 µg L 1 nd 50 µg L 1, respectively. 1 Iodine is biologiclly essentil element s constituent of thyroid hormones nd its deficiency in the humn body cuses goitre nd other mlfunctions. The normtive dily iodine requirement of dult men ws found to be 1 ng g 1 body weight. 1 Iodine is ingested into n orgnism in food, hence monitoring of iodine intke from this resource is importnt. 2 Iodized slt, milk, eggs, diry products nd mrine fish re the min sources of iodine to food chin. The bove sources supply 74% of iodine intke, while 16% is supplied by vegetble food nd 10% by beverges. 1 The iodintion of industrilly used slt rised the iodine content of industril foods such s bred nd susge. The gretest contributors of iodine to humns re niml foodstuffs (75% nd vegetble foodstuffs (15%. The detection nd quntittive determintion of iodine in high concentrtions is possible by precipittion of AgI, PdI 2 nd HgI 2 or by Volhrd method. However, in lower concentrtions these methods re insufficient. In biologicl mterils, iodine determintions hve been crried

2 492 Act Chim. Slov. 2010, 57, out on the bsis of Sndell-Kolthoff technique during the pst 60 yers. 1 3 This technique is bsed on the rection of Ce(IV nd As(III ctlyzed by iodide nion nd spectrophotometric mesurement. Nowdys, iodine is determined by using inductively coupled plsm mss spectrometry (ICP-MS, 4 inductively coupled plsm opticl emission spectrometry (ICP-OES, 2 5 energy dispersive X-ry fluorescence nlysis, 6 chromtogrphic methods, 7,8 electrochemicl methods, 9,10 spectrophotometric methods, 11,12 neutron ctivtion nlysis 13 re lso used for the determintion of iodine. Thiosulfte is n oxynion of sulfur produced by the rection of sulfite ions with elementl sulfur in boiling wter. Thiosulfte occurs nturlly in hot springs nd geysers, nd is produced by biochemicl processes. Thiosulftes re stble only in neutrl or lkline solutions, but not in cidic solutions, due to decomposition to sulfite nd sulfur. Thiosulfte is used in pper industry to hlt bleching, in lether industry, in textile industry to set dye, in photogrphy to dissolve the silver slts from photogrphic film nd in vrious chemicl processes s chlorine-removing gent. The determintion of thiosulfte, sulfite nd sulfide in their mixtures is difficult becuse they re lbile nd prticipte in complex equilibri with other sulfur compounds formed by their uto-redox rections. 14 Unfortuntely, there re few mesurement methods vilble t or below µg g 1 levels for simultneous determintion of these compounds, especilly in complex mtrices. Vrious instrumentl methods, such s spectrophotometry, 15,16 mperometry, 17 voltmmetry, 18 polrogrphy, 19 ion-exclusion chromtogrphy, 20 cpillry electrophoresis, 21 ion chromtogrphy 22 nd high performnce liquid chromtogrphy 23 hve been proposed for the determintion of thiosulfte. The bove mentioned methods re sensitive to the determintion of both iodide nd thiosulfte. However, some of them hve disdvntges such s their high cost, often tedious, complicted nd/or time-consuming, nd proneness to interferences. Recently, indirect determintions of thiosulfte nd especilly iodine by tomic bsorption spectrometry re widely used It is recognized tht flme tomic bsorption spectrometry (FAAS should be preferred to bove methods if both of these methods cn be pplied for ny smple due to some dvntges of this method such s low cost, short time of nlysis, nd simplicity. Atomic bsorption spectrometer is nlyticl instrument vilble in most nlyticl lbortories. This technique hs been proved s suitble tool for the indirect determintion of orgnic compounds, incresing the rnge of species ccessible with such spectrometers. Bermejo-Brrer et l. proposed n indirect method for the determintion of iodide. 