Electrochemical Behavior of Chalcone at a Glassy Carbon Electrode and Its Analytical Applications

doi:10.4236/ajac.2012.39086

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American Journal of Analytical Chemistry, 2012, 3, 656-663

http://dx.doi.org/10.4236/ajac.2012.39086 Published Online September 2012 (http://www.SciRP.org/journal/ajac)

Electrochemical Behavior of Chalcone at a Glassy Carbon

Electrode and Its Analytical Applications

Keerti M. Naik, Sharanappa T. Nandibewoor*

P. G. Department of Studies in Chemistry, Karnatak University, Dharwad, India

Email: *[email protected]

Received May 5, 2012; revised June 8, 2012; accepted June 18, 2012

ABSTRACT

A simple and rapid method was developed using cyclic, differential pulse and square wave voltammetric techniques for

the determination of trace-level chalcone at a glassy carbon electrode. Chalcone could produce two anodic peaks at

about 0.514 V and 1.478 V and a cathodic peak at about −0.689 V. The differential pulse voltammerty presents a good

linear response as compared to square wave voltammetry in the range of 0.2 - 10 μM with a detection limit of 0.18 μM.

The proposed method was used successfully for its quantitative determination in spiked human plasma and urine as real

samples.

Keywords: Chalcone; Voltammetry; Glassy Carbon Electrode; Electrochemical Determination; Oxidation

1. Introduction

Chalcone (1,3-Diphenyl-2-propen-1-one) (Scheme 1) is an

aromatic ketone that forms the central core for a variety

of important biological compounds, which are known col-

lectively as chalconoids. They show antibacterial, antifungal,

antitumor and anti-inflammatory properties [1]. Some cha-

lcones demonstrated the ability to block voltage-dependent

potassium channels [2]. They are also intermediates in the

biosynthesis of flavonoids, which are substances wide-

spread in plants and with an array of biological activities.

Chalcones are also intermediates in the Auwers synthesis

of flavones. Due to ineffective drugs, cancer is the second

most leading cause of death after heart attack. Therefore,

the researchers have accelerated their efforts for the gen-

eration of new anticancer drugs with high therapeutic in-

dex. In this connection, a clinically effective antitumor

derivative of chalcone (calicheamicin) has stimulated the

investigators to concentrate their studies on chalcones and

related compounds [3].

O H

Scheme 1. Chemical structure of chalcone.

Electrochemical methods have proved to be very sen-

sitive for the determination of organic molecules, includ-

ing drugs and related molecules in pharmaceutical dosage

forms and biological fluids [4-8]. The advance in experi-

mental electrochemical techniques in the field of analysis

of drugs is due to their simplicity, low cost and relatively

short analysis time when compared with the other tech-

niques. The use of carbon based electrodes, especially

glassy carbon electrode, for electroanalytical measure-

ments has increased in recent years because of their ap-

plicability to the determination of substances that un-

dergo oxidation reactions, a matter of great importance in

the field of clinical and pharmaceutical analysis. Redox

properties of drugs can give insights into its metabolic

fate or their in vivo redox processes or pharmaceutical

activity [9,10].

A review of the literature reveals that only the oxida-

tion of chalcone by trichloroisocyanuric acid in HOAc-

HClO4 medium [11] and the interaction of substituted

chalcone with DNA [12] have been reported. However,

no methods for determination of chalcone have been re-

ported so far. There is also no report on the electro-oxi-

dation of chalcone with any of the electrodes. In view of

the pharmaceutical importance of chalcone and the lack

of literature on its voltammetric determination, the elec-

tro oxidation of chalcone necessitates a method to be de-

veloped. The aim of the present study is to establish the

suitable experimental conditions, to investigate the oxid-

ation mechanism of chalcone and determine chalcone in

spiked human plasma and urine samples using cyclic, squ-

are wave and differential pulse voltammetric techniques.

*Corresponding author.

K. M. NAIK, S. T. NANDIBEWOOR 657

2. Experimental

2.1. Materials and Reagents

Pure chalcone in powdered form was obtained from Sigma

Aldrich and used without further purification. A stock solu-

tion of chalcone was prepared by direct dis-

solution in methanol, since it is insoluble in water. The

phosphate buffers from pH 3 - 11.2 were prepared in double

distilled water as described by Christian and Purdy [13].

