Available online at www.sciencedirect.com

Sensors and Actuators B 127 (2007) 362369

Determination of paracetamol based on elecencSahhemi

March007

Abstract

Preparatio roperfilm was pre senctemplate mo e pewas evaluate etersand optimiz sitivipeak curren n atdemonstrate lationwas smaller .5 m7.9 107 M (S/N = 3). Molecularly imprinted polypyrrole modified pencil graphite electrode showed a stable and reproducible response withoutany influence of interferents commonly existing in pharmaceutical samples. 2007 Elsevier B.V. All rights reserved.

Keywords: Molecularly imprinted polymer; Polypyrrole; Pencil graphite electrode; Electropolymerization; Paracetamol

1. Introdu

Paracetaanalgesic awas firstlyby Von Mehome medeffective trchildren. Itin many co[2].

Over the(MIPs) havin sensor dserious potral receptocost and e

CorresponE-mail ad

0925-4005/$doi:10.1016/jction

mol (N-acetyl-p-aminophenol) is a commonly usednd antipyretic drug these days [1]. Paracetamol (PC)introduced into medicine as an antipyretic/analgesicring in 1893 and has been in use as an analgesic forication for over 30 years and is accepted as a veryeatment for the relief of pain and fever in adults andis the most used medicine after acetylsalicylic aciduntries as an alternative to aspirin and phenacetin

past two decades, molecularly imprinted polymerse attracted broad interest from scientists engagedevelopment. This attention can be explained by theential advantages of using MIPs in place of natu-rs and enzymes such as their superior stability, lowasy preparation. The general principal of molecu-

ding author. Tel.: +90 222 3350580; fax: +90 222 3204910.dress: ysahin@anadolu.edu.tr (Y. Sahin).

lar imprinting is based on such a process where functionaland cross-linking monomers are copolymerized in the pres-ence of a target analyte (the imprint molecule) which acts asa molecular template. This procedure can be accomplished viaeither reversible covalent bonding or non-covalent interactionsbetween monomers and imprint molecules. Other preparationmethods of molecular imprinting polymers (MIPs) have beenreported including chemical grafting, soft lithography technique[3], molecular self-assembled approach [4] and electropoly-merization [3]. These films can be synthesized in situ at anelectrode surface by electropolymerization technique. This tech-nique has some attractive features including the easy adherenceof the polymeric films to the surface of conducting electrodesof any shape and size and the ability to control thicknessof the films under different deposition conditions [5]. Vari-ous types of electrosynthesized polymers based on molecularimprinting have been reported in the literature including poly(o-phenylenediamine) [5], polyphenol [6], polypyrrole [7] andcopolymer of aniline with o-phenylenediamine [8].

Molecular imprinting has been approached using the elec-trosynthesis of conducting polymers through galvanostatic,

see front matter 2007 Elsevier B.V. All rights reserved..snb.2007.04.034imprinted polypyrrole modified pLevent Ozcan, Yucel

Anadolu University, Faculty of Science, Department of CReceived 28 December 2006; received in revised form 21

Available online 4 May 2

n of a molecularly imprinted polymer (MIP) film and its recognition ppared by the cyclic voltammetric deposition of pyrrole (Py) in the prelecule (paracetamol) through on a pencil graphite electrode (PGE). Thd by differential pulse voltammetry (DPV). Several important param

ed. The molecularly imprinted film exhibited a high selectivity and sent observed for paracetamol oxidation versus paracetamol concentratios linearity over a concentration range of 5M to 0.50 mM with a correthan the first regions slope with a wide concentration range of 1.254tropolymerized-molecularlyil graphite electrodein stry, 26470 Eskisehir, Turkey

2007; accepted 20 April 2007

ty for paracetamol are investigated. The polypyrrole (PPy)e of a supporting electrolyte (LiClO4) with and without arformance of the imprinted and non-imprinted (NIP) filmscontrolling the performance of the PPy was investigatedty toward paracetamol. The calibration curve for the DPVMIP electrode shows two linear regions. The first regioncoefficient of 0.996. The slope of the second linear region

