SOLID PHASE EXTRACTION OF AND IONS BY A NEW CARBOTHIOAMIDE DERIVATIVE DUYGU OZDES, CELAL DURAN b,, HACER BAYRAK b, HUSEYIN SERENCAM c, HASAN BASRI SENTURK b Gumushne Voctionl School, Gumushne University, Gumushne 29100, Turkey b Deprtment of Chemistry, Fculty of Sciences, Krdeniz Technicl University, Trbzon 61080, Turkey c Fculty of Engineering, Deprtment of Food Engineering, Byburt University, Byburt 69000, Turkey (Received: Jnury 18, 2013 - Accepted: April 17, 2013) ABSTRACT An effective, simple, low cost nd ccurte sorption spectrophotometric pltform for the extrctions nd subseuent untifictions of nd ions in food nd environmentl smples hs been described in this disserttion. The seprtion nd preconcentrtion of the nlyte ions were ccomplished by solid phse extrction method bsed on the dsorption of their N (4 methylphenyl) 2 {[(4 phenyl 5 pyridin 4 yl 4H 1,2,4 trizol 3 yl)thio]cetyl} hydrzinecrbothiomide (MFPTAHK) complex on Amberlite XAD 8 resin in mini column. The developed method ws systemticlly investigted in different set of experimentl prmeters tht influence the seprtion nd preconcentrtion of nd ions. The precision of the method ws determined by reproducibility studies nd expressed s reltive stndrd devitions (RSD %) which were less thn 4% for both nlyte ions. The limits of detections (LODs) for nd ions bsed on the three times the stndrd devition of the blnks (N:10) were found to be 0.31 µg L 1 nd 0.86 µg L 1, respectively. The developed SPE procedure ws utilized for the simultneous extrction nd determintions of nd ions levels in rice, crcked whet nd red lentil s food smples nd vrious wter smples. Keywords: Solid Phse Extrction, N (4 methylphenyl) 2 {[(4 phenyl 5 pyridin 4 yl 4H 1,2,4 trizol 3 yl)thio]cetyl}hydrzinecrbothiomide, Flme tomic bsorption spectrometry, Cdmium(II), Led(II) INTRODUCTION Contmintion of environment with hevy metls is widely incresing due to their industril pplictions. Although necessry precutions re tken, pollution from industries increses dy-by-dy with the development of modern technology. Severl hevy metls nd metlloids, such s rsenic, mercury, cdmium, nd led re hzrdous for living orgnisms when digested t bove certin concentrtion levels 1. Environmentl pollution cused by the forementioned metls my originte from vriety of industril pplictions such s electrolysis for vrious purposes, csting industry, surfce finishing processes for metls, tnnery nd bttery mnufcturing 1 4. Led is n extremely hrmful trce element even t very smll mounts. It hs been proven tht led is neurotoxin nd cuses dverse centrl nd peripherl effects 5. On the other hnd, led poisoning is wide spred environmentl helth problem in the present-dy sitution 6, 7. Moreover cdmium is toxic substnce, present bout in ech ecosystem round the world. The hlf-life of this metl is in the rnge of 10 30 yers, nd its ccumultion in humn body cuses cute nd chronic metbolic disorders, such s iti-iti disese, nd lso ffects the vitl orgns 4, 8, 9. Powerful nlyticl tools nd severl sensitive instrumentl techniues hve been developed for trce element determintion s result of rpid growth in instrumenttion 10. The direct ppliction of vrious determintion techniues is generlly difficult due to the lower levels of the nlyte ions thn the detection limit nd the complicted mtrix interferences 11. Therefore, in most cses seprtion nd preconcentrtion techniue such s