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