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Poly (glycine) modified carbon paste electrode for simultaneous determination of catechol and hydroquinone: A voltammetric study
Journal of Electroanalytical Chemistry 823 (2018) 730–736
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Poly (glycine) modified carbon paste electrode for simultaneous determination of catechol and hydroquinone: A voltammetric study
T
⁎
K.V. Harishaa, B.E. Kumara Swamya, , Eno E. Ebensob,c a
Department of PG Studies and Research in Industrial Chemistry, Kuvempu University, Jnana Sahyadri, Shankaraghatta, 577451 Shimoga, Karnataka, India Department of Chemistry, School of Mathematics and Physical Sciences, Faculty of Agriculture, Science and Technology, North-West University (Mafikeng Campus), Private Bag X2046, Mmabatho 2735, South Africa c Material Science Innovation and Modelling (MaSIM) Research Focus Area, Faculty of Natural and Agricultural Sciences, North-West University (Mafikeng Campus) Private Bag X2046, Mmabatho 2735, South Africa b
A R T I C LE I N FO
A B S T R A C T
Keywords: Electropolymerisation Catechol Hydroquinone Glycine Cyclic voltammetry
The poly (glycine) modified carbon paste electrode (MCPE) was fabricated for the determination of catechol and hydroquinone by cyclic voltammetric and differential pulse voltammetric techniques. The poly (glycine) MCPE exhibits high sensitivity and selectivity in the determination of catechol and hydroquinone in a binary mixture. The effect of scan rate was examined and it was found to be adsorption-controlled. The effect of concentration was studied in the range of 20-180 μM. The limit of detection (3S/M) and limit of quantification (10S/M) for CC were found to be 0.16 μM and 0.55 μM, respectively and for HQ the values were 0.20 μM and 0.66 μM, respectively. In order to show the selectivity of the electrode interference study was performed by varying the concentration of one analyte while keeping another analyte constant. Overall, a simple experimental procedure for fabricating the poly (glycine) MCPE was proposed with the merits of sensitivity, selectivity, reproducibility, and anti-fouling property towards the electroactive species and also in biological matrices.
1. Introduction Phenolic compounds and its derivatives are important but toxic starting materials in a broad range of chemical manufacturing processes. Especially in coal conversion industry, phenolic residues are considered as an acute environmental problem [1]. Catechol (CC) (also known as pyrocatechol or 1,2-dihydroxy benzene) is an simple organic moiety, first discovered by destructive distillation of the plant extract catechin [2]. Small amounts of catechol occur naturally in fruits and vegetables. Upon mixing the enzyme with the substrate and exposure to oxygen (as when a potato or apple is cut and left out), the colorless catechol oxidizes to reddish-brown melanoid pigments, derivatives of benzoquinone. Benzoquinone is said to be antimicrobial, which slows the spoilage of wounded fruits and other plant parts. Catechol is produced by the reversible two-electron, two-proton reduction of 1,2benzoquinone [3,4]. Hydroquinone (HQ) (1,4-dihydroxy benzene) is another phenolic compound coexisting with catechol in environmental samples. As an environmental pollutant it is toxic and can result in cancer like acute myeloid leukaemia [5]. High concentrations of HQ can incur headache, fatigue, tachycardia, decompensation, the damage to kidney, and even death. Long-term respiration in the atmosphere
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containing low concentrations of HQ can incur cough, anorexia, nausea, spew, and pigmentation of the eye. Even low concentrations of CC in foods and cigarette smokes may cause mutagenesis and cancerous alteration [6–8]. These two isomers are widely used in industrial products such as cosmetics, pesticides, flavouring agents. Very poor biological degradation in environment makes catechol and hydroquinone is harmful to humans, even in a minute concentration are the major causes for environmental pollution [9]. These two isomers are included as environmental pollutants in the lists of Environmental Protection Agency (EPA) and the European Union (EU) [10]. Several analytical methods have been reported for the simultaneous determination of these isomers such as spectrophotometry [11], chemiluminescence [12], HPLC [13]. However, these methods are generally expensive and time consuming. Because of the same phenolic moieties, overlapping of the peaks at same oxidation potential, co-existence and their competitive adsorption at the electrode surface makes the relationship between the voltammetric response of CC and HQ and their concentration in the mixtures nonlinear [14]. Therefore, it is important to establish a simple and fast analytical method for sensitive and selective determination of HQ and CC in different matrices. To overcome these limitations, electrochemical methods such as
Corresponding author. E-mail address: [email protected] (B.E. Kumara Swamy).
