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

Journal of Science: Advanced Materials and Devices (2018) 161e166 Contents lists available at ScienceDirect Journal of Science: Advanced Materials and Devices journal homepage: www.elsevier.com/locate/jsamd Original Article Pencil graphite electrode as an electrochemical sensor for the voltammetric determination of chlorpromazine 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 a b s t r a c t Article history: Received 29 January 2018 Received in revised form 15 March 2018 Accepted 23 March 2018 Available online April 2018 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 mM e 0.08 mM with the limit of detection of 0.003 mM 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/) Keywords: Chlorpromazine Cyclic voltammetry Differential pulse voltammetry Electrochemical sensor Pencil graphite electrode Introduction A phenothiazine class of drug, chlorpromazine (CPZ, 2-chloro10-(3-dimethylaminoprophyl) phenothiazine), has been widely used to treat major depressive illness, bipolar disorder and also for schizophrenia [1] CPZ reacts by blocking postsynaptic dopaminergic D2 receptors in the mesolimbic and prefrontal cortex regions of the brain and acts as a competitive antagonist of dopamine The blockade of D2 receptor is responsible for decreasing the positive symptoms of schizophrenia [2] Over dosage or excess concentration 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 investigation of CPZ such as gas chromatography [4,5], spectrophotometry [6e8], HPLC [9,10], chemiluminescence [11e13], electrochemical methods potentiometry [14,15], polarography [16] * 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 and capillary zone electrophoresis [17] Although chromatographic and spectrophotometric methods are widely used for the determination 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 electrode (GCE) [19], graphene paste electrode (GPE) [20] and ruthenium electrodes [21] Among various carbon based electrodes, pencil graphite electrodes (PGEs) have widespread attention due to their sp2 hybridized 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 https://doi.org/10.1016/j.jsamd.2018.03.007 2468-2179/© 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/) 162 H.T Purushothama et al / Journal of Science: Advanced Materials and Devices (2018) 161e166 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 2.1 Chemicals, reagents and instrumentation All the chemicals were of analytical grade and used without any further purification CPZ was procured from Tokyo Chemical Industry 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 -2.0 Current (μA) Experimental -1.8 -2.2 ALANINE PGE GLYCINE PGE -2.4 -2.6 -2.8 PGE -3.0 -3.2 0.4 0.8 1.0 1.2 Potential (V) Fig Cyclic voltammogram of 0.1 mM CPZ at alanine PGE, glycine PGE and PGE with pH of 7.0, scan rate of 100 mVsÀ1 equation has been used to calculate electroactive surface area of the electrode [28]: Ip ¼ 2:69 Â 105 n2 AD20 C0Ã v2 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) 0.6 Where Ip is anodic peak current (mA), n indicates the number of electrons transferred (n ¼ for K3 [Fe(CN)6]), A is the surface area of the electrode (cm2), D0 is the diffusion coefficient (D0 ¼ 7.6 Â 10À6 cm2 sÀ1 for K3 [Fe(CN)6]), C0* is the concentration of electroactive species (mol cmÀ3), and n is the scan rate (V sÀ1) By plotting Ipa vs n1/2 the value of diffusion coefficient can be obtained On substituting these values in the above equation, the electroactive surface area was found to be 6.85 cm2 on PGE 3.3 Effect of solution pH 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 VsÀ1 In Fig 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 3.16 mA at 0.759 V which was higher than that of alanine (2.19 mA) and glycine (2.30 mA) 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 conductivity, sensitivity, selectivity and electron transfer kinetics compared to alanine and glycine modified PGE for the electrochemical 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 voltammograms of [Fe(CN)6]3À/4Àredox system has been probed to different scan rates and for reversible processes, the Randles-Sevick The anodic behaviour of CPZ on PGE at different pH values was studied using CV As shown in the Fig 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 shows 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 in Fig 3a As scan rate increased from 25 to 200 mVsÀ1 there 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) ẳ 2.12568 106 ỵ 1.15029 Â 10À8 n (V sÀ1) For the plot of Ipa vs n1/2, the linear regression equation expressed as Ipa (mA) ẳ 1.21966 106 ỵ 2.1588 107 n1/2(V s1) The above result indicates that the process is diffusion controlled H.T Purushothama et al / Journal of Science: Advanced Materials and Devices (2018) 161e166 -0.4 The linear regression equation for log Ipa vs log n was given by the equation: log Ipa (mA) ẳ 6.00137 ỵ 0.26711 log n (V sÀ1) (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]: -0.6 Ep ¼ E0 þ -0.8 where, E0 refers to formal potential, R indicates the universal gas constant, T is the absolute temperature, a gives the electron transfer co-efficient, F indicates Faradays constant The ‘an’ value has been calculated from the slope of Ep vs log n The linear regression equation is given as Ep (V) ẳ 0.66374 ỵ 0.04825 log n (V s1); r ¼ 0.9955 In this experiment the slope value for peak a was found to be 0.0482 By substituting T ¼ 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 electrochemical reaction was found to be for both the peaks The intercept of Ep vs log n curve is 0.66374 and the value of k0 is found to be 15.03 msÀ1 (a) 0.0 Current (μA) -0.2 pH: 7.0  -1.0 0.4 0.6 0.8 1.0 1.2 Potential (V) 0.26 (b) 0.24 Current (μΑ) 163 0.22 0.20      2:303RT RTk0 2:303RT log ỵ log v anF anF anF 3.5 Analytical application of CPZ 0.18 0.16 10 pH Fig (a) The variation of the peak current vs potential (a) and pH (b) for the mM CPZ in 0.1 M phosphate buffer solution CH 2CH 2CH 2N(CH 3)2 CH 2CH 2CH 2N(CH 3)2 + Cl N 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 concentration of CPZ increases with increase in peak current as shown in the Fig 4a The linear regression equation is: Ipa (mA) ¼ 1.37127 Â 10À8 M þ 2.66543 Â 10À7; r2 ¼ 0.9955 The limit of detection (LOD) value can be calculated using the formula, LOD ¼ S/m and found to be 3.002 nM Table gives the reported and experimentally determined LOD values of CPZ Thus the Cl N -e+e- S S Chlorpromazine -e- CH 2CH 2CH 2N(CH 3)2 N 2H + + CH 2CH 2CH 2N(CH 3)2 + Cl -H 2O N + S S O Scheme Structure and possible mechanism of CPZ Cl 164 H.T Purushothama et al / Journal of Science: Advanced Materials and Devices (2018) 161e166 proposed electrode has been proven to be better sensor compared to other carbon based electrodes that PGE could be applied successfully for the detection of CPZ in pharmaceutical tablets 3.6 Pharmaceutical analysis Conclusion 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 a fine powder and dissolved in phosphate buffer solution (0.1 M) The obtained solution was sonicated for about 10 and filtered using whatman filter 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 Differential pulse voltammograms were recorded after the addition of known concentration of CPZ to tablet solutions as shown in Fig Table shows the recovery result of CPZ in tablet samples which found in the range of 99%e100% Hence, the obtained results show 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 applicability in determination of CPZ with acceptable percentage recovery This method can thus be applied for real samples analysis 5.0 -2.0 4.5 a Current (μA) Current (μA) -2.5 -3.0 -3.5 -4.0 4.0 3.5 3.0 h -4.5 0.2 0.4 (a) 0.6 0.8 1.0 2.5 1.2 (b) 10 Square (ν) 5.0 -5.30 4.5 -5.35 12 14 -5.40 4.0 log Ip Current (μA) Potential (V) 3.5 -5.45 -5.50 3.0 -5.55 2.5 (c) 20 40 60 80 100 120 140 160 180 200 220 Scan rate (ν) -5.60 (d) 1.4 1.6 1.8 2.0 2.2 2.4 log ν Fig Voltammograms of 0.1 mM CPZ in 0.l PBS (pH 7.0) at various scan rates (a) Curve a to h gives the scan rates of 25 mV SÀ1 to 200 mV SÀ1; (b) Linear plot of anodic peak currents verses square root of scan rates; (c) Linear plot of anodic peak currents verses the scan rates; (d) Linear plot of logarithmic anodic peak currents verses the logarithmic scan rates H.T Purushothama et al / Journal of Science: Advanced Materials and Devices (2018) 161e166 165 0.00 -0.02 (i) -0.06 (viii) -0.08 a Current / μA Current (μA) -0.04 e -0.10 (a) -0.12 0.6 0.7 0.8 0.9 Fig Determination of CPZ in the EMETIL-25 tablet using the standard addition method (a) 0.07 mM (tab) (b) 0.08 mM (tab) ỵ mM (std) (c) 0.08 mM (tab) ỵ mM (std) (d) 0.08 mM (tab) ỵ mM (std) and (e) 0.08 mM (tab) ỵ mM (std) Concentration (M) 0.030 Concentration / μM 1.0 R = 0.9955 Table Results obtained from detection of CPZ in pharmaceutical tablets Current (μA) Technique a DPV 0.025 a 0.020 0.01 0.02 0.03 0.04 0.05 0.06 Concentration (μM) Fig (a) Differential pulse voltammogram of CPZ on peak current in 0.l M PBS (pH 7.0) at different concentrations (i) 0.01 mM (ii) 0.02 mM (iii) 0.03 mM (iv) 0.04 mM (v) 0.05 mM (vi) 0.06 mM (vii) 0.07 mM and (viii) 0.08 mM on PGE (b) Calibration plot of peak current versus concentration Table Reported experimental values of CPZ using different carbon based electrodes Electrode Analytical technique pH Linear range (mM LÀ1) LODa (mM LÀ1) Reference MGEb GPEd CPEf BDDEh GCEi PGEj CVc DPVe SWVg DPV DPV DPV 9.0 4.0 7.0 4.0 7.0 7.0 0.6e10.0 0.01e9.0 0.1e350 0.1e40 0.019e9.2 0.01e0.08 0.1 0.006 0.07 1.3 0.003 [33] [34] [24] [35] [1] Present work a c d e f g h i j Added (mM LÀ1) Found (mM LÀ1) Recovery (%) 0.07 0.08 0.07 ± 0.1 0.08 ± 0.1 99.99 100 Differential Pulse Voltammetry Acknowledgements (b) b Tablet sample Limit of detection Modified gold electrode Cyclic voltammetry Graphene paste electrode 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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 in Fig 3a As scan rate increased from 25