Analytica Chimica Acta 689 (2011) 5259

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Analytica Chimica Acta

journa l homepage: www.e lsev ier .co

Applica ymthe pre sefor the ns

Taher Ali eb

a Department ob Center of Exce

a r t i c l

Article history:Received 3 OcReceived in reAccepted 18 JaAvailable onlin

Keywords:Hg2+ imprinteElectrochemicCarbon paste electrodeUltratrace level

basedthe ress-linh meed wf theand odied.

mercury selective sensors, the proposed sensor was more selective, regarding the common potentialinterferer. This sensor showed a linear response range of 2.51095.0107 M and lower detectionlimit of 5.21010 M (S/N). The sensor was successfully applied to the determination of mercury in realsamples.

2011 Published by Elsevier B.V.

1. Introdu

Mercurybecause oftive solubilthe environous problemelement is atives tendthe gatheriin turn caunoia, excessloss, elevatMercury potion, injectidamage to t

Determihence greatlevels by matomic uotry and UV

CorresponE-mail add

0003-2670/$ doi:10.1016/j.ction

is one of the most toxic elements in the environment,its high reactivity, its extreme volatility and its rela-ity in water and living tissues [1]. Contamination ofment with mercury has unfortunately remained a seri-, despite noticeable efforts in recent years [24]. Thelso famous for the fact that ionicmercury and its deriva-to bioaccumulate in the human body which leads tong of high concentrations of the element, which canse symptoms such as weakness, sleeplessness, para-ive salivation, skin itching and swelling, fever, memoryed blood pressure, tremors, gingivitis, excitability etc.isoning can result from inhaling its vapor, its inges-on or absorption through the skin and does most of theheneurologic, gastrointestinal, and renal systems [58].nation of trace levels of mercury is of great urgency andefforts have beenmade to analyze the element in traceeans of a wide range of spectrometric methods such asrescence spectrometry, atomic absorption spectrome-spectrophotometry [912]. These techniques are cost

ding author. Tel.: +98 451 5514702; fax: +98 451 5514701.ress: alizadeh@uma.ac.ir (T. Alizadeh).

intensive, time consuming, hard to use and more importantly notsuitable for the task of in situ testing and monitoring. On the otherhand, electrochemical methods are the most favorable techniquesfor the determination of metal ions because of their high sensi-tivity in addition to low costs, ease of operation and portability.Stripping analyses of mercury have been reported by using differ-ent electrodes such as gold electrodes [13], iridium electrodes [14]and gold coated carbon electrodes [15].

In order to enhance the sensitivity and selectivity of the elec-trochemical determination of mercury, chemical modication ofelectrodes has received increasing attentions in the past decades.Numerous studies have been directed to the determination ofmercury(II) ion by modied electrodes. The modiers used haveincluded organic chelating groups [1623], polymers [2429], sil-icaandsolgel [3034], clays [3540]andclaysgraftedwithorganicchelating groups [41]. Most of the procedures, however, have faceddifculties achieving the sensitivity required for the determinationof low levels of mercury(II) ion in some real samples. Moreover,these materials do not provide a proper selectivity towards Hg2+

in the presence of some potential interferers like Cd2+, Pb2+, andCu2+. Therefore, there is still anurgentdemand for ahighly selectivemodier in this eld.

Molecular imprintedpolymers (MIP) arenewhigh selective syn-thetic receptors with molecular recognition sites designed for aparticular analyte.MIP technology has been developed as amethod

see front matter 2011 Published by Elsevier B.V.aca.2011.01.036tion of an Hg2+ selective imprinted polparation of a novel highly selective anddetermination of ultratrace mercury io

zadeha,, Mohamad Reza Ganjalib, Mashaalah Zarf Applied Chemistry, Faculty of Science, University of Mohaghegh Ardabili, Ardabil, Iranllence in Electrochemistry, Faculty of Chemistry, University of Tehran, Tehran, Iran

e i n f o

tober 2010vised form 1 January 2011nuary 2011e 25 January 2011

d polymeral sensor

a b s t r a c t

A simple and very selective electrode,for the determination of Hg2+ ions increated in the vinyl pyridine based croand polymer powder were mixed witthe responses of the electrodes modiperformance of the recognition sites oselective electrode, were investigatedresponse of the electrode was also stum/locate /aca

er as a new modifying agent fornsitive electrochemical sensor

on amercury ion imprinted polymer (IIP), and its applicational samples is introduced. Mercury ion selective cavities wereked polymer. In order to fabricate the sensor carbon particleslted n-eicosane. An explicit difference was observed betweenith IIP and non imprinted polymer (NIP), indicating properIIP. Various factors, known to affect the response behavior ofptimized. The interference of different ionic species with theThe results revealed that, compared to previously developed