https://doi.org/10.1016/j.jelechem.2018.07.021 Received 27 November 2017; Received in revised form 11 July 2018; Accepted 13 July 2018 1572-6657/ © 2018 Elsevier B.V. All rights reserved.
Journal of Electroanalytical Chemistry 823 (2018) 730–736
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voltammetric one's were extensively used because of their simplicity in the experimental procedure, rapid and quick response, excellent reproducibility, good stability, low cost and low detection limit [15–17]. In the present scenario carbon paste electrodes became one of the most commonly used electrodes due to its simple preparation, low cost, easy renewability, good sensitivity, low background current and fast response [18,19]. However, the absence of conducting binder in the CPE will lower the sensitivity of the detection system. Many chemically modified electrodes were prepared for the simple and simultaneous determination of isomers such as poly (crystal violet) graphene modified carbon ionic liquid electrode [20], poly (brilliant blue) modified carbon paste electrode [21], poly (glutamic acid) glassy carbon electrode [22], poly(glycine) modified glassy carbon electrode [23].However, polymer modified electrodes (PMEs) have received great attention in recent years, as the polymer film which is deposited onto the surface of the electrode by electropolymerisation has good stability, reproducibility, more active reaction sites, homogeneity, and strong adherence to the electrode surface [24,25]. The present work describes an electropolymerisation of an amino acid say glycine on the surface of carbon paste electrode by cyclic voltammetry. The fabricated electrode has the capacity to resolve the voltammetric peaks of catechol and hydroquinone in a binary mixture. A simple method was reported for the determination of dihydroxy benzene isomers.
Fig. 1. Cyclic voltammograms of preparation of poly (glycine) modified CPE.1 mM aqueous solution of glycine was taken in 0.2 M PBS of pH 7.0 at 5 cycles with scan rate 0.1 V s−1.
voltammograms. After the few cycles there is no increment in the peak height and it becomes more stable; which suggests polymerisation growth reached the saturation level [8,19,21]. The extent of thickness of the polymer film has a significant influence on the electrocatalytic activity of the modified electrode. It is well known that, as the thickness of the modifier layer increases the electron transfer rate decreases due to insufficient exposure of reactive sites on the electrode. The thickness can be controlled by varying the cyclic voltammetry parameters. Therefore 5 repetitive cycles were fixed as an optimum for the fabrication of poly(glycine) modified CPE. The probable electropolymerisation mechanism of glycine is described in Scheme 1.
2. Experimental section 2.1. Apparatus and reagents Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were performed in an analytical system model CHI-660c potentiostat (Electrochemical workstation, USA). The conventional three electrode electrochemical cell contained a saturated calomel electrode (SCE) as a reference, platinum wire as a counter electrode and the working electrode was either bare CPE or poly(glycine) modified CPE. The pH values were measured with a digital pH meter MK VI (systronics). All the obtained oxidation potential values are given versus SCE. Catechol (CC), hydroquinone (HQ) and glycine were purchased from Himedia. A stock solution of CC (25 × 10−4M), HQ (25 × 10−4M) and Glycine (25 × 10−3M) were prepared in double demineralized water. Graphite powder (50 μm particle size) was purchased from Loba and silicon oil (as binder) was purchased from Himedia. All chemicals were of analytical grade. The chemicals for the preparation of buffer solution were purchased from Merck. The 0.2 M phosphate buffer solution (PBS) was prepared by mixing standard stock solutions of 0.2 M NaH2PO4·H2O and 0.2 M Na2HPO4. All the solutions were freshly prepared prior to analysis. All the other solutions were prepared using double distilled water.