solid phse extrction (SPE) 12, solvent extrction 13, coprecipittion 14, electrochemicl deposition 15, cloud point extrction 16, liuid-liuid-extrction 17, ion-exchnge 18, nd membrne filtrtion 19 re employed prior to instrumentl detections of trce metl ions. SPE hs mny dvntges over different smple pretretment methods, including reduced nlysis time, decresed solvent usge nd disposl, clener extrcts nd high cpcity nd regenerbility of the used dsorbent 20. Vrious types of sorbents such s Amberlite resins 21, ctivted crbon 22, Diion HP 2MG 23, silic gel 24, polyurethne fom 25 nd hydrogel 26 hve been developed for SPE of different types of metl ions. Among these sorbents Amberlite XAD 8, used in this study, is polycrylic cid ester polymers with 160 m 2 g 1 surfce re, 0.79 mg g 1 pore volume, 225 Å pore dimeter nd 40 60 bed mesh size, nd recently, it hs been used successfully s sorbent in few solid phse extrction studies 27, 28. This pper describes n pproch to develop sensitive, sfe, rpid, simple nd low cost seprtion nd preconcentrtion method bsed on SPE for the ccurte determintions of nd ions level in environmentl nd food smples by flme tomic bsorption spectrometry (FAAS). In the presented method we hve pcked the mini-column with Amberlite XAD 8 s non-polr resin, nd the metl ions hve been retined on the resin s their N (4 methylphenyl) 2 {[(4 phenyl 5 pyridin 4 yl 4H 1,2,4 trizol 3 yl)thio]cetyl}hydrzinecrbothiomide (MFPTAHK) complexes. Before pplying the method to se nd strem wter s liuid smples nd rice, crcked whet, nd red lentil s solid smples, vrious prmeters tht influence the untittive recoveries of nd ions, including ph, eluent type, concentrtion nd volume, untity of lignd, smple volume, nd mtrix ions were investigted for optimiztion of the presented procedure. Also the vlidtion of the method ws evluted by the nlyte ddition/recovery tests. EXPERIMENTAL Instruments A Perkin Elmer AAnlyst 400 model flme tomic bsorption spectrometer (Überlingen, Germny) euipped with deuterium bckground corrector nd hollow-cthode lmps were used to determine metl ions concentrtion in the ueous solution. A digitl desktop ph meter (Hnn Instruments Model ph 211, Cluj-Npoc, Romni) with glss electrode ws employed to djust the ph of the solutions. Milestone Ethos D closed vessel microwve system (Milestone Inc., Sorisole (BG), Itly) ws operted for obtining the cler solutions by digesting the solid smples. The instrumentl prmeters were chosen s recommended by the mnufcturer. Regents nd solutions All of the chemicls, except the orgnic complexing gent, used in both reserch nd routine lbortory studies, were nlyticl grde nd obtined from Merck (Drmstdt, Germny) or Fluk (Buchs, Switzerlnd). The stock solutions of the selected metl ions were prepred freshly by dissolving pproprite mounts of their nitrte slts nd the working solutions of the nlyte ions were prepred by diluting the stock solutions of them. Dilute HNO 3 nd NOH solutions were used for ph djustments. Amberlite XAD 8 resin, used s sorbent in this study, ws purchsed from Sigm Aldrich Chemicls (St. Louis, MO, USA). The lignd, MFPTAHK, used in this study ws synthesized in the orgnic chemistry reserch lbortory (Chemistry Deprtment, Fculty of Science, Krdeniz Technicl University). The detiled informtion for its synthesis ws given in the literture 29. The necessry precutions were tken when 2204 e-mil: cdurn@ktu.edu.tr