T. Alizadeh et al. / Analytica Chimica Acta 689 (2011) 5259 53

for the preparation of synthetic receptors by polymerization ofself assembled complexes, formed by functional monomers and atemplate in the pre-polymerizationmixture [4248]. This technol-ogy can also be used for the preparation of polymers containinginorganic cpolymers (have so far[5356].

Recentlyapplicationchemical sefor differenselectivity omaterials tfying agentto the highinterestinga novelHg2

As mentionviously usesuffered froagents provthe responstion capaciAlthough, pvide considon the ion econsiderabled with Hgof the previeven moretion capacithigh sensitishow a higronments. Ipolymers bifying agentcarbon pastmodiedwdeterminat

In this wsized basedpolymer wpowder inpare a Hg2+

showed ver

2. Experim

2.1. Instrum

Electroctem using acarbon pastmer (NIP) wan Ag/AgCltrodes, resp

Vinyl pyunder redu(SigmaAldpresence of2,2-(2-MetGeel, Belgiuwere fromgrade and w

2.2. Preparation of Hg(II) imprinted polymer and modiedelectrode

In order to prepare IIP, 1mmol Hg(NO3)2 and 4mmol 4-vinylewe-azoL DM2 gabathwashinallyt 60

e oflectr

epar

conenizuentndhemeltal pin deC. Aftal wde caurfacde su

eterm

prepHg2

d intlutioal cetentidiffe.

ults

ercur

eralof med Iiazoneglyin thN-M

mplemoninkintholecenfor Hcomrmalhylena poll offor

ationation selective sites as the so-called ion imprintedIIP) [4952]. Different kinds of imprinted polymersbeen reported for the recognition of mercury ions

, we have reported several papers describing theofMIP particles as a recognition element of the electro-nsors such as voltammetric and potentiometric sensorst kinds of molecular analytes [5760]. Due to the highf these materials, the electrode containing imprinted

ends to show selective behaviors. Besides, this modi-can pre-concentrate the analyte in the electrode dueadsorption capacity of these materials. The obtainedresults from the previous works provoked us to design+ electrochemical sensor, using ion imprinted polymers.ed before, each of the described modifying agents, pre-d in Hg2+ electrodes, possessed some advantages andmsomeshortcommings. For example, organic chelatingide amoderate selectivity, but suffer from instability ine. Zeolite andsolgelsprovidehighstability andadsorp-ty, while suffering from an inherently low selectivity.olymeric materials like peruorinated polymers pro-erably lower detection limit [28], they function basedxchanging mechanism and their selectivity is thus note. On the other hand, it seems that the electrodesmodi-2+ IIP possesses approximately the advantages of mostously stated modifying agents. IIP has a high selectivitythan organic chelating agents. It provides high adsorp-ies comparable with that of clays and zeolite, providingvity and lowerdetection limit. Also, IIPmaterialsusuallyh stability and durability against harsh chemical envi-n other words, electrodes modied with ion imprintedring together the advantages of different kinds of mod-s in a single modied electrode. Moreover, both IIP ande are cheapmaterials and thus a carbon paste electrodeith IIP can provide an efcient and cheap sensor forHg2+

ion.ork, the Hg2+ selective imprinted polymer was synthe-on a new formulation. The obtained Hg2+ imprinted

as used as a modifying agent and mixed with carbonthe presence of melted n-eicosane in order to pre-selective voltammetric sensor. The prepared electrodey interesting analytical characteristics.