3.2. Electrochemical characterization of poly (glycine) modified CPE In order to evaluate the performance of the poly (glycine) modified CPE, potassium ferrocyanide[K4Fe(CN)6] was selected as an electrochemical probe. Fig. 2 shows electrochemical response of 1.0 mM [K4Fe (CN)6] at bare CPE (dashed line) and poly(glycine) modified CPE (solid line) in 1 M KCl at the scan rate 0.1Vs−1. A pair of redox peaks was observed for BCPE and with the modified CPE. The poly (glycine) MCPE shows lower peak potential difference (ΔEp), it was found to be 0.093 V and 0.101 V for bare and MCPE, respectively. As ΔEp is a function of electron transfer rate, lower the ΔEp means higher electron transfer rate. The result shows a dramatic change in the peak current at
2.2. Preparation of working electrodes The bare carbon paste electrode was prepared according to literature [19]. Electropolymerisation of glycine on the surface of carbon paste electrode was carried out by placing 1.0 mM glycine solution along with 0.2 M PBS of pH 7.0 in an electrochemical cell. The potential sweeping was maintained between −0.5 and +1.8 V at 0.1 V s−1 for 5 multiple cycles. Later the electrode was rinsed and washed with double distilled water prior to measurement. 3. Results and discussions 3.1. Optimisation condition for working electrode The modification procedure for the preparation of working electrode was mentioned in the Section 3.2. From the Fig. 1, it can be seen that, the anodic peak current enhances gradually in the repetitive cyclic
Scheme 1. Probable electropolymerisation mechanism of glycine. 731
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The heterogeneous rate constant (k0) values was determined from the experimental peak potential difference (ΔEp) data's, Eq. (2) was used for such voltammograms whose ΔEp values are greater than 10 mV [15,21].
ΔEp = 201.39 log (υ/k0) − 301.78
(2)
From the experimental ΔEp values as shown in the Table 1 and Eq. (2); the values of the k0 for the CC and HQ oxidation was determined for poly (glycine) modified CPE; the corresponding parameters are tabulated in Table 1. 3.4. The effect of concentration of catechol on poly (glycine) modified CPE The effect of concentration of CC was studied at poly (glycine) modified CPE in 0.2 M PBS pH 7.0 at the scan rate of 50 mV s−1. From the Fig. 5A it is clear that the peak potential of CC shift towards positive side with increasing the concentration of catechol in the range 0.2 × 10−4–2.0 × 10−4 M. The plot of Ipa versus concentration of CC shows linear relationship with regression equation of Ipa (10−5A) = 2.69(Co, 10−5 M/L) + 3.9(r2 = 0.9963) as in Fig. 5B. The limit of detection (LOD) and the limit of quantification (LOQ) were calculated by using the Eqs. (3) and (4) [21]. The values of LOD and LOQ were 0.16 μM and 0.55 μM, respectively. Therefore, the proposed method shows good results with improved detection limit than the results as reported in Table 2 [27–30], S is the standard deviation and M is the slope of calibration plot.
Fig. 2. Cyclic voltammograms of 1 mM potassium ferrocyanide at bare CPE (dashed line) and poly (glycine) MCPE (solid line) at scan rate of 0.05 V s−1 in 1 M KCl.
fabricated electrode [16,26].
3.3. Electrochemical investigation of catechol at the poly (glycine) modified CPE Fig. 3 shows the cyclic voltammograms obtained for 0.1 mM CC in 0.2 M PBS of pH 7.0 at poly(glycine) modified CPE (solid line) and bare CPE (dashed line) recorded at the scan rate of 50 mV s−1. At the bare CPE CC shows redox peaks with poor response and oxidation takes place at 0.215 V. On the other hand, at poly (glycine) modified CPE a significant enhancement in the current signals was observed and oxidation peak was located at 0.183 V. Therefore, the result suggests poly (glycine) modified CPE catalyses the oxidation process of CC. The oxidation mechanism of CC and HQ is shown in Scheme 2. The effect of applied scan rate for the oxidation of 0.1 mM CC in 0.2 M PBS of pH 7.0 was investigated with different scan rates in the range from 0.01–0.20 V s−1 at poly(glycine) modified CPE. The poly (glycine) modified CPE showed increase in the current signals with increasing scan rate as shown in Fig. 4A. The graph of anodic peak current (Ipa) versus scan rate (υ) was plotted (inset Fig. 4B), the result shows good linearity with correlation coefficient of r2 = 0.9981. Therefore, the results indicate that the electrochemical reaction of catechol at poly (glycine) modified CPE was adsorption-controlled [19].
