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ELECTROCHEMICAL DETERMINATION OF PARACETAMOL AT POLY(ORANGE DYE) MODIFIED CARBON PASTE ELECTRODE

BY USING CYCLIC VOLTAMMETRY

Chougoni Madhuri1, Sundupalle Kiranmai1, Duddukuru Saritha1, Vipparla Prabhakara Rao1, Gajulapalli Madhavi1, Heri Septya Kusuma2

ABSTRACT

A poly orange-G dye modified carbon paste electrode (MCPE) is prepared through electropolymerisation tech-nique by using cyclic voltammetry (CV). The electrochemical redox behavior of paracetamol (PA) on a poly(orange G)/CPE is investigated in PBS solution at pH of 7. The effect of pH, the scan rate and the concentration of PA is studied by using CV and DPV. It is a reversible process in which the anodic (oxidation) peak and the cathodic (re-duction) peak are recorded at a potential value of 0.3V. The poly(orange G)/CPE shows a better sensitivity towards PA. The LOD and LOQ of PA are found to be 1.81 nM and 6.05 nM with a linear dynamic range of 2.4 X 10-8 mol L-1 to 2.8 X 10-7 mol L-1. The proposed method is successfully applied for the quantification of PA in human urine and pharmaceutical samples with satisfactory results.

Keywords: paracetamol, poly orange G dye, electropolymerisation, cyclic voltammetry, differential pulse vol-tammetry.

Received 15 March 2018Accepted 01 February 2019

Journal of Chemical Technology and Metallurgy, 54, 4, 2019, 758-764

1 Electrochemical Research Laboratory, Department of Chemistry Sri Venkateswara University, Tirupati, India2 Department of Chemical Engineering, Faculty of Industrial Technology Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia E-mail: gmchem01@gmail.com; heriseptyakusuma@gmail.com

INTRODUCTION

The electropolymerisation technique is used for the development of conducting polymer modified elec-trodes. The unique and excellent optical, electrical, and mechanical properties of the conductive polymers [1 - 9] are useful for developing efficient and versatile sensing materials [10]. The electroactive polymer electrode is expected to have a uniform film thickness of good adher-ence to the electrode, a good stability, reproducibility, a great number of active sites, a large surface area, a high conductivity, well expressed catalytic activity [11 - 12]. Orange G (Gelb) is a synthetic azo dye. It is mainly included in staining formulations. But it can be used in modifying the properties of an electrode material through the development of a conducting polymer film.

Paracetamol (PA) is also known as acetoaminophen. It is the most commonly prescribed drug to treat fever by inhibiting the prostaglandins synthesis in the CNS. PA acts as an analgesic for the relief of mild to moderate

tooth, back, joint and postoperative pains [13 - 14]. PA is a weak acid of Pka of 9.5. It is absorbed and distributed in the body and is easily excreted through urine. It does not exhibit any side effects in therapeutic doses but due to hypersensitivity and over-dosage PA can lead to liver and kidney damage, skin diseases. The risk of damage is greater; it can be even fatal, in case of alcohol con-sumption [15 - 17].

In U.S., according to FDA, approximately 2000 causes of acute liver failures occur of which 60 % are due to PA over-dosage. Hence, it is necessary to develop an analytical method for the analysis of PA, which will be of a significance importance not only in clinical diagnosis, but also for a quality control of the pharmaceutical for-mulations. Many analytical techniques are used for the analysis of PA including liquid chromatography, HPLC, titrimetry, spectrophotometry, capillary electrophoresis [18 - 23]. They are time consuming and expensive. The electrochemical techniques are commonly used because of their low cost, high selectivity and simple operation.

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In this context, many nanomaterials modified electrodes [24 - 27] are developed for determination of PA.

The main purpose of this work is to develop a MCPE with poly orange G dye for the selective and sensitive determination of paracetamol. The poly (orange G)/CPE is also applied for the quantification of PA in human urine and pharmaceutical samples.

EXPERIMENTALReagents and solutions

All reagents used in this research were of an analyti-cal grade. The solutions were prepared with Millipore water. PA, NaH2PO4, Na2HPO4, a graphite powder, silicon oil and Orange G dye were supplied by HiMedia labo-ratories Pvt limited, Mumbai. PBS buffer was prepared by using 0.1M NaH2PO4 and 0.1M Na2HPO4 solutions prepared with Millipore water.