M (R2 = 0.990). The detection limit (3) of paracetamol is

L. Ozcan, Y. Sahin / Sensors and Actuators B 127 (2007) 362369 363

potentiostatic and cyclic voltammetric methods. These methodsprovide a simple and rapid technique of controlling the thicknessof the condof any sizin the desiinclude pyof neutralby electropadvantageimmobilizanition filmto coat an efilm. Thelated by poand Freundsaccharide-involves thacid complmerizationThe formatrochemicathe incorppolymer. Mrescein, rhowere electrous solutioand in thethe MIP-ctemplate mcaffeine-imtatic electrone of thethe presencin the matquent washrecognizingimprintedpyrrole ontplate, in ordevice [12]

The useparacetamoing electrowork. Paraof its populthe determitablets and

2. Experim

2.1. Chem

Paraceta(98%), lnol (>99.5%Fluka (Stei(>99.5%, M

phosphate (98.5%, SigmaAldrich, Steinheim, Germany),lithium perchlorate (98%, Lancaster, Morecambe, England)

her red weim,

coldar

solu(Sar), V

l, DuSmiurchf pay.

ppar

ctrocT 1

re (Eas us

as threme

cheyed fomat 11a C

nd)luenateC.unds

repa

okite letactthee tothe esolufacege b00 m

andocessurfal tem

ionedpoterovidinedover

de (nuctive polymer film grown adherent to a transducere and shape. The monomers that have been usedgn of molecularly imprinted conducting polymersrrole, aniline and o-phenylenediamine. Imprintingcompound-glucose has been achieved successfullyolymerization of o-phenylenediamine [5]. The bigof electropolymerization in comparison with othertion techniques lies in the ability to deposit a recog-at precise spot of the detector surface. It is possiblelectrode with complex geometry with homogeneouspolymer thickness and deposition density is regu-lymerization conditions (e.g., applied voltage). Deore

reported a new approach for the electrosynthesis ofimprinted poly(aniline boronic acid) [9]. The methode formation of a saccharideaminophenylboronic

ex in the presence of fluoride to allow the electropoly-of a self-doped, molecularly imprinted polyaniline.

tion of the anionic monomer complex enables elec-l polymerization at near neutral pH (57) ensuringoration of saccharide in the resulting, self-doped

olecularly imprinted polymers selective for fluo-damine or 2,4-dichlorophenoxyacetic acid (2,4-D)

opolymerized onto graphite electrodes using an aque-n equimolar in resorsinol/ortho-phenylenediaminepresence of the template molecule. For the dyes,

oated electrodes showed higher affinity for theirolecule than for a non-template dye [10]. Theprinted polymer was synthesized using galvanos-

opolymerization of pyrrole monomer directly ontogold electrodes of a 9 MHz AT-cut quartz crystal ine of caffeine. Caffeine molecules were entrapped

rix of polymer film, and were removed by subse-ing with water, leaving behind pores capable ofthe target analyte molecule [11]. A molecularly

polymer was prepared by electropolymerization ofo a stainless steel frit, using ochratoxin A as the tem-der to make a micro solid phase preconcentration.

of a differential pulse voltammetry to determine thel using pencil graphite electrode prepared by imprint-

polymerization was reported for the first time in thiscetamol was chosen as template molecule becausearity and electroactivity. Its successful application tonation of paracetamol in commercial pharmaceuticalsyrup has been demonstrated.

ental

icals and reagents

mol (98%), dopamine (98.5%), phenacetin-ascorbic acid (>99.5%), d-glucose (>99.5%), phe-

), potassium chloride (99%) were obtained fromnheim, Germany). Potassium dihydrogen phosphate

erck, Darmstat, Germany), potassium hydrogen

and otand usSteinhuntil agen inbufferwaterTurkey(Nobe(Glaxowere ptions ostabilit

2.2. A

ElePGSTAsoftwatem w(PGE)measu

IONemplo

ChrAgilenpump,ScotlaThe eflow rat 25 compo

2.3. P

A Ngraphical conwire totonitrilbeforeizationthe surtial ranrate: 1pyrroletion prgive aoriginaconditusingcess pdetermby uncelectroeagents commercially available as analytical gradeithout further purification. Pyrrole (98%, Aldrich,Germany) was distilled repeatedly under vacuumorless liquid was obtained and kept under nitro-kness at 4 C. Stock solutions of paracetamol andtions were prepared by using ultra-pure deionizedtorius). Minoset and MinosetPlus (Roche, Kocaeli,ermidon (Ilsan Iltas, Kocaeli, Turkey), TylolHotzce, Turkey) paracetamol tablets and Calpol syrupthKline, Abdi Ibrahim Ilac A.S., Istanbul, Turkey)ased from local pharmacy. Freshly prepared solu-