All other reagents used were of analytical or reagent grade

and their solutions were prepared with double distilled

water.

()

110 M

−

2.2. Instrumentation

Electrochemical measurements were carried out on a CHI

630 D electrochemical analyzer (CH Instruments Inc.,

USA). The voltammetric measurements were carried out

in a 10 ml single compartment three-electrode glass cell

with Ag/AgCl as a reference electrode, a platinum wire

as counter electrode and a 3 mm diameter glassy carbon

electrode (GCE) as the working electrode. All the poten-

tials are given against the Ag/AgCl (3 M KCl). The pH

measurements were performed with Elico LI120 pH me-

ter (Elico Ltd., India). All experiments were carried out

at an ambient temperature of 25˚C ± 0.1˚C.

The area of the electrode was calculated using 1.0 mM

K3Fe(CN)6 as a probe at different scan rates. For a reversi-

ble process, the Randles-Sevcik formula has been used [14].

()

i2.6910=× 2 1212

0 0

nADCυ (1)

where ipa refers to the anodic peak current, n is the num-

ber of electrons transferred, A is the surface area of the

electrode, D0 is diffusion coefficient, υ is the scan rate

and C0 is the concentration of K3Fe(CN)6. For 1.0 mM

K3Fe(CN)6 in 0.1 M KCl electrolyte, n = 1. D0 = 7.6 ×

10−6 cm2·s−1 [14], then from the slope of the plot of ipa ver-

sus υ1/2, relation, the surface area of electrode was calcu-

lated. In our experiment, the slope obtained was 2.46 ×

10−6 and the surface area of glassy carbon electrode was

calculated to be 0.033 cm2.

2.3. Analytical Procedure

The GCE was carefully polished using 0.3 micron Al2O3

slurry on a polishing cloth before each experiment. After

polishing, the electrode was rinsed thoroughly with water.

After this mechanical treatment, the GCE was placed in

buffer solution and various voltammogramms were re-

corded until a steady state baseline voltammogram was

obtained.

The GCE was first activated in phosphate buffer (pH

3.0) by cyclic voltammetric sweeps between −2 to and

3.0 V until stable cyclic voltammograms were obtained.

Then electrodes were transferred into another 10 ml of

phosphate buffer (pH 3.0) containing proper amount of

chalcone. After accumulating for 10 s at open circuit under

stirring and following quiet for 10 s, potential scan was

initiated and cyclic voltammograms were recorded between

−2 and 3.0 V, with a scan rate of 50 m·Vs−1.

2.4. Plasma sample Preparation

Human blood samples were collected in dry and evacu-

ated tubes (which contained saline and sodium citrate so-

lution) from same healthy volunteer. The samples were

handled at room temperature and were centrifuged for 10

min at 1500 rpm for the separation of plasma within 1

hour of collection. The samples were then transferred to

polypropylene tubes and stored at 20˚C until analysis.

The plasma samples, 0.2 mL, were deproteinized with 2

mL of methanol, vortexed for 15 minutes centrifuged at

6000 RPM for 15 min, and supernatants were collected.

The supernatants were spiked with an appropriate volume

of chalcone. Appropriate volumes of this solution were

added to phosphate buffer pH 3.0 as supporting electro-

lyte and the voltammograms were then recorded.

3. Results and Discussion

3.1. Cyclic Voltammetric Behavior of Chalcone

In order to understand the electrochemical process occur-

ring at the glassy carbon electrode, cyclic voltammetry

was carried out. Chalcone was oxidized on glassy carbon

electrode between pH 3.0 and 11.2 of phosphate buffer,

producing two well-defined oxidation peaks and one re-

duction peak. The cyclic voltammograms of chalcone at

pH 3.0 in phosphate buffer was as shown in Figure 1.

