Pencil graphite electrode as an electrochemical sensor for the voltammetric determination of chlorpromazine

1 , PGE showed good sensitivity and increased peak current when compared to alanine and glycine modi ﬁed PGEs in 0.1 mM CPZ (potential window 0 e1.2 V).. Thus, the PGE showed more desira[r]

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Original Article

H.T Purushothama, Y Arthoba Nayaka*, M.M Vinay, P Manjunatha, R.O Yathisha,

K.V Basavarajappa

Department of Chemistry, School of Chemical Science, Kuvempu University, Shankaraghatta, 577451, Shimoga, Karnataka, India

a r t i c l e i n f o Article history:

Received 29 January 2018 Received in revised form 15 March 2018 Accepted 23 March 2018 Available online April 2018

Keywords: Chlorpromazine Cyclic voltammetry

Differential pulse voltammetry Electrochemical sensor Pencil graphite electrode

a b s t r a c t

A selective, simple and sensitive electrochemical sensor has been developed using pencil leads (pencil graphite electrode, PGE) for the investigation of chlorpromazine (CPZ) The cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques were employed to study the anodic behaviour of CPZ The bare PGE showed good electrocatalytic activity towards the determination of CPZ in comparison with alanine and glycine modified PGEs The PGE showed a well enhanced peak current compared to alanine and glycine modified PGEs for the determination of CPZ The electroactive surface area, influence of pH, effect of scan rate, electron transfer kinetics and sensitivity have been studied DPV has shown good linearity in the concentration range of 0.01 mMe 0.08mM with the limit of detection of 0.003mM The proposed sensor has been successfully employed for the determination of CPZ present in a pharmaceutical sample

© 2018 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

1 Introduction

A phenothiazine class of drug, chlorpromazine (CPZ, 2-chloro-10-(3-dimethylaminoprophyl) phenothiazine), has been widely used to treat major depressive illness, bipolar disorder and also for schizophrenia [1] CPZ reacts by blocking postsynaptic dopami-nergic D2receptors in the mesolimbic and prefrontal cortex regions

of the brain and acts as a competitive antagonist of dopamine The blockade of D2receptor is responsible for decreasing the positive

symptoms of schizophrenia[2] Over dosage or excess concentra-tion which may causes several problems such as interpalpebral conjunctiva, abnormal pigmentation of eyelids, tract disorders, and cataract and accommodation interference[3] Thus, emerging and accurate analytical method for detecting chlorpromazine became an important topic of research

Various analytical methods have been reported on the inves-tigation of CPZ such as gas chromatography [4,5], spectropho-tometry [6e8], HPLC [9,10], chemiluminescence [11e13], electrochemical methods potentiometry[14,15], polarography[16]

and capillary zone electrophoresis[17] Although chromatographic and spectrophotometric methods are widely used for the deter-mination of CPZ, the instruments involved are often costly to run and maintain, and the pretreatment process for samples is usually time-consuming and complicated Among these, the analytical methods based on electrochemical sensors exhibited distinctive and unique properties such as rapid response, inexpensive, simple operation procedure, time saving, high selectivity and sensitivity [18e24] The various electrodes have been employed for the determination of CPZ, such as, carbon paste electrode (CPE)[18], boron-doped diamond electrode (BDDE) [3], glassy carbon elec-trode (GCE)[19], graphene paste electrode (GPE)[20]and ruthe-nium electrodes[21]

Among various carbon based electrodes, pencil graphite elec-trodes (PGEs) have widespread attention due to their sp2 hybrid-ized carbon which shows good adsorption, conductivity, high sensitivity, smaller background current, and ease of preparation and surface modiﬁcation properties[25,26] As compared to the other electrodes such as glassy carbon electrode, the renewal of surface plays an important role for subsequent analysis because of electrochemical reactions of the molecule may cause a change in surface properties of the electrode[27] Thus subsequent renewal of surface of the PGE for the each trial may lead to the selective and

* Corresponding author Fax: þ91 08282 256255 E-mail address:drarthoba@yahoo.co.in(Y.A Nayaka)