25 In tht study, the iodide contined in the smple is oxidized to iodine, which is distilled by mens of microwve energy nd reduced bck to iodide. This iodide is combined with Hg(II nd 2,2 -dipyridyl to give n ion pir, which is selectively extrcted into isobutylmethylketone (IBMK. Mercury is determined in the extrct by electrotherml tomic bsorption spectrometry (ETAAS in order to determine iodide. In nother study, method to determine iodide is developed, bsed on the formtion of n ion pir between 1, 10-phennthroline, mercury(ii nd iodide tht cn be selectively extrcted into IBMK. IBMK lyer ws nlyzed by ETAAS for mercury nd then iodide ws quntified. 26 Hse nd Broekert used the interference cused by iodide in the determintion of mercury by FI-CVAAS for indirect determintion of iodide. 28 Yebr nd Cespon proposed n indirect flow injection tomic bsorption spectrometric method for the determintion of iodide in tp nd se wter bsed on the reduction of Cr(VI to Cr(III in cid medium. 29,30 The Cr(III formed ws retined online, proportionl to the iodide concentrtion in the smple, on poly(minophosphonic cid chelting resin, which is only selective for this oxidtion stte. Reduced Cr(III ws preconcentrted on the column, eluted with HCl solution nd determined by FAAS. The proposed method llows the determintion of iodide in the µg L 1 rnge with reltive stndrd devition of 2.7%. 29 This pper describes new method for the indirect determintion of thiosulfte nd iodide in tble slt nd milk bsed on combintion of solid-phse extrction nd flme tomic bsorption spectrometry. It ws bsed on the reduction of known excess mount of Cr(VI by iodide nd thiosulfte followed by the seprtion of non-reduced Cr(VI from product of Cr(III by column solid phse extrction s its diphenylcrbzide (DPC complex nd determintion of the non-reduced mount of Cr(VI in the eluent by FAAS. Seprtion nd specition of Cr(VI nd Cr(III by solid phse extrction on column filled with Amberlite XAD-16 hd been optimized in our previous study. 31 Here, vrious nlyticl prmeters such s smple volume, flow rte nd ph were optimized. The proposed method hs lredy been pplied to the indirect determintion of scorbic cid in some drug nd fruit juice smples successfully before. 32 In this study, the developed chromium specition method ws dpted for the determintion of iodide nd thiosulfte nd optimum experimentl conditions were investigted. The developed method ws pplied for the determintion of iodide in tble slt nd milk, nd thiosulfte in tble slt. 2. Experimentl Instrumenttion A Philips PU 9285 model tomic bsorption spectrometer equipped with deuterium lmp bckground corrector nd with n ir cetylene burner ws used for the nlysis under the conditions suggested by the mnufcturer. Chromium hollow cthode lmp ws used to mesure the bsorbnce of chromium. The operting conditions

3 Act Chim. Slov. 2010, 57, were s follows: Wvelength, nm; lmp current, 12 ma; bndpss, 0.5 nm nd fuel flow rte, 1.4 L min 1. Deuterium lmp bckground correction ws used. All ph mesurements were mde with Consort digitl ph meter nd combined glss electrode Regents All solutions were prepred using nlyticl regent grde chemicls unless otherwise specified nd doubly distilled deionized wter. Stndrd solutions of iodide nd thiosulfte ions, 1000 µg ml 1, were prepred dily by dissolving g of KI (Merck nd g of N 2 O 3.5 O, respectively in wter nd diluted to 100 ml with wter in volumetric flsk. 1,5-diphenylcrbzide (DPC solution (0.01 mol L 1 ws prepred dily by dissolving pproprite mount of DPC (Merck in 5 ml of cetone (Merck nd diluting to 25 ml with wter. The solution ws kept in n mber-glss bottle. A solutions of 1000 µg ml 1 Cr(VI ws prepred by dissolving g of K 2 Cr 2 O 7 (Merck in wter nd diluted to 100 ml with wter in volumetric flsk. (95 98%, Merck nd methnol (Merck were used. Amberlite XAD-16 Resin (Room nd Hss; surfce re, 800 m 2 g 1 ; wet mesh size, mesh ws used fter wshing with methnol, 1 mol L 1 HCl solution nd wter, respectively nd dried for 2 h t 60 C Column Preprtion A glss column (150 mm length 10 mm i.d with glss-wool over its stopcock ws used s mini column. A totl of 300 mg of Amberlite XAD-16 resin ws dded in wter nd then the slurry obtined ws plced into the column to obtin bed height of bout 1.5 cm. A smll mount of glss-wool ws plced on top to void disturbnce of dsorbent during smple pssge. The column ws preconditioned by pssing blnk solution hving sme ph with the smple solution prior to use. After ech use, the resin in the column ws wshed with dilute HCl nd with wter, respectively nd stored in wter for the next experiment Preprtion of Smples Commercilly vilble tble slt ws used s smple. As it ws known tht tble slt contins both iodide nd thiosulfte, smple solution ws prepred in two different wys: ( ± g of slt smple ws weighed in 50 ml volumetric flsk, nd 20 ml of deionized wter nd 5 ml of 1 mol L 1 were dded to dissolve the smple. The solution ws diluted to 50 ml with wter to obtin 0.1 mol L 1. This smple ws used for thiosulfte determintion. ( ± g of slt smple ws weighed in 50 ml volumetric flsk, nd 20 ml of deionized wter nd 2.7 ml of concentrted (d = 1.84 g ml 1, 98% m/m were dded to dissolve the smple. It ws diluted to 50 ml with wter to obtin 1 mol L 1. This smple ws used for the determintion of totl content of iodide nd thiosulfte. Two pckges of psteurized milk (totlly 2 L of milk were purchsed from the locl mrket. Then, two pckges of milk ws poured into 2 L beker nd mixed thoroughly. 200 ml of milk smple ws tken into 250 ml beker nd 10 ml of concentrted HCl ws dded to the smple to precipitte proteins. After the precipittions completed, the obtined mixture ws filtered through Schwrzbnd filter pper (Crl Schleicher & Schüll. The filtrte ws evported until the volume decresed to bout 50 ml. By dding concentrted sulfuric cid to the filtrte, concentrtion of sulfuric cid ws djusted to bout 1 mol L 1. This smple ws used for the determintion of iodide by the procedure given below. Accurtely weighted (bout 5 g mount of certified reference mteril (BCR 15 Milk powder ws treted with 4 ml of wter nd 0.5 ml of concentrted HCl to precipitte proteins. Then, the obtined mixture ws filtered through Schwrzbnd filter pper (Crl Schleicher & Schüll. By dding concentrted sulfuric cid to the filtrte, concentrtion of sulfuric cid ws djusted to bout 1 mol/l. This smple ws used for the determintion of iodide by the procedure given below Procedure In order to prepre synthetic spiked smple solution, 1.2 ml of 100 µg ml 1 Cr(VI, 10 ml of 15 µg ml 1 iodide (or 10 ml of 10 µg ml 1 thiosulfte nd 1 ml of 0.01 mol L 1 DPC solution were dded into 100 ml volumetric flsk nd the volume is djusted to 100 ml with wter. For the nlysis of rel smples, 10 ml of prepred smple solutions ws tken insted of the solution of iodide nd/or thiosulfte ions. Then, ph of the smple solution ws djusted to the desired vlue (ph = 1 t which the recovery of Cr(VI is the highest with sulfuric cid. The resulting solution ws pssed through the column t the desired flow rte (1.5 ml min 1. The retined chromium (VI-DPC complex on the column ws eluted with 10 ml of 0.05 mol L 1 solution in methnol. Chromium content in the elute ws determined by FAAS. Iodide nd thiosulfte content were clculted by using stoichiometric reltionship between Cr(VI nd iodide nd thiosulfte ions (1 g of Cr(VI is equivlent to 7.33 nd 3.23 g of iodide nd thiosulfte ions, respectively. The rection schemes re s follows: Cr 2 O I + 14 H + 2 Cr I O Cr 2 O O H + 2 Cr S + 7 O Non-reduced Cr 2 O DPC Cr-DPC complex