The blank solution without chalcone was shown by curve

(b) and anodic peaks corresponding to chalcone oxida-

tion appeared at 0.514 V (peak A) and 1.478 V (peak B)

and a cathodic peak at −0.689 V (peak C) as shown in

Figure 1. Cyclic voltammogram obtained for 10 μM chal-

cone on glassy carbon electrode in pH 3.0 0.2 M buffer: (a)

chalcone and (b) blank run without chalcone at ν = 50 m·Vs−1:

accumulation time: 10 s (at open circuit).

K. M. NAIK, S. T. NANDIBEWOOR

658

curve (a). The peak current for the first wave was found

to increase with increase in concentration of chalcone.

The plot ip vs. concentration was linear in the range 0.2 to

10.0 μM and deviates from linearity above 10 μM. This is

due to the adsorption of chalcone or chalcone oxidation

product at higher concentration.

It is shown that the reduction peak was observed in the

reverse scan, suggesting that the electrochemical reaction

was a quasi-reversible process [15]. Nevertheless, it was

found that the oxidation peak current of chalcone showed

a remarkable decrease during the successive cyclic volta-

mmetric sweeps. After every sweep, the peak current dec-

reased greatly and finally remained unchanged. This phe-

nomenon may be attributed to the consumption of adsor-

bed chalcone on the electrode surface or due to the fact

that the adsorption of oxidative product occurs at the elec-

trode surface. Therefore, the voltammograms correspond-

ing to the first cycle and peak A were generally recorded,

since peak A was more intense than B.

3.2. Influence of Accumulation Potential and

Time

It was important to fix the accumulation potential and time

when adsorption studies were undertaken. Both conditions

could affect the amount of adsorption of chalcone at the

electrode. Bearing this in mind, the effect of accumula-

tion potential and time on peak current response was stud-

ied by CV. The concentration of chalcone used was 10 μM.

When accumulation potential was varied from +0.4 to

−0.4 V, the peak current changed a little. Hence, accu-

mulation at open circuit was adopted. The peak current

increased very rapidly with increasing accumulation time,

which induced rapid adsorption of oxidative product on

the surface of the GCE. The peak current reached the

maximum at 10 s and their after being decreased which

indicates the saturation accumulation.

3.3. Influence of pH

The electrochemical oxidation of chalcone was studied with

different supporting electrolytes such as Britton-Robinson

buffer and phosphate buffer. Within the range of pH 3.0 -

11.2, the phosphate buffer gave the good results as com-

pared to other supporting electrolytes. Hence phosphate

buffers were taken as a supporting electrolyte. With in-

creasing the pH of the buffer solution, the peak potential

shifted to less positive values as shown in Figure 2.

The plot of Ep versus pH (Figure 3(a)) shows that the

peak potential is pH dependent. The variation of peak cur-

rent with pH is as shown in Figure 3(b). The peak cur-

rent decreased from pH 3 - 11.2. The voltammetric re-

sponse was markedly dependent on pH. From the experi-

mental results, (Figure 2) it is observed that highest peak

current and better shape of the voltammogram was ob-

served at pH 3.0, suggesting this pH is optimal pH value.

From the plot of current versus pH (Figure 3(b)) it is

evident that current goes on decreasing with increase in

pH. Hence pH variation is restricted to 11.2.

Figure 2. Influence of pH on the shape of the peaks in phos-

phate buffer solution at (a) pH 3.0; (b) pH 4.2; (c) pH 5.0;

(d) pH 6.0; (e) pH 7.0; (f) pH 8.0; (g) pH 9.2; (h) pH 10.4

and (i) pH 11.2. Other conditions are as in Figure 1.

Ep ( V )

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

024681012

(a)

051015

Current x 1 0-4

(b)

Figure 3. (a) Influence of pH on the peak potential of chal-

cone for peaks A and B. Other conditions are as in Figure 1;

(b) Variation of peak currents of peaks A and B with pH.

Other conditions are as in Figure 1.

K. M. NAIK, S. T. NANDIBEWOOR 659

3.4. Influence of Scan Rate

Useful information involving electrochemical mechanism

usually can be acquired from the relationship between peak

current and scan rate. Therefore, the electrochemical be-

havior of chalcone at different scan rates from 50 to 300

m·Vs−1 (Figure 4) was also studied. From this we observed

that increasing the scan rate, the peak potential of A is

shifted to more positive values. Simultaneously, the width

at half-height of peak A increases. It is suggested that this

corresponds to the oxidation of chalcone dimers formed

at the GCE surface. The formation of such kind of dimers

is well documented in the literature [16,17], but they can

only be observed when high scan rates are used probably

because they have short life time.