Peer review under responsibility of Vietnam National University, Hanoi

Contents lists available atScienceDirect

Journal of Science: Advanced Materials and Devices j o u r n a l h o m e p a g e : w w w e l s e v i e r c o m / l o c a t e / j s a m d

https://doi.org/10.1016/j.jsamd.2018.03.007

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sensitive electrochemical investigation of chlorpromazine In this work, the sensitive and selective determination of CPZ presented in pharmaceutical formulations using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods has been carried out using PGEs To the best of our knowledge, no literature has been found on this research direction

2 Experimental

2.1 Chemicals, reagents and instrumentation

All the chemicals were of analytical grade and used without any further puriﬁcation CPZ was procured from Tokyo Chemical In-dustry Co., Ltd K2HPO4, KH2PO4 and KCl were procured from

Merck, Mumbai, India Potassium ferricyanide was procured from HiMedia Laboratories Pvt Ltd The Equiptronics pH meter (EQ - 611) was used to measure pH of the solution Pencil graphite leads of 0.5 mm diameter and length of 60 mm were procured from Kokuyo Camlin Ltd., Mumbai, India EMETIL-25 tablets were procured from local pharmaceutical shop Doubly distilled water was used for the preparation of solutions All the electrochemical measurements were carried out using electrochemical workstation CHI660D (CH Instruments, USA) using three electrode system The PGE was used as working electrode Saturated calomel and platinum wire were used as reference and counter electrodes, respectively

2.2 Preparation of pencil graphite electrode

The HB pencil lead of 0.5 mm diameter and length of 60 mm was used as PGE for the investigation of CPZ The electrical contact has been made at one end of the pencil lead using copper wire and it was inserted into the plastic tube containing araldite mixture (epoxy resin, 1:1) After 24 h of drying, the edge of the PGE was renewed by using sharp blade and then smoothened using emery paper followed by butter sheet

After preparing the PGE, it has been electro-polymerized using alanine and glycine within the potential window 0e0.2 V (50 cycles)

3 Results and discussion

3.1 Cyclic voltammetric study of chlorpromazine on PGE

Voltammetric methods such as CV and DPV were employed to evaluate the electrochemical behaviour of CPZ Electrochemical behaviour of 0.1 mM CPZ was investigated in phosphate buffer solution (at pH-7) with the scan rate of 0.1 Vs1 InFig 1, PGE showed good sensitivity and increased peak current when compared to alanine and glycine modified PGEs in 0.1 mM CPZ (potential window 0e1.2 V) At PGE the anodic peak current is 3.16mA at 0.759 V which was higher than that of alanine (2.19mA) and glycine (2.30mA) modified PGEs with the small shift in the positive potential (0.770 and 0.761 V) Thus, the PGE showed more desirable electrochemical response compared to alanine and glycine modified PGEs In conclusion, PGE showed good conduc-tivity, sensiconduc-tivity, selectivity and electron transfer kinetics compared to alanine and glycine modified PGE for the electro-chemical investigation of CPZ

3.2 Study of electroactive surface area of PGE

The electrocatalytic activity of PGE can be studied by calculating the electroactive surface area of the electrode The cyclic voltam-mograms of [Fe(CN)6]3/4redox system has been probed to

different scan rates and for reversible processes, the Randles-Sevick

equation has been used to calculate electroactive surface area of the electrode[28]:

Ip¼ 2:69 105n 2AD

1 0C0v

1

Where Ipis anodic peak current (mA), n indicates the number of

electrons transferred (n¼ for K3[Fe(CN)6]), A is the surface area of

the electrode (cm2), D

0 is the diffusion coefﬁcient

(D0¼ 7.6 106cm2s1for K3[Fe(CN)6]), C0*is the concentration of

electroactive species (mol cm3), andnis the scan rate (V s1) By plotting Ipavs.n1/2the value of diffusion coefﬁcient can be obtained

On substituting these values in the above equation, the electro-active surface area was found to be 6.85 cm2on PGE

3.3 Effect of solution pH

The anodic behaviour of CPZ on PGE at different pH values was studied using CV As shown in theFig 2, the anodic peak current increases as increasing pH of the solution from pH 2.0 to 7.0 The better current response and well deﬁned voltammogram shape observed at pH 7.0 Further increase in pH from pH 8.0 to 9.0 results in a decrease in the peak current Hence, pH 7.0 was chosen as optimum pH for the further investigation.Scheme 1shows possible oxidation mechanism of CPZ

