Applied Che매S며，

Vol. 12, No. I , May 2008, 85-88

M피ified Electrode-를 이용한 Phannaceu디cal Fonmlations 에서의

R표lSera깅de의 전압전류법적 정량

Saikh Mohammad Wabaidur. Seikh Mafiz Alam. Mir Azam Khan. 이상학 f

경북대학교 화학과

Voltammetric Determination of Bensera깅de in pharπlace따ical

Fornn..dations Using Polymer M피ified Elecσode

Saikh Mohammad Wabaidur. Seikh Mafiz Alam , Mir Azam Khan ‘ Sang Hak Lee t

Department of Chemistry. Kyungpook National University. Taegu. 702-70 1. Korea

ABSTRACT

Poly (4 - (2-pyridylazo) -resorcinol) (PAR) film modified glassy carbon

electrode (GCE) was used for the determination of benserazide (BZ) as it

does not shows any peak at bare glassy carbon electrode. BZ was accumulated

at the PAR modified GCE surface under open circuit condition and givesensitive oxidation peak at 230 mY. Experimental conditions such as supporting

electrolyte. pH value and accumulation time were optimized for the investigated

method. BZ gives linear response over the range of 0.01 mM to 0.20 mM. The

lower detection limits were found to be 0.002mM. The investigated

electrochemical method was successfully applied for the determination of BZ in

pharmaceutical formulation

Keywords: Electrochemical system. PAR. benserazide. madopar tablet

1. INTRODUCTION

Benserazide [2-amino-3-hydroxy-N- {(2 ,3 ,4-trihydroxypheny l) methy l}

propane hydrazide] (BZ) is an irreversible inhibitor of peripheral L-aromatic amino

acid decarboxylase (AADC). BZ at the recommended therapeutic dose not cross

the blood-brain barrier to any significant degree and combined therapy with

levodopa (LD) reduces the amount of levodopa required for optimal therapeutic

benefit and permits an earlier response to therapy [1]. Scientific literature

reports few analytical procedures such as spectrophotometry [2-5] , capillary

electrophoresis [6-9] and high performance liquid chromatography [1 0] for the

determination of BZ in pharmaceutical preparations. But hitherto , there are no

reports concerned on the determination of BZ by cyclic voltammetric (CV)

method , particularly using PAR film modified GCE. In the current study , PAR

polymer film modified GCE is described for the determination of BZ. The

proposed method possesses many advantages such as low detection limit, fast

response , simple and inexpensive instrumentation. The practical application was

demonstrated to determine BZ in tablets with good result.

85

86 Saikh Mohammad Wabaidur' Seikh Mafiz A1am . Mir Azam 때Jan' 이상학

2. EXPERIMENTAL

Apparatus

Potentiostat (RS-PDAl , Palm Instruments , Netherland) , bare or PAR modified

GCE (3.0mm in diameter) as working , platinum electrode as auxiliary and Ag/AgCI

electrode was used as a reference. Ultra sonic bath (Bransonic 5210, USA) and a

pH meter (Mettler Toledo MP220 , UK) were used for sonication and pH

measurements.

Reagents

Poly (4- (2-pyridylazo) -resorcino l) (PAR) was purchased from Aldrich (USA),

Standard solution of 0.5 mM benserazide hydrochloride (Sigma , USA) are

prepared in 0.1 M phosphate buffer solution (PBS) of pH 5 and was protected

from light and stored in 4-5 °c. NaH2P04.H20 , Na2HP0 4.2H20 (Merck , Germany)

used for PBS. All solutions were prepared with double-distilled wate r.

Pharmaceutical sample solution preparation:

The average weight of 10 Madopar tablets (Roche South Korea) containing 25 mg

of BZ was finely powdered by pestle in a mortar. Amount of the sample required

for 0.5 mM of BZ was transferred to 25 mL volumetric flask and was dissolved in

PBS of pH 5 , sonicated for 5 min. and was filtered and stored at refrigerator.

Preparation of poly PAR mo마lied GeE

The GCE surface was initially polished with fine emery paper followed by 0.3 11m

and 0.05 11m alumina powder and finally sonicated with Milli-Q water for 3-5

minutes. The GCE was modified as reported previously [11 , 12]. Before electro

polymerization the polished electrode was electrochemically pretreated in 0.1 M

PBS pH 5 by scanning 20 times between electrode potential of -0.5 V and 1.8V

at scan rate of 100 mVIs. The PAR film was deposited on the pretreated surface

by scanning 20 times of the corresponding monomer in 1 mM PAR under the

same conditions as those in the pretreated procedure. The film deposited

electrode was washed with distilled water.