At the same time, the cathodic peak C is displaced to

more negative values whereas its current increases with

the scan rate. Nevertheless, the fact that peak current of

C is always smaller than the peak current of A suggests

that the oxidation product of chalcone is very unstable

and undergoes hydrolysis in the solution [18].

There is a good linear relationship between peak cur-

rent and scan rate. The equations are

() ()

I10 A4.6745Vs0.7531υ

−−

=−, r0.9821=

, r0.9828=

3,r0.9917==

6,r0.9842==

and

() ()

I10 A5.7583Vs0.8515υ

−−

=−

for peaks A and B, respectively as shown in Figure 5(a).

In addition, there was a linear relation between log Ip and

log υ, corresponding to the following equation:

() ()

log I10A0.4881logVs+0.581υ

−−

and

() ()

log I10A0.516logVs+0.670υ

−− ,

for peaks A and B, respectively (Figure 5(b)). The slope

of 0.4881 and 0.516 is close to the theoretically expected

value of 0.5 for a diffusion controlled process [19].

Figure 4. Cyclic voltammograms of 10 μM chalcone on GCE

with different scan rates, (a) - (f) were 50, 100, 150, 200, 250

and 300 m·Vs–1, respectively. Other conditions are as in Fig-

ure 1.

υ (V/s)

Current × 10

–

0. 00

0. 50

1. 00

1. 50

2. 00

2. 50

3. 00

0.000.10 0.200.30 0.40

log υ (V/s)

(a)

-0. 2

-0. 1

0.1

0.2

0.3

0.4

0.5

-1.5 -1.3 -1.1-0.9 -0.7 -0.5 -0.3 -0.1

log Ip × 10

–4

(b)

0.0

0.4

0.8

1.2

1.6

2.0

-1.6 -1.2-0.8 -0.40.0

(

V/s

)

Ep (V)

()

EV0.5993logVs+1.2974

−

()

pV0.2591 logVs+1.8196

−

()

(c)

Figure 5. (a) Dependence of the oxidation peak current of

peaks A and B on the scan rate; (b) Dependence of the loga-

rithm of peak current on logarithm of scan rate for peaks A

and B; (c) Relationship between peak potential and loga-

rithm of scan rate for the peaks A and B.

The peak potential shifted to more positive values with

increasing the scan rates. The linear relationship between

peak potential and logarithm of scan rate can be expressed

and E,

for the peaks A and B, respectively (Figure 5(c)).

According to the quasi reversible electrode process, Ip

is defined by the following equation [20]:

()

1212 12

ao o

I2.6910nn ADC

αν

=×××××× (2)

where α (alpha) is the transfer coefficient, na the number

K. M. NAIK, S. T. NANDIBEWOOR

660

of electrons transferred, ν (nu) the scan rate, A is the elec-

trode area, Do is the diffusion coefficient and Co is the

concentration of electro active species (10 μM). Thus the

value of Do is taken from the slope of Ip versus ν1/2. In

this system, for peak A, the slope was 3.7 × 10−3. The αna

was calculated according to the following equation:

47.7

nmV

EE−

where Ep/2 is the potential where the current is at half the

peak value. Further, the number of electron (n) transferred

in the electro oxidation of chalcone was calculated to be

2.13 ≈ 2.0.

3.5. Mechanism

In the proposed method the chalcone undergoes oxidation

with two electrons and the possible mechanisms are as

shown in Scheme 2 for peaks A, B and C respectively

which are proposed based on the earlier literature [12].

Based on the kinetic data, the proposed mechanism of

oxidation of chalcone by trichloroisocynuric acid [TClCA]

in HOAc-HClO4 medium [11] is different. Hence the oxi-

dative pathways of electrochemical and chemical proc-

esses are different.