3.4 Study on effect of scan rate

The electrode reaction (diffusion or adsorption) processes were carried out by varying the scan rate The effect of scan rate on the electrochemical response of CPZ at PGE in 0.1 M PBS of pH 7.0 was recorded by CV method as shown inFig 3a As scan rate increased from 25 to 200 mVs1there was a small shifts in the peak potential with linear increase of peak current The small shift in positive potential is due to the adsorption or double layer formation at the surface of the electrode which shows an irreversible nature of the electroactive molecule The linear regression equation between the peak current (Ipa) vs scan rate (n) expressed as Ipa

(mA)¼ 2.12568 106ỵ 1.15029 108n(V s1) For the plot of Ipa

vs n1/2, the linear regression equation expressed as Ipa

(mA)ẳ 1.21966 106ỵ 2.1588 107n1/2(V s1) The above result

indicates that the process is diffusion controlled

0.4 0.6 0.8 1.0 1.2

-3.2 -3.0 -2.8 -2.6 -2.4 -2.2 -2.0 -1.8

ALANINE PGE GLYCINE PGE

Potential (V)

Cu

rren

t

(

μ

A

)

PGE

(3)

The linear regression equation for log Ipavs lognwas given by

the equation: log Ipa (mA) ẳ 6.00137 ỵ 0.26711 log n (V s1)

(Fig 3d) The slope value of 0.26 gives an ideal reaction condition for diffusion controlled process[29] Thus the anodic behaviour of CPZ exhibits diffusion controlled process

For an irreversible anodic reaction, the standard rate constant (k0) can be calculated by Laviron equation[30]:

Epẳ E0ỵ

2:303RT anF

log

RTk0

anF

ỵ

2:303RT anF

logv

where, E0refers to formal potential, R indicates the universal gas constant, T is the absolute temperature,agives the electron transfer co-efﬁcient, F indicates Faradays constant

The‘an’ value has been calculated from the slope of Epvs logn

The linear regression equation is given as Ep

(V)ẳ 0.66374 ỵ 0.04825 logn(V s1); r¼ 0.9955 In this experi-ment the slope value for peak a was found to be 0.0482 By substituting T¼ 298 K, R ¼ 8.314, and F ¼ 96485,an value was found to be 0.7156 and 0.9324 For irreversible electrode reaction,a value is 0.5 Thus, the number of electrons involved in electro-chemical reaction was found to be for both the peaks The intercept of Epvs logncurve is 0.66374 and the value of k0is found

to be 15.03ms1

3.5 Analytical application of CPZ

The quantitative estimation of CPZ was studied by using the DPV technique DPV has got more prominence compared to CV due to its sensitivity and low background current[30e32] In the linear concentration range from 0.01 mM to 0.08 mM, the con-centration of CPZ increases with increase in peak current as shown in theFig 4a The linear regression equation is: Ipa(mA)¼

1.37127 108 Mỵ 2.66543 107; r2ẳ 0.9955 The limit of detection (LOD) value can be calculated using the formula, LOD¼ S/m and found to be 3.002 nM.Table 1gives the reported and experimentally determined LOD values of CPZ Thus the

N

S

Cl CH2CH2CH2N(CH3)2

-e-

+e-N+

S

Cl CH2CH2CH2N(CH3)2

-e-N+

S+

Cl CH2CH2CH2N(CH3)2

-H2O N

S

Cl CH2CH2CH2N(CH3)2

O +

2H+

Chlorpromazine

Scheme Structure and possible mechanism of CPZ

0.4 0.6 0.8 1.0 1.2

-1.0 -0.8 -0.6 -0.4 -0.2 0.0

pH: 7.0

Potential (V)

Cu

rren

t

(

μ

A

)

(a)

1 2 3 4 5 6 7 8 9 10

0.16 0.18 0.20 0.22 0.24 0.26

Curr

ent

(μ

Α

)

pH

(b)

(4)

proposed electrode has been proven to be better sensor compared to other carbon based electrodes