4 494 Act Chim. Slov. 2010, 57, Cr-DPC complex + Amberlite XAD-16 Adsorbed Cr-DPC onto Amberlite XAD-16 Cr-DPC onto Amberlite XAD-16 + Eluent Elution solution contining Cr(VI 3. Results nd Discussion Optimiztion of Column solid Phse Extrction of Chromium Species Optimiztion of the prmeters such s ph of the smple solution, eluent type, smple volume, mount of dsorbent, flow rte of smple solution effecting the column solid phse extrction of chromium species (Cr(III nd Cr(VI were investigted nd reported in our previous pper. 31 Quntittive recovery (> 95% ws found t the ph 1 with Cr(VI while the recovery of Cr(III is rther low (< 5%. This could mke it possible to seprte Cr(VI from Cr(III. 31 Optimum vlues found for the determintion of Cr(VI ws given in Tble 1. The linerity of this system ws evluted for chromium concentrtion rnging from 1 to 5 mg L 1 under the experimentl condition mentioned bove. The clibrtion grph ws found to be liner up to 5 mg L 1 with regression coefficient bove The detection limit, s the concentrtion corresponding to three times the stndrd devition of the blnk signl (n = 12 ws 45 µg L 1 for Cr(VI. 31 Tble 1 Optimum conditions for preconcentrtion/seprtion of Cr(VI by the Amberlite XAD Prmeter Vlue ph 1 Eluent (0.05 mol L -1 solution in methnol volume, ml 10 Amount of dsorbent (mg 300 Flow rte of the smple solution (ml min Volume of the pplicble smple solution (ml (Contining 10 µg Cr(VI 250 Acidity of redox rections (, mol L Effect of Acidity The proposed procedure of indirect determintion of iodide nd thiosulfte ws bsed on its reducing ction on Cr(VI in cidic medium nd following the tomic bsorption spectrometric determintion of the remining Cr(VI fter seprting the Cr(VI from Cr(III by column solid phse extrction of Cr(VI s its DPC complex onto Amberlite XAD-16. Amberlite XAD-16 resin is selective only for Cr(VI. The dependence of the redox rection between Cr(VI nd iodide or thiosulfte on the cidity of the solution is one of the importnt prmeters tht cn hve sig Determined experimentlly in this study nificnt influence on the over-ll performnce of the indirect method. Oxidtion of both iodide nd thiosulfte with Cr(VI is quntittive in the medium of 1 mol L 1. However, in 0.1 mol L 1, only thiosulfte cn be oxidized by Cr(VI. Therefore, optimum cidity of medium of the redox rections ws djusted to 0.1 mol L 1 for thiosulfte determintion nd 1 mol L 1 for iodide nd/or totl iodide nd thiosulfde determintion. After the redox rection ws completed, ph of the mixture ws djusted to the rnge of using diluted sulfuric cid which ws found s optimum ph for solid phse extrction of chromium species before Effect of Volume of Smple Solution (Anlyte Concentrtion The effect of chnges in the volume of smple solution pssed through the column on the recovery of iodide nd thiosulfte ws investigted in order to determine n pplicble smple volume or minimum iodide nd thiosulfte concentrtion. For tht purpose, 10, 25, 50 nd 100 ml of smple solutions contining fixed mount of iodide nd thiosulfte (150 µg nd 100 µg, respectively corresponding to 15, 6, 3 nd 1.5 µg ml 1 for