+ H

(a)

+ 2 e

(b)

+ 2 e-+ 2 H+

(c)

Scheme 2. Proposed mechanisms of electrooxidation of chal-

cone for peaks (a), (b) and (c).

3.6. Calibration Curve

In order to develop a voltammetric method for determin-

ing the drug, we selected the differential pulse (DPV) and

square wave voltammetric (SWV) mode, because the peaks

are sharper and better defined at lower concentration of cha-

lcone, than those obtained by cyclic voltammetry, with

low background current, resulting in improved resolution.

According to the obtained results, it was possible to ap-

ply these techniques to the quantitative analysis of chal-

cone. The phosphate buffer solution of pH 3.0 was selected

as the supporting electrolyte for the quantification of cha-

lcone as it gave maximum peak current at pH 3.0. The

peak at about 0.275 V in DPV and 0.26 V in SWV was

considered for the analysis. Differential pulse voltammo-

grams and square wave voltammograms obtained with in-

creasing amount of chalcone showed that the peak cur-

rent increased linearly with increasing concentration, as

shown in Figures 6(a) and (b) .

(a)

(b)

Figure 6. (a) Differential-pulse voltammograms of GCE in

chalcone solution at different concentraions: a: 0.2, b: 1, c:

2, d: 4, e: 6, f: 8 and g: 10 μM. Inset plot of the peak current

against concentration of chalcone; (b) Square wave voltam-

mograms of GCE in chalcone solution at different concen-

trations: a: 0.2, b: 1, c: 2, d: 4, e: 6, f: 8 and g: 10 μM. Inset

plot of the peak current against concentration of chalcone.

K. M. NAIK, S. T. NANDIBEWOOR 661

Using the optimum conditions described above, linear

calibration curves were obtained for chalcone in the range

of 0.2 to 10.0 μM. The linear equation was

() (

IμA72100C0.8606 r0.9832=+ =

)

, C is inμM

)

Cisin 10M

and

() (

I10 A78200C1.7644r0.9726,=+ =

for DPV and SWV respectively. The DPV presents a good

linear response as compared to SWV in view of a less int-

ercept of linear plot of Ip versus concentrations. Deviation

from linearity was observed for more concentrated solu-

tions, due to the adsorption of oxidation product on the

electrode surface. It was also observed that the peak po-

tential (Ep) and half peak potential (Ep/2) were shifted tow-

ards more positive value suggesting that product under-

goes adsorption at the surface of GCE. Related statistical

data of the calibration curves were obtained from five dif-

ferent calibration curves. The limit of detection (LOD) and

quantification (LOQ) were 0.18 μM and 0.6 μM, respec-

tively. The LOD and LOQ were calculated using the fol-

lowing equations:

LOD3, LOQ10

msm==

where s is the standard deviation of the peak currents of

the blank (five runs) and m is the slope of the calibration

curve.

3.7. Stability and Reproducibility

In order to study the stability and reproducibility of the

electrode, a 10 μM chalcone solution were measured within

the same electrode (renewed every time) for every several

hours within day, the RSD of the peak current was 2.88%

(number of measurements = 5). As to the between day re-

producibility, it was similar to that of within a day if the

temperature was kept almost unchanged which could be

attributed to the excellent stability and reproducibility of

GCE.

3.8. Effect of Surfactant

Surfactants even in trace quantities can exert a strong ef-

fect on the electrode process. Adsorption of such substances

at the electrode may inhibit the electrolytic process, bring

about the irregularity in the voltammograms, and shift in

the wave to more negative potentials [21,22].

Surface-active substances have the common tendency

of accumulation at interfaces. The lack of affinity between

the hydrophobic portion of the surfactant and water leads

to a repulsion of these substances from the water phase

as a consequence of reduction of the microscopic chal-

cone water interface. Experimental results showed that

the addition of cationic surfactant, cetyltrimethylammo-

nium bromide, as anionic surfactant, sodiumdodecyl sul-

fate and the non-ionic surfactant, Triton X-100 have no

much influence on the peak current and peak potential.