MFPTAHK ws hndled in the experiments becuse there ws no sfety dt vilble on its usge in the literture. Smpling nd pre-tretments Se wter (Trbzon Port, Blck Se/Turkey) nd strem wter (Degirmendere Strem, Trbzon/Turkey) used in this study were smpled using pre-clened polyethylene bottles. The wter smples were filtered immeditely using nitro-cellulose membrne with pore size of 0.45 µm fter being collected nd stored t 4 C until they were used. The developed SPE procedure ws lso pplied to vrious solid smples; rice, crcked whet nd red lentil (Lens culinris). The solid smples were digested with closed vessel microwve system prior to the ppliction of the present SPE procedure. For this purpose, 1.000 g of rice, crcked whet nd red lentil were weighed into teflon vessels, seprtely nd 6 ml of HNO 3 nd 2 ml of H 2 O 2 were dded into the vessels. The digestion of the solid smples by microwve rdition ws performed in four steps: 6 min for 250W, 6 min for 400W, 6 min for 650W, nd 6 min for 250W. During ll these microwve rditions the pressure ws kept t 45 brs, nd the ventiltion ws 3 min. At the end of the microwve digestion, the smple volume ws completed to 100 ml with distilled/deionized wter nd then the method ws pplied to them. Preprtion of SPE column The seprtion nd preconcentrtion of nd ions were chieved with glss mini column, hving 13 cm length 1.0 cm dimeter, porous disk nd stopcock. 250 mg of Amberlite XAD 8 resin beds ws plced into the column. The column ws firstly wshed with 10 ml of 2 M HNO 3 solution nd then wshed with distilled/deionized wter until it is free from cid. After ech cycle of preconcentrtion nd elution experiments, the resin in the column ws wshed thoroughly with distilled/deionized wter nd then stored in distilled/deionized wter for further ppliction. Fig.1. Effect of ph on the recoveries of nlyte ions (N: 3, smple volume: 50 ml, untity of MFPTAHK: 8.0 mg) Generl Procedure The solid phse extrction of 2.0 µg of nd 10.0 µg of ions present in 50 ml of ueous solution ws crried out by djusting the ph to 6.5 by dding either diluted HNO 3 or NOH solutions in the presence of 8.0 mg (2.0 ml 0.4% (w/v)) of MFPTAHK. The solution ws left to stnd for 10 minutes in order to mke sure tht the formtion of metl MFPTAHK complex ws completed. Then the resulting solution ws pssed through the column with flow rte of 20 ml min -1. The metl MFPTAHK complex retined in the resin ws eluted with 10 ml of 2.0 mol L 1 HNO 3 in cetone nd the eluent ws evported to ner dryness on hot plte. The volume of the residue ws completed to 2.0 ml with distilled/deionized wter nd the solution ws nlyzed by FAAS. RESULTS AND DISCUSSION Optimiztion prmeters The untittive retention of the nlyte ions re strongly ffected by the ph of the ueous solutions. The effect of ph chnge on the seprtion nd preconcentrtion of nd ions ws evluted by chnging the ph of the smple solutions from 2.0 to 10.0 by using either diluted HNO 3 or NOH solutions. As cn be seen in the extrction curve of nd ions (Fig. 1), the recovery of the nlyte ions ws lmost constnt between ph 6.0 nd 7.0, then it decresed gretly from ph 8 up to 10. At ph vlues lower thn 6.0, the untittive recoveries (>95%) for nd ions cnnot be chieved hence in ll subseuent experiments the ph vlue ws selected s 6.5. To obtin the optiml untity of complexing gent for both forementioned metl ions, the effect of untity