ental

ent and reagents

hemical data were obtained with a three-electrode sys-PGSTAT302 Metrohm potentioastat/galvanostat. The

e electrodes modied with IIP or non imprinted poly-ere used as a working electrode. A platinum wire andelectrode were used as the counter and reference elec-ectively.ridine (Merck, Germany) was puried by distillationced pressure. Ethylene glycol dimethacrylate (EDMA)rich, USA), was distilled under reduced pressure in thehydroquinone inhibitor and stored at 4 C until use.

hyl propionitrile) was obtained from Acros Organic,m. Dimethyl sulfoxide (DMSO) and Hg(NO3)24H2OMerck, Germany. Other chemicals were of analyticalere purchased from Merck, Germany.

pyridintor (2,2in 3mwith Nwaterrstlytion. Fdried aabsencpaste e

2.3. Pr

ForhomogSubseqbath, ato theThe n3mmat 45

materielectrotrode selectro

2.4. D

Theing theinsertethis sochemicpre-pothen ato 0.3V

3. Res

3.1. M

Sevrationpreparride, dethyleworkappliedand coas thecross-l2-naph[55]. Rlationbinaryits theand etanol as

In aappliedpreparredissolved in20mLofDMSO. Then, 0.15 gof the initia-bisisobutyronitrile) andcross-linker (EDMA), dissolvedSO, was mixed with the previous solution and purgeds for 10min. The polymerization was carried out in aat 70 C for 24h. The obtained polymer particles wereedwith ethanol and thenwashedwith a 0.1MHCl solu-, the particles were washed with distilled water andC. TheNIPwas prepared, using the same protocol in theHg(II). The prepared IIP and NIP were used for carbonode fabrication.

ation of the sensors

struction of the sensor (IIP-CP), 0.02 g graphite wased in a mortar with 0.005g of powdered IIP for 10min.ly, n-eicosane, 0.007g was melted in a dish in a wateratedat4550 C. Thegraphite/IIPblendwas thenaddeded n-eicosane and mixed with a stainless steel spatula.aste was used to ll a hole (2.00mm in diameter andpth) at the end of an electrode body, previously heateder cooling at room temperature, the excess of solidiedas removed with the aid of a sheet of paper sheet. Then be reused after each experiment by moving the elec-e on a paper sheet in order to rub out a thin layer of therface.

ination procedure

ared electrode was inserted into the solutions contain-+ (pH=2.5) while being stirred. Then, the electrode waso thewashing solution (water-neutral pH), remaining inn for 15 s. The electrodewasnally placed in the electro-ll containing 10mL of HCl (0.12M). At rst, a negativeal of 1.2V was applied to the electrode for 30 s andrential pulse voltammetry was performed from 0.10

and discussion

y ion imprinted polymer

formulations have already been reported for prepa-ercury ion imprinted polymers. Liu et al. [56] haveIP for mercury by copolymerizing mercury chlo-aminobenzene (DAAB) and vinylpyridine (VP) usingcoldimethacrylate (EGDMA) as a cross-linker. Anotheris eld is from Denizli and his coworkers [53] whoethacryloyl-(l)-cysteine as both a functionalmonomerxing agent. Copolymerization of the methacrylic acidomer, and trimethylolpropane trimethacrylate as theg agent, in the presence of Hg(II)-1-(2-thiazolylazo)-complex is another method reported by Dakova et al.tly, Singh andMishra [54] have described a new formu-g(II)-ion-imprinted polymer (IIP) by the formation of aplex of mercury with 4-(2-thiazolylazo) resorcinol andcopolymerization with methacrylic acid (monomer)e glycol dimethadrylate (crosslinker), and in cyclohex-rogen.the described procedures an additional ligand has beenpreparing IIPs, which increases the complexity of themethod. In the present work, however, we applied a

54 T. Alizadeh et al. / Analytica Chimica Acta 689 (2011) 5259

rcury ion imprinted polymer synthesis.

new and simer. Accordas both themercury ionof 4:1 (monization starshows thePrimary evathe polyme

3.2. Compa

The carban Hg2+ sostirred. Theandanegatithe differendeterminatin the casement, the IIsolution forobtained voshown in FiCP electrodindicating tcavities inof the electdecreased badsorbed iorate in theThis can beions are locstrongly anHg2+ adsorp

ectivonseponssed bte anFig. 1. Schematic representation of the method applied for me

mple method for preparing mercury imprinted poly-ing to themethod of currentwork, vinyl pyridine actedfunctional monomer and complexing agent. This way,s simply interacted with vinyl pyridine in a mole ratioomer/cation) in dimethyl sulfoxide. Then, the polymer-

nonselits respthe resdecreagraphited in the presence of the initiator. Fig. 1 schematicallyroute for preparing IIP according to the current work.luation of the obtained IIP showed a high capability ofr for adsorption of Hg2+ in comparison to NIP.