3.9. Effect of Interferents

For the analytical applications of the proposed method, the

effect of potential interferents that are likely to be in bio-

logical samples were evaluated under the optimum experi-

mental conditions. Differential-pulse voltammetric experi-

ments were carried out for 1.0 μM chalcone in the pres-

ence of 1.0 mM of each of the interferents. The experimen-

tal results (Table 1) showed that thousand-fold excess of

glucose, starch, sucrose, dextrose, gum acacia, citric acid,

tartaric acid and oxalic acid did not interfere with the volt-

ammetric signal of chalcone. Therefore, the proposed meth-

od can be used as a selective method.

3.10. Detection of Chalcone in Spiked Human

Plasma Samples

The developed differential-pulse voltammetric method for

the chalcone determination was applied to spiked human

plasma samples. The recoveries from human plasma were

measured by spiking drug free plasma with known amounts

of chalcone. The plasma samples were prepared as de-

scribed in experimental section. A quantitative analysis can

be carried out by adding the standard solution of chalcone

into the detect system of plasma sample. The calibration

graph was used for the determination of spiked chalcone

in plasma samples. The results of four plasma samples

obtained are listed in Table 2. The recovery determined

was in the range from 98.0% to 103.0% and the RSD was

2.05%.

Table 1. Influence of potential interferents on the voltam-

metric response of 1.0 μM chalcone.

Interferent Concentration (mM) Signal change (%)

Glucose 1.0 −1.6

Starch 1.0 −1.2

Sucrose 1.0 −1.6

Dextrose 1.0 −1.6

Citric acid 1.0 −1.2

Tartaric acid 1.0 −1.6

Oxalic acid 1.0 −1.2

Gum acacia 1.0 −1.6

Table 2. Determination of chalcone in spiked human plasma

samples.

Human

plasma Spiked (μM) Detection(a)

(μM) Recovery (%)SD ± RSD

(%)

Sample 1 0.3 0.3046 98.17 0.0011 ± 3.83

Sample 2 0.7 0.7003 99.59 0.0079 ± 1.13

Sample 3 3.0 2.8981 103.19 0.0092 ± 3.17

Sample 4 7.0 6.941 100.04 0.0057 ± 0.82

(a)Mean average of five determinations.

K. M. NAIK, S. T. NANDIBEWOOR

662

Table 3. Determination of chalcone in urine samples.

Urine Spiked (μM) Detected(a) (μM) Recovery (%) SD ± RSD (%)

Sample 1 0.3 0.2946 101.22 0.0014 ± 4.89

Sample 2 0.7 0.6773 103.03 0.0180 ± 2.65

Sample 3 3.0 3.001 99.75 0.0144 ± 0.47

Sample 4 7.0 7.123 98.98 0.0757 ± 1.07

(a)Mean average of five determinations.

3.11. Detection of Chalcone in Urine Samples

The applicability of the DPV to the determination of chal-

cone in spiked urine was investigated. The recoveries from

urine were measured by spiking drug free urine with known

amounts of chalcone. The urine samples were diluted 100

times with the phosphate buffer solution before analysis

without further pretreatments. A quantitative determina-

tion can be carried out by adding the standard solution of

chalcone into the detect system of urine sample. The cali-

bration graph was used for the determination of spiked

chalcone in urine samples. The detection results of four

urine samples obtained are listed in Table 3. The recov-

ery determined was in the range from 98.0% to 103.0%

and the R.S.D. was 2.77%. Thus, satisfactory recoveries

of the analyte from the real samples and a good agree-

ment between the concentration ranges studied and the

real ranges encountered in the urine samples when treated

with the drug make the developed method applicable in

clinical analysis.

4. Conclusion

A glassy carbon electrode was used first time for the oxi-

dation of chalcone in phosphate buffer solution. When the

potential was made to move, chalcone produced two an-

odic and one cathodic peak at about 0.513 V, 1.478 V

and −0.689 V in pH 3.0 phosphate buffer, respectively. A

suitable mechanism was proposed. The peak at about 0.51

V was suitable for analysis and the peak current was lin-

ear to chalcone concentrations over a certain range under

the selected conditions. This method can be used for volt-

ammetric determination of selected analyte as low as 0.18

μM with good reproducibility. The proposed method of-

fered the advantages of accuracy and time saving as well

as simplicity of reagents and apparatus. In addition, the

results obtained in the analysis of chalcone in spiked

human plasma and urine samples demonstrated the ap-

plicability of the method for real sample analysis.