of MFPTAHK ws exmined by using different mounts of it in the rnge of 0 12.0 mg. It hs been observed tht the recovery yields of the nlyte ions incresed with the increse in the untity of complexing gent, MFPTAHK, up to certin level. The yield of the recoveries for both nd ions were not untittive (16% nd 42%, respectively), when MFPTAHK ws not dded to the solution. As shown in Figure 2, the recovery vlues incresed rpidly with incresing the untity of MFPTAHK, but fter reched to optiml untity of complexing gent (8.0 mg (2.0 ml %0.4 (w/v) of MFPTAHK) there ws no chnge in the recovery yields. On this bsis, 8.0 mg of MFPTAHK ws dded to the solutions for ll subseuent works. Fig.2. Effect of MFPTAHK mount on the recoveries of nlyte ions (N: 3, smple ph: 6.5, smple volume: 50 ml) In order to desorb the retined metl MFPTAHK complex on Amberlite XAD 8 resin, the efficiency of the HCl nd HNO 3 solutions prepred in cetone nd wter were tested. The results were summrized in Tble 1. The cid solutions prepred in cetone hve higher recovery efficiencies compred to the cid solutions prepred in wter. Therefore 2.0 mol L 1 HNO 3 in cetone ws specified s the best eluent to desorb both nd ions complexes from the Amberlite XAD 8 resin. The effect of the volume of 2.0 mol L 1 HNO 3 in cetone, s eluting gent, ws lso investigted in the rnge of 2.5 15.0 ml. As seen from Fig. 3, the untittive recoveries were obtined fter 10.0 ml of the eluting gent, nd hence the optimum eluent volume ws specified s 10.0 ml for ll subseuent studies. The levels of nd ions in environmentl rel smples might be too low to be nlyzed directly. The increse in the rtio of smple volume to eluent volume contributes to obtin higher preconcentrtion fctor which provides convenience to detect the metl ions. For tht purpose the influences of the smple volume on the recoveries of nd ions were evluted in the rnge of 50-1000 ml contining 2.0 µg of Cd (II) nd 10.0 µg of ions under optimum conditions. The recovery vlues were found to be untittive until 100 ml of smple volume (Fig. 4). Hence, 100 ml ws chosen s the highest smple volume nd the preconcentrtion fctor ws clculted s 50 for the investigted metl ions t optiml conditions by the rtio of the highest smple volume (100 ml) nd the lowest finl volume (2.0 ml). 2205
Tble 1: The influences of eluent type on the recovery of nlyte ions (N: 3, smple ph: 6.5, eluent volume: 10 ml, untity of MFPTAHK: 8.0 mg). Eluent Type Recovery (%) 1.0 mol L 1 HCl in wter 46.3 ± 3.9 89.6 ± 4.1 1.0 mol L 1 HNO 3 in wter 57.4 ± 2.7 91.3 ± 2.5 2.0 mol L 1 HCl in wter 90.9 ± 1.6 92.8 ± 1.7 2.0 mol L 1 HNO 3 in wter 82.2 ± 3.1 93.9 ± 3.8 4.0 mol L 1 HCl in wter 71.1 ± 2.8 81.3 ± 2.1 4.0 mol L 1 HNO 3 in wter 86.8 ± 3.6 89.2 ± 2.7 1.0 mol L 1 HCl in cetone 59.7 ± 0.8 93.3 ± 3.1 1.0 mol L 1 HNO 3 in cetone 66.4 ± 2.5 95.2 ± 2.7 2.0 mol L 1 HCl in cetone 94.2 ± 3.1 96.3 ± 3.0 2.0 mol L 1 HNO 3 in cetone 95.3 ± 2.7 99.2 ± 4.2 4.0 mol L 1 HCl in cetone 79.3 ± 1.1 78.4 ± 1.9 4.0 mol L 1 HNO 3 in cetone 62.7 ± 2.5 67.2 ± 3.3 in the rnge of 50 500 mg L 1 were loded to the column filled with 250 mg Amberlite XAD 8, nd the dsorption mounts of nd ions onto resin were investigted. By using the obtined results, the Lngmuir isotherms were plotted (Fig. 5) nd the dsorption cpcity ( mx ) of the Amberlite XAD 8 resin for nd ions were clculted s 3.76 mg g 1 nd 5.07 mg g 