ApparatusThe electrochemical experiments were performed

using a model CHI610D CH-Instrument with a three electrode conventional cell. A bare CPE or a modi-fied CPE of a diameter of 3.0 mm acted as a working electrode, while a platinum wire was used as a counter electrode. The potential values were recorded against Ag/AgCl reference electrode. The pH values were ob-tained by using ELICO Li 120 pH meter.

Preparation of CPE and Poly (orange G)/CPEThe bare CPE was prepared by hand mixing of

graphite powder and silicon oil in a ratio of 70 % to 30 % in an agate motar. A homogeneous carbon paste was obtained. It was introduced to the cavity of a CPE of a diameter of 2 mm and the surface obtained was smooth-ened. The modified poly(orange G)/CPE was prepared by electropolymerisation of 1.0 mM of Orange G dye on the surface of CPE in PBS buffer of pH of 7. 15 voltam-metric cycles were applied in the potential range from -1.0 V to 1.5V at a scan rate of 50 mVs-1. After that the poly (orange G)/CPE was washed with Milli-Q water and left to dry at a room temperature.

RESULTS AND DISCUSSIONFig. 1 illustrates the electrochemical polymeriza-

tion process of poly orange dye on CPE. During this process an oxidation peak (O) and a reduction peak (R) are recorded at 933 mV and 748 mV, correspondingly. A

conductive polymer film is deposited on the surface of the carbon paste electrode. The reaction mechanism of the electropolymerization is presented in Scheme 1. The poly orange G dye undergoes deprotonation resulting in the formation of Poly orange G phenoxy radical. It participates in electrostatic interactions with the surface of the carbon paste electrode forming a uniform surface polymer film as evidenced by the schemmatic diagram reported in ref. [28].

Fig. 2 shows the cyclic voltammograms of PA at a concentration of 0.025 mM in PBS buffer solution of pH of 7 at a scan rate of 50 mVs-1. The dotted curve (a) refers to the bare CPE, while the solid curve (b) corre-

Fig. 1. Cyclic voltammograms for the electro polymeri-zation of 1.0 mM (orange G dye) on a CPE at the scan rate of 50 mVs-1 with 15 cycles.

Fig. 2. Cyclic voltammogram of bare CPE (dotted line) and a poly(orange G dye)/CPE using 0.025 mM PA in PBS at pH 7 with scan rate of 50 mVs-1.

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sponds to the poly(Orange G)/CPE. The MCPE shows a 3 fold increase of the anodic peak current (Ipa) and a 4 fold increase of the cathodic peak current(Ipc) when compared to those recorded on the bare CPE. The anodic peak potential (Epa) and the cathodic peak potential (Epc) refer to 394 mV and 314 mV, correspondingly. Both peaks separation in presence of PA is decreased when compared to that observed on the CPE. The poly(orange G)/CPE shows an excellent catalytic activity, a sensi-tivitivity and a good affinity for quantification of PA.

Fig. 3(a) presents the CV response of the electrocata-lytic redox reaction of PA in presence of poly(orange G)/CPE at different scan rates within the range of 50 mV s-1

- 500 mV s-1. Fig. 3(b) shows the calibaration plots of Ipa and Ipc versus the square root of the scan rate ( (1/ 2))u­ Linear relationships of R2 = 0.999 and R2 = 0.998, cor-respondingly, are obtained. This indicates clearly that an adsorption controlled process [29] is taking place. The electroactive surface area of the bare CPE is 0.06 cm2, while that of the poly (orange G)/CPE amounts to

0.12 cm2. The values of Epa values are plotted versus the logarithm of the scan rate (Fig. 3(c)) aiming to determine the kinetic parameters of the electrochemi-cal process. The values of α and ks are found equal to 0.6 and 3.49 s-1 with the application of the Laviron Equation [30]:

(1 ) (1 )

( ) (1 )

2.3

S

P

logK log logRTlog nF E

nFRT

a a a a

a au

= - + - -

- D-

where α is the electron transfer coefficient, Kss is the standard rate constant of the surface reaction, u is the scan rate, n is the number of the electrons transferred, F is the Faraday constant, while R is the universal gas constant. The n value is obtained from the intercept and the slope of the linear plot of Ep vs. lnu . It shows that equal number of protons (p) and electrons (e-) participate in the transfer examined.

Scheme 1. Electropolymerization of of poly(orange G dye).

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Fig. 3a. Cyclic voltammogram for poly(orange G dye)/CPE using 0.025mM PA in PBS at pH 7 with various scan rate of 50,100,150,200,250,300,350,400,450,500 mVs-1.