5. Acknowledgements

One of the authors, Keerti M. Naik, acknowledges Dr. B.

E. Kumara Swamy, Department of Industrial Chemistry,

Kuvempu University, Shankaraghatta, India for useful dis-

cussions.

REFERENCES

[1] C. L. Ye, J. W. Liu, D. Z. Wei, Y. H. Lu and F. Qian, “In

Vitro Anti-Tumor Activity of 2, 4-Dihydroxy-6-methoxy-3,

5-Dimethylchalcone against Six Established Human Can-

cer Cell Lines,” Pharmacological Research, Vol. 50, No.

5, 2004, pp. 505-510. doi:10.1016/j.phrs.2004.05.004

[2] O. V. Yarishkin, W. R. Hyung, P. Jae-Yong, S. Y. Min, H.

Seong-Geun and H. P. Ki, “Sulfonate Chalcone as New

Class Voltage-Dependent K+ Channel Blocker,” Bioor-

ganic & Medicinal Chemistry Letters, Vol. 18, No. 1,

2008, pp. 137-140. doi:10.1016/j.bmcl.2007.10.114

[3] L. Ni, C. Q. Meng and J. A. Sikorski, “Recent Advances

in Therapeutic Chalcones,” Expert Opinion on Therapeu-

tic Patents, Vol. 14, No. 12, 2004, pp. 1669-1691.

doi:10.1517/13543776.14.12.1669

[4] B. Uslu and S. A. Ozkan, “Electrochemical Characterisa-

tion of Nefazodone Hydrochloride and Voltammetric De-

termination of the Drug in Pharmaceuticals and Human

Serum,” Analytica Chimica Acta, Vol. 462, No. 1, 2002,

pp. 49-57. doi:10.1016/S0003-2670(02)00280-5

[5] J. M. Kauffmann, M. P. Prete, J. C. Vire, G. J. Patriarche

and Fresenius, “Voltammetry of Pharmaceuticals Using

Different Types of Modified Electrodes,” Fresenius’

Journal of Analytical Chemistry, Vol. 321, No. 2, 1985,

pp. 172-176. doi:10.1007/BF01117759

[6] F. Belal, H. Abdinic and N. Zoman, “Voltammetric De-

termination of Nilvadipine in Dosage Forms and Spiked

Human Urine,” Journal of Pharmaceutical and Biomedi-

cal Analysis, Vol. 26, No. 4, 2001, pp. 585-592.

doi:10.1016/S0731-7085(01)00485-X

[7] P. Zuman, “Current Status of Polarography and Voltam-

metry in Analytical Chemistry,” Analytical Letters, Vol.

33, No. 2, 2000, pp. 163-174.

doi:10.1080/00032710008543044

[8] T. B. Demircigil, S. A. Ozkan, O. Coruh and S. Yilmaz,

“Electrochemical Behaviour of Formoterol Fumarate and

Its Determination in Capsules for Inhalation and Human

Serum Using Differential Pulse and Square Wave Volt-

ammetry,” Electroanalysis, Vol. 14, No. 2, 2002, pp. 122-

127.

doi:10.1002/1521-4109(200201)14:2<122::AID-ELAN12

2>3.0.CO;2-1

[9] S. A. Kumar, C. F. Tang and S. M. Chen, “Poly (4-

Amino-1-1’-azobenzene-3,4’-disulfonic Acid) Coated Elec-

trode for Selective Detection of Dopamine from Its Inter-

ferences,” Talanta, Vol. 74, No. 4, 2008, pp. 860-866.

doi:10.1016/j.talanta.2007.07.015

[10] V. C. Diculescu, S. Kumbhat and A. M. O. Brett, “Elec-

trochemical Behaviour of Isatin at a Glassy Carbon Elec-

trode,” Analytica Chimica Acta, Vol. 575, No. 2, 2006, pp.