1, respectively. Fig.4. Effect of smple volumes on the recoveries of nlyte ions (N: 3, smple ph: 6.5) Fig.3. The influences of eluent volume on the recovery of nlyte ions (N: 3, smple ph: 6.5, eluent: 2.0 mol L 1 HNO 3 in cetone, untity of MFPTAHK: 8.0 mg) Adsorption cpcity of the resin The plot of Lngmuir dsorption isotherm hs been commonly used to clculte the cpcity of the resins. Lngmuir isotherm model cn be fitted to dt in liner form by the eution given below 30 : C e e 1 = + (1) e C mx where e is the mount of metl dsorbed per unit weight of the resin (mg g 1 ) t euilibrium, C e is the euilibrium concentrtion of metl ions in solution (mg L 1 ), mx is the mximum dsorption in mono-lyered dsorption systems (mg g 1 ), nd L the dsorption euilibrium constnt relted to the dsorption energy (L mg 1 ). A stright line by plotting C e / e ginst C e exhibits liner reltionship, nd the Lngmuir constnts mx nd L cn be clculted from the slope nd intercept of the plot, respectively. In order to determine the Amberlite XAD 8 resin cpcity for the dsorption of nd ions, different concentrtions of ech metl ions L mx Fig.5. The plot of Lngmuir dsorption isotherm Effect of foreign ions on the recovery of nlyte ions The ccurte determintion of metl ions in different smple mtrix is freuently problemtic due to the presence of overwhelming interfering mtrix components. To this end, the model solutions contining fixed mounts of nd ions together with either individul mtrix ions or mixture of these ions were prepred nd the developed seprtion nd preconcentrtion procedure ws pplied to these solutions under optiml conditions. The experimentl results indicted tht the existence of mtrix ions hs no notble effect on the seprtion nd preconcentrtion of nd ions under the selected conditions (Tble 2). Conseuently, it cn be concluded tht the developed SPE method cn be pplied to the smples tht consist of vrious foreign ions t llowble levels. 2206
Tble 2: Influences of some foreign ions on the recoveries of nlyte ions (N: 3, smple ph: 6.5, untity of MFPTAHK: 8.0 mg). Ions Added s Conc.(mg L -1 ) Recovery (%) N + NCl 5000 90.3 ± 2.7 92.6 ± 4.1 K + KCl 500 90.8 ± 3.1 91.2 ± 3.3 C 2+ CCl 2 500 96.3 ± 2.7 96.9 ± 2.2 Mg 2+ Mg(NO 3 ) 2 1000 97.1 ± 2.5 90.3 ± 2.7 CO 3 N 2 CO 3 1000 96.4 ± 3.5 95.3 ± 4.6 SO 4 N 2 SO 4 1000 92.7 ± 4.4 90.8 ± 3.3 NH 4 + NH 4 NO 3 500 92.4 ± 2.2 91.9 ± 3.8 PO 4 3- N 3 PO 4 1000 93.4 ± 1.4 97.4 ± 1.1 Al 3+, Mn 2+, Ni 2+, Co 2+, Cu 2+, Zn 2+ * 25 90.5 ± 1.9 92.2 ± 3.1 Mixed 94.2 ± 2.5 91.2 ± 3.9 *Added s nitrte slts 5493 mg L -1 N +, 8390 mg L -1 Cl -, 2325 mg L -1 NO 3-, 250 mg L -1, K +, C 2+, Mg 2+, CO 3, SO 4, PO 4 3-, NH 4 +, 10 mg L -1 Al 3+, Mn 2+, Ni 2+, Co 2+, Cu 2+, Zn 2+ Tble 3: Spiked recoveries of nlyte ions from wter smples (N: 3, smple ph: 6.5, smple volume: 50 ml, finl volume: 2.0 ml). Added (µg) Se wter Strem wter Found (µg) Recovery (%) Found (µg) Recovery (%) 0.0 BDL* - BDL - 5.0 4.60 ± 0.11 92.0 4.71 ± 0.22 94.2 10.0 9.16 ± 0.27 91.6 9.47± 0.49 94.7 0.0 BDL - BDL - 20.0 18.01 ± 0.57 90.0 19.20 ± 0.44 96.0 40.0 36.94 ± 1.35 92.4 37.57 ± 1.18 93.9 *Below detection limit Tble 4: Spiked recoveries of nlyte ions from solid smples (N: 3, smple ph: 6.5, smple untities: 1.000 g of rice, crcked whet nd red lentil, finl volume: 2.0 ml). Added (µg) Rice Crcked whet Red lentil Found (µg) Recovery (%) Found (µg) Recovery (%) Found (µg) Recovery (%) 0.0 