racetamol were prepared each day owing to its low

atus

hemical studies were performed using Autolab00 potentiostat-galvanostat controlled by a GPES 4.9cochemie, The Netherlands). Three electrode sys-

ed for all measurements; a pencil graphite electrodee working electrode and a Pt auxiliary electrode. Allnts carried out with an Ag/AgCl reference electrode.ck45 model (Radiometer, France) pH-Ion meter wasor pH measurements.tographic measurements were carried out using a00 Series HPLC (Germany) consisting of a gradient18 separator column (ACE, 5m, 150 4.6 mm,coupled with an UVVis detector and computer.t used was methanol:water (80:20) mixture at aof 0.8 mL min1. All separation was carried outThe detection was performed at 254 nm for the.

ration of MIP and NIP electrodes

pencil model 2000 (Japan) was used as a holder forads (Tombo, HB, 0.5 mm diameter, Japan). Electri-with the lead was obtained by soldering a metallic

metallic part. PGEs were washed with water and ace-remove the impurity and dried at room temperaturexperiments. Then, PGE was immersed the polymer-tion. The MIP was obtained by electrodeposition onof the PGE using cyclic voltammetry in the poten-etween 0.60 and +0.80 V during four cycles (scanV/s) in aqueous solution of 0.1 M LiClO4, 0.05 M0.020 M paracetamol. After the electropolymeriza-

s, the embedded paracetamol were then extracted toce complimentary in shape and functionality to theplate paracetamol. Then the imprinted polymer wasin 0.1 M KCl + 0.05 M phosphate buffer solution

ntial cycling between 0.6 and +1.00 V. This pro-ed to remove the template inside the polymer. Wethe excess paracetamol in this solution using DPVed PGE (the data were not given here). A controlon-imprinted polymer modified electrode, NIP) was

364 L. Ozcan, Y. Sahin / Sensors and Actuators B 127 (2007) 362369

prepared in every case under the same experimental condutionsbut without adding the paracetamol, to check the reliability ofthe measurements.

2.4. Electroanalytical measurements

Differential pulse voltammetric measurements were carriedout in a three-electrode cell, in 0.1 M KCl + 0.05 M phos-phate buffer at pH 7.0. Before the measurements, electrolyticsolutions were purged with nitrogen for 5 min. Current mea-surements were performed using differential pulse voltammetry(DPV) in the potential range between 0.00 and 0.80 V. Torecord differential pulse voltammograms, the following instru-mental parameters were used: step potential 8 mV, modulationamplitude 50 mV; scan rate 15 mV/s. All electroanalytical mea-surement were made at room temperature.

2.5. Sample preparation

Various commercial pharmaceutical tablets and syrup havingparacetamotablets werwas sonicavolume ofmetric flasThe syrupadjusted towere thenexperiment

2.6. The st

To investhis work wmolecules.fering subsand d-gluc

Fig. 1. The stnol and d-glu

3. Results and discussion

3.1. Electropolymerization of molecularly imprintedpolypyrrole

The electrochemical behavior of pyrrole was investigatedin aqueous solution of 0.1 M LiClO4 using potential cyclingbetween 0.6 and +1.40 V (versus Ag/AgCl). Electrooxidationof the pyrrole monomer occurs at the anode, and the resultingpolymer deposits onto the surface of pencil graphite electrode.An anodic peak of pyrrole was observed at a peak potential of1.10 V. The corresponding reduction process was not observedon the cyclic voltammogram. The oxidation peak correspondsto the formation of pyrrole radical cations. Fig. 2a demonstratesfour cycles obtained in the same solution. The formation andgrowth of the polymer film can be easily seen in this figure. Thepeaks due to the oxidation and reduction of the film increase inintensity as the film grows. A broad oxidation peak was observedat the peak potential of +0.10 V and reverse cathodic peak wasseen at a peak potential of 0.20 V.