rison of the IIP-CP electrode with NIP-CP electrode

on paste electrode modied with IIP was incubated inlution, and meanwhile the solution was continuouslyn, the electrodewas inserted in the electrochemical cellvepotentialwasapplied to theelectrode. Subsequently,tial pulse voltammetry technique was applied for theion of mercury. The same experiment was carried outof the electrode modied with NIP. In another experi-P-CP and NIP-CP electrodes were inserted in a washing10 s, after being removed from the Hg2+ solution. Theltammetric signals of the twomentioned electrodes areg. 2. It can be seen that the signal obtained for the IIP-e is noticeably higher than that of the NIP-CP electrode,he existence and proper functioning of the selectivethe IIP, created in the polymerization step. Washingrodes, after removing them from the analyte solution,oth electrode signals indicating removing of weaklyns on the IIP or NIP surface sites. However, the decreaseNIP signal is higher than that in the IIP-CP electrode.related to the fact that most of the adsorbed mercuryated in the selective sites of the IIP that are attractedd specically to the IIP, while the sites responsible fortion in the NIP are surface adsorption sites of weak and

Fig. 2. Compaand NIP-CP elmetry conditioE-pulse =0.1Ve nature. The initial response of CP electrode as well asafterwashing is also represented in Fig. 2. It is clear thate of CP electrode for Hg2+ is small and it is considerablyy applyingwashing step, indicating lower afnity of thed binder for Hg2+, compared to NIP and especially IIP.rison of differential pulse voltammetry responses of IIP-CP electrodeectrodes with and without washing step; anodic stripping voltam-ns: E-conditioning=1.2V, conditioning time=30 s, E-step=0.01V,, pulse time=0.01 s, and scan rate =0.1V s1.

T. Alizadeh et al. / Analytica Chimica Acta 689 (2011) 5259 55

Fig. 3. Evalua 7) (I),tion time=20 ing=time=0.01 s, a

3.3. Evalua

As descrhave been icury ions, bBi3+, Pb2+, Feld. The in(a) the interily reducedand Pb2+. Tods compriapplicationmain interfcury due toeffects causinteract witused for moferes inuedeposition

The selethe describ1 and 2) anobtained votion of 11As it is cleatimes as mued electroHg2+ a clearing in compworks in thnals observranges thatmeaning thof Hg even a

3.4. The efferesponse for

In orderferent amou

hangdetesion.on aelecinat). It isearsthe ssitesa threed seelectefferepae paobtahe ceicostion of selectivity of developed sensor; responses of the electrode for Hg2+ (110min, stirring rate =700 rpm; anodic stripping voltammetry conditions: E-conditionnd scan rate =0.1V s .

tion the selectivity of the sensor

ibed in Section 1, numerous kinds of modifying agentsntroduced for the selective pre-concentration of mer-ut the interference effect of some cations such as Cu2+,e3+, Ag+, Au3+ and Cd2+ is still the main problem in theterference effect can be categorized into two sections:ference effects caused by themetal ions which are eas-to themetallic state such as: Au3+, Ag+, Pt4+, pd2+, Cu2+

hese ions show their interference effect in the meth-sing the pre-concentration step, performed through theof reduction potentials. These ions are yet known as theering ions in the voltammetric determination of mer-the possible co-deposition [37,61]. (b) The interferenceed by the metal ions such as Cd2+, Bi3+, Ag+ which canh thiol groups, included mainly in the chelating agentdifying the mercury selective electrodes. These inter-nce the determination of mercury even in open circuitof mercury on the electrode [23,41].

were cmetricconcluof carbricateddetermFig. 4(Isor appIIP arenitionabovepreparof the