iodide nd 10, 4, 2 nd 1 µg ml 1 for thiosulfte, respectively, were pssed through the column under the optimum conditions determined experimentlly. It ws found tht iodide nd thiosulfte could be recovered up to 50 ml of smple solution with reltive error of bout 10 % (Tble 2. At higher smple volumes, the recoveries decresed nd the reltive error incresed grdully with incresing volume of smple. It cn be concluded tht 3 µg ml 1 iodide nd 2 µg ml 1 thiosulfte could be determined by this method for 50 ml smple volume. Tble 2 Effect of smple volume on the determintion of iodide nd thiosulfte Anlyte Volume of Added Found * Reltive smple solution µg ml 1 µg ml 1 error, ml % Iodide ± 0.8 4, ± ± , ± Thiosulfte ± ± ± ± Interference Studies To ssess the vlidity of the method, study of interference for iodide nd thiosulfte determintion ws lso performed. The ctions in the smple would not interfere

5 Act Chim. Slov. 2010, 57, with the determintion of iodide nd thiosulfte becuse they re not dsorbed by Amberlite XAD-16 resin column. The interfering effect of the ctions on the seprtion nd determintion of Cr(VI hd been investigted in our previous study. 31 Recovery of Cr(VI ws quntittive when the rtio of interfering ions to chromium (VI ws 10 for Fe(III, 25 for Pb(II nd Al(III, 50 for Cu(II, Ni(II, Mn(II, Co(II nd 100 for Zn(II, Cd(II, N(I, K(I, Mg(II nd C(II. 31 The interfering effect of chloride, bromide, glucose, citric cid, scorbic cid tht re commonly found in the smples nlyzed were investigted by dding different mount of other species to solution contining 15 µg ml 1 iodide nd 10 µg ml 1 thiosulfte. The interference effect of nlytes to ech other ws lso studied. The results re listed in Tbles 3 nd 4. According to this work, no interferences were observed in iodide determintion for glucose nd citric cid up to 30 µg ml 1, for bromide up to 750 µg ml 1 nd for chloride up to µg ml 1 (reltive error < 10%. However, scorbic cid nd thiosulfte interfered with determintion of iodide bove 10 µg ml 1. In thiosulfte determintion, iodide lso interfered with the determintion bove 100 µg ml 1. It ws concluded tht from these results, iodide cn not be determined ccurtely in the smples contining scorbic cid nd/or thiosulfte. Both of the iodide nd scorbic cid nd/or thiosulfte re oxidized by Cr(VI in Tble 3 The effect of some species on the recovery of iodide (ph, 1; eluent, 10 ml of 0.05 mol L 1 solution in methnol; smple volume, 10 ml; mount of the iodide, 100 µg Interferent Concentrtion Reltive species Added Found error of interfering µg ml 1 µg ml 1 % µg ml 1 Chloride ± ± ± ± ± ± Bromide ± ± ± ± ± Ascorbic cid ± ± Glucose ± ± ± Citric cid ± ± ± Tiosulfte ± ± Tble 4 The effect of some species on the recovery of thiosulfte (ph, 1; eluent, 10 ml of 0.05 mol L 1 solution in methnol; smple volume, 10 ml; mount of the thiosulfte, 100 µg Interferent Concentrtion Reltive species Added Found error of interfering µg ml 1 µg ml 1 % µg ml 1 Chloride ± ± ± ± Bromide ± ± ± ± Iodide ± ± ± given experimentl conditions (1 mol L 1. As cn be seen in our previous study, scorbic cid cn lso be oxidized in 0.1 mol L 1 medium 32 nd t tht condition iodide does not oxidize nd therefore does not interfere with the determintion of scorbic cid. In order to overcome the scorbic cid nd thiosulfte interferences, two different experimentl conditions (1 mol L 1 nd 0.1 mol L 1 should be pplied. While t the presence of 1 mol L 1, totl Cr(VI content rected with scorbic cid, thiosulfte nd iodide is determined, t the presence of 0.1 mol L 1, Cr(VI content rected with only scorbic cid nd thiosulfte is