For imprinted electropolymerizations, paracetamol wasto the electrochemical cell at a concentration of 20 mM.

demonstrated cyclic scans of electropolymerization ofe in the presence of paracetamol. The effect of parac-l (template) on the electropolymerization of pyrrole cann easily in this figure. The oxidation peak potential ofrrole shifted to more anodic potentials, from 0.1 to 0.30 V,

yclic). (a) MmM)te: 0.l were examined for estimation of paracetamol. Thee finely powdered and dissolved in water. The solutionted for 10 min and filtered. An aliquot of appropriatestock solution was transferred into 250 mL volu-

k and volume was completed with buffer (pH: 7.0).was transferred to a 100 mL flask and volume wasthe same pH value with buffer solution. The samplesspiked with appropriate amount of paracetamol fors.

ructure of interferents

tigate the selectivity of the MIP and NIP electrode inas evaluated in the presence of different interfering

The structure of paracetamol and some possible inter-tances, dopamine, phenacetin, ascorbic acid, phenolose were given in the Fig. 1.

ructure of paracetamol, dopamine, phenacetin, ascorbic acid, phe-cose.

addedFig. 2bpyrroletamobe seepolypy

Fig. 2. C(0.05 Mmol (20electrolyvoltammograms taken during the electropolymerization of pyrroleultisweep cyclic voltammograms without and (b) with paraceta-

onto a pencil graphite electrode (scan rate: 100 mV s1; supporting1 M LiClO4; number of scans: 4).

L. Ozcan, Y. Sahin / Sensors and Actuators B 127 (2007) 362369 365

Fig. 3. Schemetamol fromelectrode.

in the presthat the temBecause oftransfer wamol molecthe electropmatrix. Thdiffusion onumber of rnon-electromolecularthe first scmeric layethis layersites.

Duringparacetamomatrix as awith the pying and repolypyrroleFig. 3. Themolecule foNH group

ffectpara

betwuctuher

H gf theinkinichescess

tamoFig. 4. E0.25 mM

occur

mol strunits. Tthe Natom ocross lwith ning proparaceatic representation of (a) imprinting and (b) removal of parac-paracetamol imprinted polypyrrole modified pencil graphite

ence of paracetamol. This oxidation peak indicatesplate is becoming part of the polymeric chain [13].the polymerization solution was not stirred, the masss occurred by diffusion controlled process. Paraceta-ules diffuses towards the surface of the PGE duringolymerization process and trapped into the polymer

e creation of the molecular imprints favored by thef the electroactive template, generating a far higherecognition sites than those previously obtained with aactive template. If the template is non-electroactive,diffusion towards the electrode is interrupted afterans by the formation of the non-conductive poly-r, which prevents the template forming part ofand thereby reducing the number of recognition

the electrodeposition of the conductive polymer,l template molecules are trapped in the polymerresult of the ability of these molecules to interact

rrole units. The schematic representation of imprint-moval of paracetamol from paracetamol imprinted

modified pencil graphite electrode was shown inoxygen atom in the C O group of the paracetamolrms a hydrogen bond with the hydrogen atom in theof the pyrrole units (Fig. 3). Hydrogen bonding could

ing of the ftemplate, vextraction,the use of sing the sweremove themer was co

solution usiwork.

3.2. Effect

The pHbility of thbe the lowIt can be cat neutral prespondingof the medmodified peto 7.0.

The meetamol is deffect of thmol (0.25 mThe paracethe pH incrof 7.0, withdation peakat higher ioof pH on the MIP modified pencil graphite electrode response forcetamol in a phosphate buffer solution with KCl.

een the hydrogen in the hydroxyl group of paraceta-re and the nitrogen atom of the NH group of pyrrolee may be a hydrogen bond between nitrogen atom inroup of the paracetamol molecule and the hydrogen