Theof the pof thesing theFrom tand n-ctivity of the method against two representatives ofed potential interfering groups including Cu2+ (groupd Cd2+ (group 1) were investigated. Fig. 3 shows theltammetric signals of the target ion in the concentra-07 M and Cu2+ and Cd2+ at different concentrations.r, when the concentrations of both Cd and Cu are 100ch as that of Hg2+ no signal is shown by the IIP modi-de. At Cd2+ concentration 500 times as much as that ofsignal appears for Cd2+. These results are very interest-arison to the selectivity results of previously reportede case of these cations. It must be noticed that the sig-ed for these cations in the electrode are in the potentialare far enough from the Hg potential, approximatelyat these ions have no interference in the determinationt higher concentrations of the described interferer ions.

ct of the electrode composition on the MIP-CPHg2+

to nd thebest composition for the IIP-CP electrode, dif-nts of ingredients including IIP, carbon and n-eicosane

n-eicosanecontent of tthe electrocontent incTherst incof electronence of highdecreased wthe fact thathe IIP on th

It is alsofor IIP-CP ebinder (n-eelectrode rconductivit

3.5. Washin

As descthe removaface. This cCu2+ (II) and Cd2+ (III); (a) 1104, (b) 5105, (c) 1105; extrac-1.2V, conditioning time=30 s, E-step=0.01V, E-pulse =0.1V, pulse

ed in the xed conditions of extraction and voltam-rmination and the obtained responses were used forThe IIP-CP electrodewas preparedwith a xed amountnd n-eicosane and different amounts of IIP. The fab-trode, in each case, was used for the extraction andion of Hg2+. The obtained results are presented inclear that themaximumresponse for theprepared sen-in the IIP amount of 0.005g. The higher the amounts ofensor response increases due to providing more recog-on the electrode surface. However, increasing the IIPshold amount, leads to a decrease in the response of thensor,most probably due to decrease in the conductivityrode surface.ct of amounts of carbon and n-eicosane on the responsered electrodewas investigated by varying the amountsrameters in the IIP-CP electrode, followed by record-ined signal. The results are shown in Fig. 4(II) and (III).orresponding curves, the optimum amount of carbonane were found to be, 0.02 and 0.007g for carbon and

amounts, respectively. Initially, increasing the carbonhe IIP-CP electrode was found to lead to an increase inde response, but, after a denite point, further carbonreasing resulted in lowering the corresponding signal.rease in the response canbe related to the enhancementtransferring capability of the electrode in the pres-er carbon content. Furthermore, the electrode responseith increasing the carbon content, can be attributed to

t the more carbon leads to a decrease in the content ofe electrode surface.clear that an optimumamount of n-eicosane is requiredlectrode preparation. Presence of higher amounts of theicosane) in the IIP-CP electrode leads to a decrease inesponse, because of decreasing the electrode surfacey.

g effect

ribed previously, washing of the electrode results inl of weakly adsorbed species from the electrode sur-an be used for improving the sensor selectivity and

56 T. Alizadeh et al. / Analytica Chimica Acta 689 (2011) 5259

omitting thapplied.

It was fothis aim. Indecreased,was not conmethanol, ain water) anaimed signa

The optisolution wabetween thafterwardschosen as o

3.6. The efferesponse

In orderpared electtimes. Nextlowed by dshown in Fitime leads tin the electthe responstime, the 15

The pHeffect on thFig. 4. Evaluation of the effect of electrode compositi

e interference effects, if proper washing conditions are

und that pure water is a proper washing solvent forthis washingmedia the NIP-CP signal was considerablywhile the IIP-CP signal decrease as a result of washingsiderable. Different organic solvents such as ethanol,cetone and acetonitrile were added to the water (2%d tested as the washing solution. No improvement forl from the mentioned mixtures was observed.mum time of immersing the electrode in the washings also investigated. It was found that the differencee response of IIP-CP and NIP-CP increased till 15 s andthe signal reached to partly steady state. Thus, 15 s wasptimal washing time.