BDL - 0.11 ± 0.02 - BDL - 5.0 4.72 ± 0.23 94.4 4.85 ± 0.29 94.8 4.72 ± 0.37 94.4 10.0 9.60 ± 0.30 96.0 9.50 ± 0.39 93.9 9.59 ± 0.43 95.9 0.0 1.16 ± 0.12 - BDL - BDL - 20.0 19.86 ± 2.26 93.5 18.85 ± 1.32 94.2 18.51 ± 0.85 92.6 40.0 38.14 ± 1.57 92.4 38.12 ± 1.92 95.3 36.50 ± 1.97 91.2 Tble 5: Anlyte levels in rel solid/liuid smples fter being pplied the presented SPE procedure (N: 3, smple untities: 1.000 g of rice, crcked whet nd red lentil, finl volumes: 2.0 ml). Liuid smples (µg L 1 ) Solid smples (µg g 1 ) Se wter Strem wter (µg L -1 ) Rice (µg g -1 ) Crcked whet (µg g -1 ) Red lentil (µg g -1 ) 1.32 ± 0.11 1.44 ± 0.10 BDL 0.11 ± 0.02 BDL 5.56 ± 0.22 6.68 ± 0.18 1.16 ± 0.12 BDL BDL 2207
Tble 6: Comprtive dt from some recent studies on solid phse extrction. Anlytes SPE Adsorbent / Detection techniue PF LOD(µg L 1 ) RSD(%) ph Ref.,, Cu(II) Amberlite XAD 2/FAAS 50 0.8 23.2 <5 8.5 31, Chromosorb 106/ AAS 250 0.19 0.32 <7 9 32, Colloidl sulfur /FAAS 250 0.2 3.2 <5.5 8 33, MWCNTs/P2AT nnocomposite/aas 280 0.3 1.0 <3.5 6 34, Dowex Optipore V 493/FAAS 50 0.43 0.65 <5 2 35, Polyurethne fom/faas 37 0.80 3.75 <4.5 7.5 36, Amberlite XAD 8/FAAS 50 0.31 0.86 <4 6.5 Present work SPE: Solid Phse Extrction; PF: Preconcentrtion Fctor; LOD: Limit of Detection; RSD: Reltive Stndrd Devition Anlyticl figure of merits The precision of the method ws determined by repeting the method for 10 times by using model solutions contining 2.0 µg of nd 10.0 µg of ions under optiml conditions. Accordingly, the reltive stndrd devitions (RSD) for nd ions were found to be 3.7% nd 3.1%, respectively. The limit of detection (LOD) of the nlyte ions, defined s the concentrtion tht gives signl euivlent to three times the stndrd devition of 10 replicte mesurements of the blnk smples, ws found to be 0.31 µg L 1 nd 0.86 µg L 1, for nd ions, respectively. In order to check the ccurcy of the SPE method, different mounts of the nd ions were spiked in 50 ml of se nd strem wter s liuid smples, nd in 1.000 g of microwve digested rice, crcked whet nd red lentil s solid smples. As cn be seen in Tbles 3 nd 4, good recoveries were obtined for nd ions. The method ws pplied to determine the nlyte ions in rel smples fter being verified the ccurcy of the method (Tble 5). CONCLUSIONS The work in this disserttion investigted the use of solid phse extrction techniue in pre concentrtion nd seprtion of nd ions in the presence of MFPTAHK onto Amberlite XAD 8 resin in mini column. The procedure provides sensitive, sfe, rpid nd simple enrichment of nd ions in environmentl food nd wter smples prior to the determintion by FAAS with cceptble ccurcy nd precision. Vrious effective prmeters tht influence the preconcentrtion nd seprtion of Cd (II) nd Pb (II) ions were systemticlly studied nd optimized to give over 95% recovery yield nd the results obtined re discussed in this pper. The euilibrium dt of Cd (II) nd Pb (II) ions dsorption onto Amberlite XAD 8 resin were obtined with the Lngmuir isotherm eution nd the dsorption cpcity of the Amberlite XAD 8 resin, without ny lost of its physicl chemicl fetures nd dsorption properties, were evluted s 3.76 mg g 1 nd 5.07 mg g 1, respectively. The dt obtined from the proposed method hve been lso compred with the previously reported SPE methods 31-36 in terms of some optimiztion prmeters (Tble 6). 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