NH group of pyrrole units. Chain branching andg in PPy [14] generate a three-dimensional matrixcontaining the template paracetamol. This imprint-creates a microenvironment for the recognition of

l molecule based on shape selection and position-unctional groups. In order to remove the entrappedarious methods are possible: microwave assistedoxidation-reduction of the template in the polymer orolvent that strongly interacts with the polymer caus-lling of the coating necessary for template release. Totemplate inside the polypyrrole, the imprinted poly-nditioned in 0.1 M KCl + 0.05 M phosphate bufferng potential cycling between0.6 and +1.00 V in our

of pH

of the solution has a significant influence on the sta-e polymeric film. The signal of the polymer shouldest to avoid an interaction with paracetamol signal.

oncluded that the polymer response was the lowestH, while at more acidic and basic pH there is a cor-signal to the polymer structure. Therefore the pH

ium in which the measurement with the polypyrrolencil graphite electrode is to be made should be equal

chanism for the electrochemical oxidation of parac-ifferent depending on the pH of the medium. The pHe MIP electrode is illustrated in Fig. 4 for paraceta-M) at different pH, in the range of 311, by DPV.

tamol signal shifted to more cathodic potentials aseases (Fig. 4). The best results are obtained at a pHa 0.05 M phosphate and 0.1 M KCl, giving an oxi-at 450 mV. No further improvements were observednic strength.

366 L. Ozcan, Y. Sahin / Sensors and Actuators B 127 (2007) 362369

Fig. 5. Differparacetamol aparacetamol ain a phosphat

3.3. Electr

The elegated by Melectrode isat pH 7.0trode by Dat about 37MIP electrAg/AgCl athe paracetenhanced ppotential ofare a cleartowards the

The caliand NIP eDPV peakparacetamoregions. Thtration rangof 0.996. Tthan the fir1.254.5 mis 7.9 10lated detecPPy surfacof MIP elemaking it plow as 0.5at NIP eletion rangewas muchparacetamoand 5 mM.

3.4. Effect

The modetermined

ffectnon-

mM pmol i

tionooder c

cetatrati

n theV aof solec

ts. Tckneate)de trrolese ine conIP el

IP bem m

50 m

ffect of the electropolymerization cyclesential pulse voltammograms for (a) 0.25 mM and (b) 1.0 mMt non-imprinted polypyrrole (NIP) (c) 0.25 mM and (d) 1.0 mMt molecularly imprinted (MIP) modified pencil graphite electrodee buffer medium at pH 7.0 with 0.1 M KCl.

ochemical behavior of paracetamol

ctrochemical behavior of paracetamol was investi-IP and NIP electrode. The catalytic effect of the MIPdemonstrated in Fig. 5 for paracetamol (0.25 mM)recorded at a NIP electrode and the MIP elec-PV. Paracetamol gives an oxidation peak response0 mV versus at the NIP electrode, while the use of

ode leads to an anodic peak at about 450 mV versusnd the peak current increased greatly. In neutral mediaamol oxidizes to N-acetyl-p-quinoneimine [13]. Theeak current response and a shift in the oxidationparacetamol by about 80 mV in the anodic direction

evidence of the catalytic effect of the MIP electrodeoxidation of paracetamol.

bration curves were observed for paracetamol at MIPlectrode at pH 7.0. The calibration curve for thecurrent observed for paracetamol oxidation versusl concentration at MIP electrode shows two lineare first region demonstrates linearity over a concen-e of 5M to 0.50 mM with a correlation coefficienthe slope of the second linear region was smaller

st regions slope with a wide concentration range ofM (0.990). The detection limit (3) of paracetamol7 M (S/N = 3). The percentage error in the calcu-

Fig. 6. Eand ()for 0.25paraceta

merizawith gmonom

to paraconcen

tions i0.60resultsplate mimprinthe thi(templelectroing pydecreapyrroland Nble (iMshouldoptimuabout

3.5. E

tion limit was estimated to be 1.0%. Modification ofe by imprinting remarkably improves the reactivityctrode towards the oxidation of paracetamol, thus,ossible to detect paracetamol in a solution up to asM. The calibration curve observed for paracetamol

ctrode was also show a linearity over a concentra-of 50M to 0.50 mM. However, the current rangesmaller than that of observed at MIP electrode. Thel oxidation current remained constant between 2.0

of the monomer concentration

nomer concentration during polymerization alsothe analytical behavior of the sensor. Electropoly-