ct of Hg2+ extraction conditions on the electrode

to nd the optimumelectrode incubation time, the pre-rodes were inserted into the Hg2+ solutions for various, the electrode was removed from the solutions, fol-ifferential pulse voltammetry. The obtained results areg. 5(I). According to this gure, increasing the extractiono an intensive increase in the extraction of mercury ionrode till about 15min. After this period, the increase ine is not considerable. In order to decrease the analysismin was selected for the extraction time.of the extraction solution was also checked and itse Hg2+ extraction in the electrode was studied. For this

purpose, thvarious pHstant stirrinremoved frelectrochemFig. 5(II). Awork. The o2.5. Decreasignal due tinto the elenitrogen minteractionselective sitable decreabecause ofments at hi

In orderwas extractrates, wherconstant. Thmetric elecpresented ithe highererable effecIIP-CP electincreasing tther increasthe amounchosen as oon on its response.

e prepared electrode was inserted into solutions withvalues where they were incubated for 10min at a con-g rate. After the mentioned time, the electrode wasom the solution and immersed into the solution of theical cell. The results of this experiment are shown in

s can be seen, stabilizing the pH is crucial task in thisptimum pH for the proposed method was found to besing of the pH, lower than 2.5, decreases the electrodeo the decrease in the amount of the target ion extractedctrode. This is probably because of the protonation ofoieties of the selective sites of the IIP, that weaken theof Hg2+ with the vinyl pyridine groups, existing in thees of the IIP. At higher pH values (above 2.5) a consider-se in the electrode signal can be distinguished probablytendency of Hg2+ ions to precipitate as hydroxide sedi-gher pH values.to optimize the stirring rate and extraction period, Hg2+

ed in the prepared IIP-CP electrodes at various stirringeas the other extraction parameters were the same andeobtained results, showing the variationof the voltam-trode signal to mercury against the stirring rates, aren Fig. 5(III). As can be seen, the greater the stirring rate,the electrode response for Hg2+, indicating the consid-t of the stirring rate on the Hg2+ extraction into therode. The growth in the voltammetric response withhe stirring ratecontinues up to 500 rpm. However, fur-ing of the stirring rate does not considerably inuencet extracted. Therefore, a stirring rate of 500 rpm wasptima for this variation.

T. Alizadeh et al. / Analytica Chimica Acta 689 (2011) 5259 57

3.7. The effedeterminati

After accopen circuithe electrodthe electrolout in ordeelectrode retask for obdifferent eleanalysis, weIt is clear ththe responsamplitude,that HCl (0amplitude a

3.8. Analyti

After thtion methodspecies wasmaximumerror of 5%developedalkaline and1000-fold eFig. 5. Evaluation of the extraction conditions effects on the electrode response.

ct of pH and electrolyte type of electrochemicalon

umulation of mercury ions on the electrode surface att condition and its washing with the washing solution,e was inserted into an electrochemical cell, containingyte solution with various pH values. This was carriedr to investigate the effect of the electrolyte pH on thesponse. It was found that the acidity of pH is crucialtaining strong and stable signals. Next, the effects ofctrolytes, providing acidic media for the voltammetricre tested. The obtained results are illustrated in Fig. 6.at the type of the electrolyte considerably inuencese behavior of the electrode, with respect to the signalbackground current and potential shift. It can be seen.12M) leads to better results, in terms of higher signalnd lower background current.

cal characterization

e optimization and establishment of the determina-for the prepared IIP-CP sensor, interference of variousexamined. The tolerance limit was established as the

concentration of foreign species that caused a relativein the analytical signal. For 50nM of mercury(II), thesensor was not affected by the presence of differentearth alkaline cations even in concentrations having

xcess to the Hg2+. Fig. 6. Effect of different electrolyte on the sensor response to Hg2+.

58 T. Alizadeh et al. / Analytica Chimica Acta 689 (2011) 5259

Table 1Determination of Hg(II) in water samples containing 0.025M Hg2+ (adjusted by spiking).