3.6 Pharmaceutical analysis

The analysis of CPZ present in tablet sample (EMETIL-25) was studied by using differential pulse voltammetric method Standard addition method was used to investigate CPZ in tablet samples Suitable amount of CPZ tablets were grounded to get afine powder and dissolved in phosphate buffer solution (0.1 M) The obtained solution was sonicated for about 10 andfiltered using what-manfilter paper Finally, the resultant filtrate was transferred into 50 ml volumetric flask and diluted upto the mark Further, the required amount of sample solution was taken for anlaysis Differ-ential pulse voltammograms were recorded after the addition of known concentration of CPZ to tablet solutions as shown inFig Table 2shows the recovery result of CPZ in tablet samples which found in the range of 99%e100% Hence, the obtained results show

that PGE could be applied successfully for the detection of CPZ in pharmaceutical tablets

4 Conclusion

The anodic behaviour of CPZ was successfully investigated by using PGE PGE showed the good peak current enhancement in comparison with Alanine and Glycine modiﬁed PGE's Among CPE (carbon paste electrode), BDDE (Boron doped diamond electrode), GCE (glassy carbon electrode) and other modiﬁed electrodes, the PGE showed the good electrocatalytic activity towards the oxidation of CPZ The developed PGE shows a low limit of detection, a wide potential range, selectivity, sensitivity and reliability Thus, the proposed electrochemical method is simpler, less time consuming, and shows a good practical appli-cability in determination of CPZ with acceptable percentage re-covery This method can thus be applied for real samples analysis

0.2 0.4 0.6 0.8 1.0 1.2

-4.5 -4.0 -3.5 -3.0 -2.5 -2.0

(a) h

Potential (V)

Current

(

μ

A

)

a

4 6 8 10 12 14

2.5 3.0 3.5 4.0 4.5 5.0

(b)

Current

(

μ

A

)

Square(ν)

20 40 60 80 100 120 140 160 180 200 220 2.5

3.0 3.5 4.0 4.5 5.0

(c) Scan rate (ν)

Cu

rren

t

(

μ

A

)

1.4 1.6 1.8 2.0 2.2 2.4

-5.60 -5.55 -5.50 -5.45 -5.40 -5.35 -5.30

(d)

log Ip

logν

(5)

Acknowledgements

The authors are grateful to the University Grant Commission-Basic Scientiﬁc Research, New Delhi, India for providing ﬁnancial assistance and DST (SERB) for providing the instrumental facility References

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Table

Reported experimental values of CPZ using different carbon based electrodes Electrode Analytical

technique

pH Linear range (mM L1)

LODa (mM L1)

Reference

MGEb CVc 9.0 0.6e10.0 0.1 [33]

GPEd DPVe 4.0 0.01e9.0 0.006 [34]

CPEf SWVg 7.0 0.1e350 0.07 [24]

BDDEh DPV 4.0 0.1e40 3 [35]

GCEi DPV 7.0 0.019e9.2 1.3 [1]

PGEj DPV 7.0 0.01e0.08 0.003 Present work

aLimit of detection. b Modiﬁed gold electrode. c Cyclic voltammetry. d Graphene paste electrode. e Differential pulse voltammetry.

f Carbon paste electrode. g Square wave voltammetry. hBoron doped diamond electrode.

i Glassy carbon electrode. j Pencil graphite electrode.

e a

Concentration / μM

Current /

μ

A

Fig Determination of CPZ in the EMETIL-25 tablet using the standard addition method (a) 0.07mM (tab) (b) 0.08mM (tab)ỵ 1mM (std) (c) 0.08mM (tab)ỵ 2mM (std) (d) 0.08mM (tab)ỵ 3mM (std) and (e) 0.08mM (tab)ỵ 1mM (std)

Table

Results obtained from detection of CPZ in pharmaceutical tablets

Technique Tablet sample Added (mM L1) Found (mM L1) Recovery (%)

DPVa 1 0.07 0.07± 0.1 99.99

2 0.08 0.08± 0.1 100

aDifferential Pulse Voltammetry.

0.6 0.7 0.8 0.9 1.0

-0.12 -0.10 -0.08 -0.06 -0.04 -0.02 0.00

(viii) (i)

Cu

rrent

(

μ

A

)

Concentration (μM)

(a)

0.01 0.02 0.03 0.04 0.05 0.06

0.020 0.025 0.030

(b) R2 = 0.9955

Concentration (μM)

Current

(

μ

A

)

(6)

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