The effect of the buffer solution pH on the electro-chemical redox behavior of the poly (orange G dye)/CPE is studied. Fig. 4(a) presents the cyclic voltam-mograms obtained. It is evident that the anodic (Ipa) and cathodic (Ipc) peak currents in PA presence increase with pH increase from 5.5 to 7.0. The maximum peak current is observed at pH of 7.0. The peak currents are lower at pH of 7.5 but then increase at pH of 8.0. Fig. 4(b) shows the graphs of Ipa vs. pH and Epa vs. pH. The anodic peak in PA presence shifts in a negative direction with pH increase. The redox peak potential of PA shows linearity with pH ranging from 5.5 to 8.0 with a slope of 54 mV. The corresponding linear regression equation

Fig. 3b. The calibaration plots of both Ipa and Ipc Vs Square root of scan rates from 50-500 mV s-1.

Fig. 3c. The calibaration plots of both Epa and Epc Vs log V with scan rates from 50-500 mV s-1.

Fig. 4a. Cyclic voltammogram for poly(orange G dye)/CPE using 0.025 mM PA in PBS solution with pH value of 5.5 to 8.0 with scan rate of 50 mV s-1.

Fig. 4b. A plot of PA oxidation peak currents Vs PBS so-lution pH (5.5 - 8.0) and formal potential Vs pH (5.5 - 8) at scan rate 50 mV s-1.

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is presented by:2( ) 54 793 ( 0.9643)paE mV mV A Rm= + =

Paracetamol is an electroactive substance. The DPV technique is used for the determination of the detection limit (DL) of PA in case of using the poly (orange G)/CPE. Fig. 5 shows the anodic peak currents of PA. The anodic (oxidation) peak currents increase linearly with PA concentration increase. A linear dynamic range (LDR) from 2.4 X 10-8 mol L-1 to 2.8 X 10-7 mol L-1 is obtained. The corresponding regression equation is as follows:

2( ) 12.23 ( ) 11.2, 0.997paI A C M Rm m= + =

The limit of detection (LOD) and limit of quantification (LOQ) are obtained by using the formulae:

3

10

LODM

LOQM

s

s

=

=

where s is the standard deviation of blank, while M stands for the slope of the graph. The value of LOD is found equal to 1.81 nM, while that of LOQ amounts to 6.05 nM.

Real sample analysisThe poly (orange G)/CPE is used for the detection

of PA in human urine (collected from SVU Health Care Center, Tirupati). The 0.1 M urine sample is diluted to 100 ml with 0.1 M PBS of pH of 7.0 and used for an analysis without any pretreatment. Each time 24 ml of this solution are added to different volumes of PA solution of a known concentration. The solutions are analyzed by DPV technique.

500 mg tablet of PA pharmaceutical formulation is grinded to a fine powder by using a mortor.1 mg in 5 ml of D.H2O is further diluted to 25 ml. The solution obtained is investigated by DPV. The electrochemical response of the spiked standard solution of PA in case of using the poly (orange G)/CPE is recorded and the per-centage of recovery is calculated. The results obtained are listed in Table 2. The recoveries range from 93 % to 101 %. The results indicate that the poly (orange G)/CPE has a high sensitivity in respect to the analysis of PA in human urine and pharmaceutical samples.

Fig. 5. DPV obtained for poly(orange)/CPE due to the addition of PA concentration at pH 7.0 of PBS buffer solution.Inset shows the calibaration plot of oxidation peak current Vs concentration of PA.

Table 1. The comparison of the performance of poly(orange G)/CPE with other modified electrode sensors for the determination of PA. Electrode Technique Linear range(µM) Detection

Limit(µM) Reference

rGO-PEDOT NT/GCE

DPV 1-35 0.4 31

MCPE/PR DPV 0.7-100 0.53 32 GO/NiO NP DPV 0.1 -2.9 0.067 33 CovalentLBL CMWCNTS/GCE

DPV 1-200 0.092 34

Poly(orange G)/CPE

DPV 0.02-28 0.018 (Present Work)

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CONCLUSIONS

The poly (orange G)/CPE shows an excellent elec-trocatalytical behavior towards the oxidation of paraceta-mol. This fabricated sensor exhibits a good stability, sensitivity and selectivity in respect to paracetamol quantification. The lowest detection limit refers to 1.8 nM .The sensor is practically applied for the analysis of PA in human urine and pharmaceutical samples. The recoveries are in an acceptable range.

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Human Urine

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Paracetamol (Tablet) 500 mg

0.1 0.095 95 0.2 0.198 99 0.3 0.298 101

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