Sample IIP-CP Reference method

R 2+

Tap water 2River water 3Lake water ( 3

Fig. 7. Calibraconditions; ins

A vast minterfere inNi(II), Cu(II)as that of th(within thenal. Only Cdconcentrati

The ressor towardcalibrationshowed a lof 2.510(S/N=3). Eareplications

3.9. Determ

Determiples. The saoptimized sfree. 50mLnal conceadjusted tostep by stepopedsensorrecoveries asorhasapromercury inwas also teslyzed by difmercury vamethod [62tistically wisignicant d

dicaque fs.

clus

newtracagenrcuryto shcteda preion li

nces

Wientoxico. Ullri01) 24. Fitzg. Doeb. Patn760. Crinnatoh,.O. ReiTotalCapel. RubahmaHg2+ found (M) Recovery (%)

0.024 96.0(garasou, ardabil) 0.026 104.0shoorabil, ardabil) 0.027 108.0

tion curve of the developed mercury ion sensor in the optimizedet in the linear range of the calibration curve.

ajority of metal ions were found not to signicantlythe detection of Hg(II) including Cr(III), Mn(II), Co(II),, Zn(II) or Pb(II), at a concentration 400 times as muche target analyte, giving rise to no signicant variationsstandard deviation of the method) in the Hg(II) sig-2+ was found to show some degree of interference at

95%, intechnisample

4. Con

Theions atifyingfor mefoundtrode arole ofdetect

Refere

[1] J.G.Eco

[2] S.M(20

[3] W.F[4] I.W[5] P.B

757[6] W.J[7] H. S[8] S.B

Sci.[9] J.L.

[10] A.M[11] L. Ron 200-fold excess to that of Hg(II).ponse of the prepared and optimized IIP-CP sen-s Hg2+ concentration variations was checked. Thegraph (shown in Fig. 7) of the prepared sensorinear relationship in Hg concentration in the range95.0106 M with a detection limit of 5.21010 Mch point of the calibration graph is the average of three.

ination of Hg2+ in real samples

nation ofmercury(II) was carried out in real water sam-mples were tested before addition of mercury(II) withensor and itwas found that all of themweremercury(II)of samples were then spiked with mercury(II) till thentration reached 0.025M. the pH of solutions was2.5. The determination method was then performed, according to the proposed procedure, using the devel-. The results canbeseen inTable1. Theobtainedpercentnd corresponding standard errors indicate that the sen-per capability for accurateandprecisedeterminationofreal samples. The signicance of the developedmethodted. For this aim the previous samples were again ana-ferential pulse stripping voltammetry after sorption ofpor on gold-plated electrode as the selected reference]. The results (shown in Table 1) were compared sta-th those of the newly developed sensor. There was noifference between these results at condence level of

[12] M.S. Jeou[13] C.M. Wat

(1999) 31[14] M.A. Nola[15] L.A. Khus[16] H.M.J. Lui[17] G.R. Mora

17 (2005[18] W. Huang[19] L.P. Singh[20] V.K. Gupt[21] W. Yanta[22] J. Wang, M[23] F. Wanga[24] U. Tamer[25] H. Zejli, P

68 (2005[26] A.A. Khan[27] K.C. Chen[28] P. Ugo, L.[29] P. Ugo, L.[30] G.C. Carra[31] A. Dome

166116[32] A. Walca

414421[33] A. Walcar[34] Y. Guo, A[35] Z. Navrat[36] I.G. Svegl[37] P. Kula, Z

91101.[38] Z. Navrat[39] G. Raber,

163193[40] I.G. Svegl

358362SD% (n=5) Hg found (M) RSD% (n=3)

.31 0.022 6.6

.70 0.027 5.9

.9 0.029 6.9

ting the signicance and applicability of the developedor reliable determination of trace amount Hg2+ in real

ion

electrochemical sensor for determination of mercurye levels based on the application of IIP as a novel mod-t in the carbon paste electrode showed high selectivityin the presence of common potential interferers was

ow satisfactory results. The IIP in the carbon paste elec-as the selectivity inducing agent and also played the-concentrator to exhibit high selectivity as well as lowmit.

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Application of an Hg2+ selective imprinted polymer as a new modifying agent for the preparation of a novel highly selectiv...IntroductionExperimentalInstrument and reagentsPreparation of Hg(II) imprinted polymer and modified electrodePreparation of the sensorsDetermination procedure

Results and discussionMercury ion imprinted polymerComparison of the IIP-CP electrode with NIP-CP electrodeEvaluation the selectivity of the sensorThe effect of the electrode composition on the MIP-CP response for Hg2+Washing effectThe effect of Hg2+ extraction conditions on the electrode responseThe effect of pH and electrolyte type of electrochemical determinationAnalytical characterizationDetermination of Hg2+ in real samples

ConclusionReferences