The opting layerexperimentnumbers ofPy and 20 mand +0.80 Velectropolylinearity ofnumber ofHigher cycand therefoaccessibleelectrodesthe numberof the monomer concentration on () molecularly imprinted (MIP)imprinted polypyrrole (NIP) modified pencil graphite electrodearacetamol. Response was measured thorough DPV in 0.25 mM

n a phosphate buffer medium at pH 7.0 with 0.1 M KCl.

using low monomer concentrations produced sensorsanalytical behavior. To determine the effect of

oncentration on the response of both MIP and NIPmol, the films were grown in solutions of constanton of paracetamol and varying pyrrole concentra-range of 25500 mM by cycling potential between

nd +0.80 V for the same cycles. Fig. 6 shows theuch a comparison. The binding ability of the tem-ules onto the coating film depends on the number ofhe monomer concentration should be proportional toss of the deposit and amount of imprinted moleculein the polymeric matrix. The response of the MIPo paracetamol was found to increase with increas-concentration up to 50 mM. There was considerablethe response of MIP electrode below and above thiscentration. The current difference between the MIPectrode for paracetamol should be as high as possi-iNIP). In addition, the signal of the NIP electrode

nearby zero (iNIP 0). It can be concluded that theonomer concentration under these conditions was

M.imum number of CV cycles to use to form the sens-of the electrode was determined from a series ofs in which electrodes were fabricated with differentcycles in aqueous solution of 0.1 M LiClO4, 0.05 MM paracetamol by cycling potential between 0.60. The number of cycles applied to the cell during themerization was found to affect the sensitivity andthe sensor. The MIP electrode produced at lower

cycles exhibited favorable analytical performance.les lead to more extensive electropolymerization,re to the formation of thicker sensing film with lessimprinted sites. The response of the MIP and NIPto paracetamol was found to increase with increasing

of cycles up to 4 and 6, respectively (Fig. 7). There

L. Ozcan, Y. Sahin / Sensors and Actuators B 127 (2007) 362369 367

Fig. 7. Effectnon-imprinteda phosphate b

was considtrode belowdifferencewas obtaintion. Thereto be 4. Thpassed thro500 nm.

3.6. Effect

Dopamiprime rolecular and hquite similafluids andlarity to thstructures oFig. 1. Thefor dopami0.27 V diffand paraceany interacof the tempwas shownto investigtion on thesensor behemployed icentration gparacetamogreat numbusing highcause decretation, a greof paraceta

The respto increaseand 20 mMof MIP elec

espocetame resp

cess

se toine.pamhere0 mM

ffect

selealuametted pposse, pht in bpara

volta(0.2

nterfe of

lectroes, there was no substantial change in current responseof the number of cycle to () molecularly imprinted (MIP) and ()polypyrrole (NIP) modified pencil graphite electrode response in

uffer medium at pH 7.0 with 0.1 M KCl.

erable decrease in the performance of the MIP elec-and above this number of cycles. The highest current

between the MIP and NIP electrode for paracetamoled by applying 4 cycles in the electropolymeriza-fore the optimum polymerization cycles was founde thickness of the PPy was measured by the chargeugh the electropolymerization process [15] was about

of the template concentration

ne is a most significant neurotransmitter, plays ain the functioning of the central nervous, cardiovas-ormonal systems and the structure of dopamine isr to paracetamol. Dopamine is present in biological

may interfere with paracetamol because of its simi-at of paracetamol and electrochemically active. Thef dopamine and the other interferents are given inoxidation peak potentials are +0.18 and +0.45 V

ne and paracetamol, respectively at MIP electrode.erence in the oxidation peak potentials of dopaminetamol was allowed to analyse paracetamol withouttion with dopamine in biological samples. The effectlate concentration during the film electrodepositionin Fig. 8. Dopamine was used as a control substance