determined. The difference in Cr(VI contents corresponds the Cr(VI rected with iodide. Results obtined for different experimentl conditions were given in Tble Precision nd Accurcy of the Method In order to investigte the precision of the method, the generl procedure given bove ws pplied to the determintion of iodide nd thiosulfte in synthetic smple solution contining 15 µg ml 1 iodide nd 10 µg ml 1 thiosulfte, seprtely. Results of successive determintions were given in Tble 6. The precision of the proposed method is good s it provides reltive stndrd devition vlue of 4.5% nd 3.5% during five replicte determintions of 15 µg ml 1 of iodide nd 10 µg ml 1 thiosulfte, respectively. The ccurcy of the method ws lso checked by clculting reltive error (< 7%. In order to check the ccurcy of the proposed method, iodide hs been determined in certified reference mteril (BCR 150 Milk powder by the proposed method. Four determintions hve been performed on the four smple portions by pplying dissolution nd test procedure given bove. Good greement ws obtined between

6 496 Act Chim. Slov. 2010, 57, Tble 5 Determintion of iodide nd thiosulfte in synthetic smple Anions (Condition Thiosulfte, µg g 1 Iodide, µg g Rected Cr(VI 1 Lbeled Found * Reltive Lbeled Found * Reltive µg ml 1 error, % error, % O I 6.13 ± 0.06 (1 mol L 1 2 O ± ± ± (0.1 mol L I 1.88 ± 0.06 the estimted content by the proposed method nd the certified vlues for the iodide. It ws found tht there is no significnt difference between the results found by the proposed method (1.10 ± 0.08 µg g 1 s the men of four determintions t 95% confidence level nd the certified vlues (1.29 ± 0.09 µg g 1 ccording to the t-test. It cn be concluded tht there is no systemtic error in the determintion t 95 % confidence level (the reltive errors re below 15%. The reltive error is cceptble level for quntittive trce nlysis. These results lso indicte tht the Tble 6 Accurcy nd precision of the method of iodide nd thiosulfte determintion in synthetic smple Added Found Reltive error, RSD, % µg ml 1 µg ml 1 % Iodide ± Thiosulfte ± developed method is not ffected by potentil interferences from the mjor mtrix elements of the nlyzed reference mteril Appliction To investigte the pplicbility to rel smples, the proposed method hs been pplied to the determintion of iodide in tble slt nd milk, nd thiosulfte in tble slt (Tbles 7 nd 8. As shown in the Tbles, the recoveries of iodide nd thiosulfte dded to tble slt nd milk were ll close to 100%. The results of recovery test re very good. No interference ws found in view of the presence of very complex mtrix of the smples (especilly milk s indicted by the good recovery of iodide (bout 90%. The proposed method could be pplied to determintion of iodide in iodized slt nd milk, nd thiosulfte in iodized slt without interference from other constituents of smples encountered. Tble 7 Iodide nd thiosulfte determintion in tble slt Anions (Condition Thiosulfte, µg g 1 Iodide, µg g Rected Cr(VI 1 Lbeled Found * Reltive Lbeled Found * Reltive µg ml 1 error, % error, % O I 3.76 ± 0.06 (1 mol L 1 2 O ± ± ±0.6 5 (0.1 mol L I 0.60 ± 0.04 Tble 8 Determintion of iodide in milk Smple Added, µg ml 1 Found *, µg ml 1 RSD, % Reltive error, % Milk 0.86 ± ±