General procedure

The PA R- coated GeE w’ as first activated in pH 5 phosphate buffers by cyclic

voltammetric sweeps between 0.0 and 0.8 V until stable cyclic voltammograms

were obtained. Then PAR-coated GCE was transferred into new cell containing

pI I 5 phosphate buffer and certain concentration of anaJyte. After 2 minutes of

open-circuit accumulation , the cyclic voltammogram from 0.0 to 0.8 V at a scan

rate 100 mV/s was recorded for the analyte and the peak appeared at 230 mY.

After ever~! measuremen t, the PAR-modified GCE was dipped into 0.1 M NaOH

solution for few seconds and scan 5 times in pure phosphate buffer (pH 5).

3. RESULTS AND DISCUSSION

Electrochemistry of BZ on PAR modified GCE.

웅용화학， 제 12 권 제 l 호， 2008

87Voltammetric Determination of Benser때de in Pharmaceutical Formulations Using Polymer M여ified Elecσ'Ode

In the potential range 0.0 to 0.8 V, no observable peaks appeared for PBS. But, a

well- shaped and highly sensitive oxidation peak appears at 21 a mV after adding

BZ (Fig. I). The absence of reduction peak , suggesting that the electrode reaction

of 8Z at the PAR modified electrode is totally irreversible. The oxidation peak

second cyclic vo1tammetric sweep decreases as compared to the

first peak , indicating the adsorption of BZ on PAR film. The electrode surface was

cleaned by above mentioned procedure for reproducible results.

Parameter optimization for BZ at PAR modifi능d electrode:

The optimization of supporting electrolyte , pH value , accumulation time , and scan

rate have been carried out to get the maximum response. Accumulation time has

oxidation peak current of BZ

required for maximum accumulation of BZ was 2

optimum. The optimum scan rate was 100 mVIs. The electrochemical behavior of

BZ in phosphate buffer , sodium citrate-HCl buffer. Britton-Robinson buffer were

studied. All the experiment was performed in 27 °c. The best oxidation response

was obtained in pH 5 phosphate buffer and was choosen as optimal.

current in the

time

aschosen

optimum

was

the

and

and

minutes

theeffect onobviousan

Calibration curve

The linear increase in the current response for concentration of BZ using CV are

shown in Fig. I. Using optimum conditions linear calibration curve was obtained

for BZ over the range of 0.01 mM to 0.20 mM. The equation for calibration curve

was y = 0.398 + 0.1682x (R=0.9976) , where x is the concentration of BZ (mM)

be

80th

tofound

mM.0.007

were

was

lower detection limits

0.002 mM. Similarly the calculated limit of quantification

values confirmed the sensitivity of the proposed methods.

The(μA).current intensityISyand

10

(〈그----E그Q

0.80.80.7。.0.3 O.‘ 0.5

PotentlallV)0.2。，0.0

-2

Fig. 1. CV of BZ of different cone. at the PAR -modified electrode at

pH 5. Curves a-e: blank , 7x10-n, 12xIO-6, 2.0x10- 5, 2.7xIO- 5 mol

L -I , respectively. Accumulation time 120 s; scan rate 0.1 Vs- 1.

Applied Chemistry, VoL 12, No.1, 2003

88 S갱kh Mohammad Wabaidur' S잉kh Mafiz Alam . Mir Azam 때lan • 이상학

Determination of BZ in pharmaceutical preparation.

CV method was applied to the direct determination of BZ in madopar tablets using

calibration curve. The results for the analysis of madopar tablets are shown in

table- I. The results show that the proposed electrochemical method can be

successfully applied for the determination of BZ in pharmaceutical preparation.

S빼pie BZ Claimed/tablet BZ found

Madopar tablet 25.0 mg 25.20 土 0.81 mg

Table 1. Application of the voltammetric method to the determination of BZ in

tablets and recoveries from spiked tablets.

4. CONCLUSIONAn electrochemical method was developed and successfully applied for the

determination of benserazide (BZ) using PAR modified GCE. In the anodic sweep

from 0.0 to 0.8 V, BZ was adsorbed at the modified electrode surface and

oxidized at 230 mV. The experimental conditions like supporting electrolyte ,

accumulation time and scan rate were optimized for the determination. The

proposed method is simple , sensitive , easy to apply and economical for routine

analysis. The developed method was applied for the determination of BZ using CV

method in pharmaceutical formulations with reliable results.

5. ACKNOWLEDGEMENTSKyungpook National University is thankfully acknowledged For financial support.

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옹용화학， 제 12 권 제 l 호， 2008