Fig. 8. R() paraelectrod

It is nerespondopamand dotion. Tto be 2

3.7. E

Thewas ev

Voltamimprinsome

glucospresention ofpulseetamoleach iabsencMIP eall casate the effect of template (paracetamol) concentra-response of the MIP electrode in this figure.The

avior was influenced by the template concentrationn the electrodeposition process. As the template con-rows in the polymerization solution, the response tol of the MIP electrode obtained is also higher. Theer of specific cavities for paracetamol was generatedconcentration of template. However, this process mayase the selectivity of the sensor. Because of this limi-ater number of cavities will permit a greater diffusionmol to the active surface of the MIP electrode.onse of the MIP electrode to paracetamol was foundwith increasing paracetamol concentration up to 5(Fig. 8). There was a small decrease in the responsetrode above this paracetamol concentration (20 mM).

for 0.25 mMexcess of itions of therelative toof phenacelogical samelectrode isat least fourphenol proeven whenis, the elecmodified pmol molecfunctionalNIP electronse of MIP electrode was measured through DPV in solutions withol as a template and () dopamine as a control substance to MIPonse in a phosphate buffer medium at pH 7.0 with 0.1 M KCl.

ary to select a template concentration to which theparacetamol is highest, without obtaining a signal forThe highest current difference between paracetamoline was obtained with 20 mM paracetamol concentra-fore the optimum template concentration was found

.

of interferents

ctivity of the MIP and NIP electrode in this workted in presence of different interfering molecules.ric responses of paracetamol imprinted and non-olypyrrole film were examined in the presence of

ible interfering substances like ascorbic acid, d-enacetin, dopamine and phenol. These substances areiological fluids and may interfere with the determina-cetamol through conventional methods. Differentialmmograms were taken for the oxidation of parac-5 mM) after addition of varying concentration of

erent (0.252.5 mM). The obtained currents in theany interferent were 42 and 115A with NIP andde, respectively. The results are given in Table 1. Inparacetamol in the presence of less than two foldnterferents for MIP electrode. At higher concentra-se interferents the variation was within 7.170Athat in their absence. However, the concentrationstin and dopamine are not as high as 1.0 mM in bio-ples. Thus, the response of paracetamol at the MIPnot affected by the interferents examined here belowfold concentrations. It was found that D-glucose and

duce negligible changes in the paracetamol responsean analyte-inteferent ratio of 1:10 was used. Thattropolymerized-molecularly imprinted polypyrroleencil graphite electrode can recognize the paraceta-ules by means of shape selection and the size ofgroups. However, the response of paracetamol at thede is affected by the interferents.

368 L. Ozcan, Y. Sahin / Sensors and Actuators B 127 (2007) 362369

Table 1Effect of interferents on the differential pulse voltammetric response of 0.25 mM paracetamol at the MIP and NIP electrode

Interferent Concentration of interferents (mM) Change in current responseawith M

b

Phenol

Glucose

Phenacetin

Dopamine

Ascorbic acid

a The curreb The curre

Table 2A comparison ons (tmodified penc

Tablet/syrup n

MinosetMinoset PlusVermidonTylolHotCalpol syrup

a g/tablet.b g/20 g.c mg/5 mL.

3.8. Analy

Variousined for estmethod. Soand syrupcentrationpulse voltacal conditiopulse voltadilution facconcentratiment with(as shownmol amounsyrup arechemical dboth detectconditions.and DPV,observe thapurposes.0.25 mM paracetamol

0.25 0.6781.00 1.1502.50 2.1000.25 0.8521.00 1.4952.50 2.645

0.25 2.1630.50 3.2451.00 7.1700.25 1.3700.50 2.9801.00 5.2500.25 0.620.50 1.781.00 2.350

nt in the absence of any interferent was 115A (with MIP).nt in the absence of any interferent was 42A (with NIP).

of observed and reported paracetamol concentration in pharmaceutical preparati

il graphite electrode and HPLC

ame Reported content Detected content (with MIP) R.S.D. (%) (n0.500a 0.487a 1.260.250a 0.236a 0.670.500a 0.496a 0.810.500b 0.492b 1.62120c 117c 1.55

sis of commercial samples

tablets and syrup having paracetamol were exam-imation of paracetamol by MIP electrode and HPLClution obtained by dissolution of paracetamol tabletswere subsequently diluted so that paracetamol con-lies in the range of calibration plot. Differentialmmograms were then recorded under exactly identi-ns that were employed while recording differentialmmograms for plotting calibration plot. Keepingtor in consideration, it was found that paracetamolon determined using this method is in good agree-the manufacturers stated contents of paracetamolin Table 2). Experimentally determined paraceta-t and reported paracetamol amount in tablets and

listed in Table 2. In order to validate the electro-etection we have compared the obtained results withion methods, by using the optimal chromatographicTable 2 shows the obtained data when the HPLC

using MIP electrode, are used. In this table we cant both detection methods were useful for analytical