7 Act Chim. Slov. 2010, 57, Conclusions The proposed method, using the rection between iodide nd thiosulfte nd Cr(VI, is bsed on the off-line preconcentrtion/seprtion by column solid phse extrction nd flme tomic bsorption spectrometric indirect determintion of iodide nd thiosulfte. This method provides interference free determintion of iodide nd thiosulfte due to prior seprtion of Cr(VI from the interfering species. The proposed method could be pplied to the nlysis of tble slts contining different mount of iodide nd thiosulfte without interference from other constituents encountered. The method is sensitive, selective nd suitble for lbortory rutin control. Repeted use of column is possible. 5. Acknowledgments The uthors re grteful for the finncil support of BAP Projects of Gzi University (05/ References 1. E. Merin, M. Anke, M. Ihnt, M. Stoeppler: Elements nd their compounds in the Environment, Wiley-VCH, Weinheim, 2004, Vol 3, 2 nd Ed, E. Niedobov, J. Mchát, V. Otrub, V. Knicky, J. Anl. At. Spectrom. 2005, 20, P. Jopke, M. Bhdır, J. Fleckenstein, E. Schung, Commun. Soil. Sci. Plnt Anl. 1996, 27, J. Nozuk, M. A. M. S. deveig, P. V. Oliveir, E. de Oliveir, J. Anl. At. Spectrom. 2003, 18, T. Nkhr, T. Mori, J. Anl. At. Spectrom. 1994, 9, V. Y. Zichick, S. V. Zichick, J. Trce Microprobe T. 1999, 17, S. Anderson, U. Forsmn, J. Chromtogr. B 1997, 692, K. Ito, T. Ichihr, H. Zhuo, K. Kummoto, A. R. Timerbev, T. Hirokow, Anl. Chim. Act 2003, 497, L. Tin, L. Liu, L. Chen, N. Lu, H. Xu, Tlnt 2005, 66, O. Chilpkul, M. Amttongchi, P. Wilirt, K. Grudpn, D. Ncprich, Tlnt 2004, 64, Z. Xie, J. Zho, Tlnt 2004, 63, M. Soylk, Ü. Divrikli, L. Elçi, M. Doğn, Fresenius Environ. Bullet. 2001, 10, Y. Gélins, G. V. Iyengr, R. M. Brnes, Fresenius J. Anl. Chem. 1998, 362, T. Koh, K. Okbe, Anl. Sci. 1992, 8, T. Koh, T. Sugimoto, M. Mtsui, Y. Miur, Tlnt 1997, 44, M. Okumur, K. Fujing, Y. Seike, A. Ngshim, Bunseki Kgku 1998, 47, P. Wng, Y. Yun, X. Y. Jing, G. Y. Zhu, Tlnt 2001, 53, I. Ciglenecki, B. Cosovic, Electronl. 1997, 9, H. S. Kll, M. Ghdiri, A. A. M. Beigi, S. A. S. Sdjdi, Anl. Chim. Act 2004, 502, J. M. Xu, Y. P. Wng, Y. Z. Xin, H. Li, L. T. Jin, K. Tnk, H. Hrguchi, A. Itoh, Chromtogrphi 2002, 56, Z. Dunorvicius, A. Pdrusks, Electrophoresis 2002, 23, Y. Miur, M. Htkeym, T. Hosino, P. R. Hddd, J. Chromtogr. A 2002, 956, R. Kondo, N. Ksshim, H. Mtsud, Y. Ht, Fisheries Sci. 2000, 66, D. Chkrborty, A. K. Ds, Atom. Spectros. 1988, 9, P. Bermejo-Brrer, M. Abol-Somoz, A. Bermejo-Brrer, M. L. Cerver, M. De L Gurdi, J. Anl. Atom. Spectrom. 2001, 16, P. Bermejo-Brrer, R. M. Anllo-Sendin, M. Abol-Somoz, A. Bermejo-Brrer, Mikrochim. Act 1999, 131, P. Bermejo-Brrer, A. Moredpineiro, M. Abolsomoz, J. Moredpineiro, A. Bermejo-Brrer, J. Anl. Atom. Spectrom. 1994, 9, O. Hse, J. A. C. Broekert, Spectrochim. Act 2003, 57B, M. C. Yebr, R. M. Cespon, Fresenius J. Anl. Chem. 2000, 367, M. C. Yebr, R. M. Cespon, Anl. Chim. Act 2000, 405, A. Tunçeli, A. R. Türker, Tlnt 2002, 57, A. R. Türker, Ö. Ylçınky, A. Tunçeli, J. Food Drug Anl. 2008, 16, Povzetek Opisn je nov metod dolo~evnj jodid in tiosulft v kuhinjski soli in mleku s plmensko tomsko bsorpcijsko spektrometrijo. Osnovn je n redukciji Cr(VI v Cr(III zrdi prisotnosti jodid in/li tiosulft, rekciji prese`neg Cr(VI z 1,5-difenilkrbzidom in njegovi lo~bi n koloni polnjeni z ionsko izmenjlno smolo Amberlite XAD-16. Po spirnju kolone z 10 ml 0,05 M v metnolu dolo~imo koncentrcijo prese`neg Cr(VI s plmensko tomsko bsorpcijsko spektrometrijo. V prispevku so podni optimlni pogoji z dolo~evnje jodid in tiosulft, kot so ph, volumen vzorc in vpliv mote~ih ionov. Reltivni stndrdni odmik petih meritev vzorcev s koncentrcijo tiosulft 10 µg ml 1 in koncentrcijo jodid 15 µg ml 1 je 3,5 % ozirom 4,5 %. To~nost metode je bil preverjen z nlizo referen~neg vzorc (BCR mleko v prhu in relnih vzorcev kuhinjske soli in mlek v prhu. Reltivne npke meritev so bile v vseh primerih mnj{e od 15 %.