190-197. doi:10.1016/j.aca.2006.05.091

[11] J. A. Kumar and S. Sondu, “Kinetics and Mechanism of

Oxidation of Chalcones by Ti-Ichloroisocyanuric Acid

[TCICA] in HOAc-HClO4 Medium,” Indian Journal of

Chemistry, Vol. 46A, 2007, pp. 1792-1795.

[12] A. Shah, A. Khan, R. Qureshi, F. Ansari, M. Nazar and S.

Shah, “Redox Behavior of Anticancer Chalcone on a

Glassy Carbon Electrode and Evaluation of Its Interaction

K. M. NAIK, S. T. NANDIBEWOOR

663

Parameters with DNA,” International Journal of Mo-

lecular Sciences, Vol. 9, No. 8, 2008, pp. 1424-1434.

doi:10.3390/ijms9081424

[13] G. D. Christian and W. C. Purdy, “Residual Current in

Orthophosphate Medium,” Journal of Electroanalytical

Chemistry, Vol. 3, No. 6, 1962, pp. 363-367.

doi:10.1016/0022-0728(62)80012-6

[14] B. Rezaei and S. Damiri, “Voltammetric Behavior of

Multi-Walled Carbon Nanotubes Modified Electrode-

Hexacyanoferrate(II) Electrocatalyst System as a Sensor

for Determination of Captopril,” Sensors and Actuators B:

Chemical, Vol. 134, No. 1, 2008, pp. 324-331.

doi:10.1016/j.snb.2008.05.004

[15] B. Eswarappa, B. S. Sherigara and B. E. K. Swamy,

“Electrochemical Investigation of Benzelidene Benzyl

Hydrazide and Its Derivative Shciff Bases at Glassy Car-

bon Electrode,” Bulletin of Electrochemistry, Vol. 20,

2004, pp. 1-6.

[16] A. M. Oliveira Brett, V. Diculeseu and J. A. P. Piedade,

“Electrochemical Oxidation Mechanism of Guanine and

Adenine Using a Glassy Carbon Microelectrode,” Bio-

electrochemistry, Vol. 55, No. 1-2, 2002, pp. 61-62.

doi:10.1016/S1567-5394(01)00147-5

[17] R. N. Goyal and A. Sangal, “Electrochemical Investiga-

tions of Adenosine at Solid Electrodes,” Journal of Elec-

troanalytical Chemistry, Vol. 521, No. 1-2, 2002, pp. 72-

80. doi:10.1016/S0022-0728(02)00645-9

[18] R. N. Goyal, A. Kumar and A. Mittal, “Oxidation Chem-

istry of Adenine and Hydroxyadenines at Pyrolytic Graph-

ite Electrodes,” Journal of the Chemical Society, Perkin

Transactions, Vol. 2, No. 9, 1991, pp. 1369-1375.

[19] D. K. Gosser, “Cyclic Voltammetry: Simulation and

Analysis of Reaction Mechansims,” Vancouver Coastal

Health, New York, 1993

[20] A. J. Bard and L. R. Faulkner, “Electrochemical Methods

Fundamentals and Applications,” 2nd Edition, Wiley,

Hoboken, 2004.

[21] J. Herovsky and J. Rute, “Principles of Polarography,”

Academic Press, New York, 1966.

[22] E. Niranjana, R. R. Naik, B. E. K. Swamy, B. S. Sheri-

gara and H. Jayadevappa, “Studies on Adsorption of Tri-

ton X-100 at Carbon Paste and Ceresin Wax Carbon Paste

Electrodes and the Enhancement Effect in Dopamine

Oxidation by Cyclic Voltammetry,” International Journal

of Electrochemical Science, Vol. 2, 2007, pp. 923-934.

Abbreviations

CV: Cyclic voltammetry; DPV: Differential pulse volt-

ammetry; SWV: Square wave voltammetry; n: Number

of electrons transferred; Ipa: Anodic peak current; D0: Dif-

fusion coefficient; A0: Surface area of the electrode; υ:

Scan rate; C0: Concentration; T: Absolute temperature; R:

Gas constant; F: Faradays constant; Ep: Peak potential; α:

Transfer coefficient; LOD: Limit of detection; LOQ: Limit

of quantification; RSD: Relative standard deviation.