3.9. Repro

The reppencil grapmol. The pwith six eleThe responof 1.3% co

The MItimes withnatively anprocedure

4. Conclu

Electrocappealing ctrochemistrand is likelsmall saming high sstudy, paraforIP (A)

Change in current response for 0.25 mMparacetamol with NIP (A)3.3607.351

10.9900.8233.8845.209

8.86312.51819.0216.813

12.93015.280

4.6917.195

10.033

ablets and syrups) using DPV at molecularly imprinted polypyrrole= 3) Detected content (with HPLC) R.S.D. (%) (n = 3)0.496a 0.420.245a 0.490.495a 0.550.494b 0.48118c 0.31

ducibility of the MIP electrode

roducibility of the molecularly imprinted modifiedhite electrode was investigated for 0.25 mM paraceta-eak current response of paracetamol was determinedctrodes which produced under the same conditions.se peak intensity showed a relative standard deviationnfirming that the results are reproducible.P PG electrodes could be used at least 10 or 15subsequent washing and measuring operations. Alter-other MIP-PGE could be easily prepared with the

described above.

sion

hemistry has many advantages making it anhoice for pharmaceutical analysis. The role of elec-y in pharmaceutical analysis has been well defined,y to get preference when low analyte concentrations,ple volumes, or complex sample matrices requir-pecificity challenge the analytical method. In thiscetamol imprinted electrodes formed by the cyclic

L. Ozcan, Y. Sahin / Sensors and Actuators B 127 (2007) 362369 369

voltammetric deposition of polypyrrole film on pencil graphiteelectrode in the presence of target paracetamol have been suc-cessfully fabricated. Molecular imprinting was shown to be aneffective way of growing the polymer coating directly onto a dis-posable electrode. A linear relationship between paracetamolconcentration and current response was obtained with excel-lent reproducibility of the current and a low detection limit of7.9 107 M. Molecularly imprinted polypyrrole modified pen-cil graphite electrode showed a stable and reproducible responsewithout any influence of interferents commonly existing in phar-maceutical samples. The proposed low cost chemical sensorcould find application in the measurement of paracetamol levelin clinical samples as well as in pharmaceutical industry.

Acknowledgements

Financial support of Anadolu University Research Found(Project Nos.: 031064 and 051060) is gratefully acknowledged.

References

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Biogra

Leventhis bach1999. InAnadoluAnadolubiosenso

Yucel SPhD degand 2002004 inworkedinterestssensors

chemistn was born in Sakarya, Turkey on October 16, 1977. He receivedegree in chemistry from Anadolu University, Eskisehir, Turkey inhe has received his master degree in Department of Chemistry atersity. He has been a PhD student in Department of Chemistry atersity since 2002. He research interests include electrochemicalodified electrodes and conducting polymers.

was born in Ankara, Turkey in 1969. He received his master andin the Department of Chemistry at Hacettepe University in 1996pectively. He has worked as an assistant professor from 2000 toepartment of Chemistry at Anadolu University. Since 2004, he

associated professor in the same department. His current researchlectroanalytical chemistry, conducting polymers, electrochemicalosensors, modified electrodes, electrocatalysis, and electroorganic

Determination of paracetamol based on electropolymerized-molecularly imprinted polypyrrole modified pencil graphite electrodeIntroductionExperimentalChemicals and reagentsApparatusPreparation of MIP and NIP electrodesElectroanalytical measurementsSample preparationThe structure of interferents

Results and discussionElectropolymerization of molecularly imprinted polypyrroleEffect of pHElectrochemical behavior of paracetamolEffect of the monomer concentrationEffect of the electropolymerization cyclesEffect of the template concentrationEffect of interferentsAnalysis of commercial samplesReproducibility of the MIP electrode

ConclusionAcknowledgementsReferences