LOD = 3S/M
(3)
LOQ = 10S/M
(4)
3.5. Electrocatalytic oxidation of hydroquinone at the poly (glycine) MCPE Fig. 6 shows the cyclic voltammograms obtained for the anodic oxidation of 0.1 mM HQ in 0.2 M PBS of pH 7.4 at bare CPE (dashed line) and poly (glycine) modified CPE (solid line) with the scan rate 50 mV s−1. At the bare CPE hydroquinone low redox current response and a broad voltammogram was obtained, the oxidation takes place at 0.075 V. On the other hand, the poly(glycine) modified CPE shows significant increase in the current signals yielding a sharp and sensitive voltammogram, the oxidation potential was observed at 0.0519 V. This minimization of over potential and refinement in the current response suggests the catalytic capability of fabricated electrode. The effect of scan rates on the oxidation of 0.1 mM HQ in 0.2 M PBS of pH 7.0 was investigated in the range 0.01–0.20 V s−1. The poly (glycine) modified CPE showed increase in the current signals with increasing scan rate according to Randles-Sevick's equation as shown in Fig. 7A. In order to confirm the electrode process, the graph of Ipa versus υ (inset Fig. 7B) was plotted and the result so obtained is in good linearity with correlation coefficient, r2 = 0.9965. The value suggesting that electrode process was controlled by adsorption. The effect of concentration of HQ was studied at poly (glycine) modified CPE in 0.2 M PBS pH 7.0 at the scan rate of 50 mV s−1. From Fig. 8A it is clear that the anodic peak current of hydroquinone was increased due to increasing in the concentration of HQ, the peak potential was shifted towards more positive side in the range 0.2 × 10−4–2.0 × 10−4 M. The plot of Ipa versus concentration of HQ (Fig. 8B) follows linear regression equation of Ipa (10−5A) = 1.8 (Co, 10−5 M/L) + 4.9 (r2 = 0.9946). The LOD and LOQ were found to be 0.20 μM and 0.66 μM, respectively. 3.6. Simultaneous determination of CC in presence of HQ at poly (glycine) modified CPE
Fig. 3. Cyclic voltammograms of 0.1 mM CC in 0.2 M PBS solution of pH 7.0 at bare CPE(dashed line) and poly (glycine) modified CPE (solid line) at scan rate of 0.05 V s−1.
It is quite difficult to determine electroactive species like CC and HQ simultaneously when they are present in a binary mixture. Because of 732
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Scheme 2. Mechanism of oxidation of catechol and hydroquinone. Table 1 Variation of the voltammetric parameters gathered from the plots shown in Fig. 4 and Fig. 7 as a function of the scan rate. υ inV/s
0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.12 0.14 0.16 0.18 0.20
Fig. 4. (A) Cyclic voltammograms of 0.1 mM CC in 0.2 M PBS solution of pH 7.4 at poly (glycine) modified CPE with different scan rate (a–o: 0.01 V s−1 to 0.20 V s−1) (B) Graph of anodic peak current versus scan rate(C) Graph of anodic peak current versus square root of scan rate.
ΔEp (V)
k0(mV/s)
Catechol (cc)
Hydroquinone (HQ)
Catechol (cc)
Hydroquinone (HQ)
0.04 0.06 0.07 0.08 0.09 0.01 0.12 0.13 0.15 0.15 0.17 0.20 0.21 0.22 0.23
0.05 0.06 0.07 0.09 0.10 0.12 0.13 0.15 0.16 0.17 0.19 0.22 0.23 0.26 0.27
31.5 88.8 159.7 251.9 350.9 462.6 583.1 712.6 850.1 996.5 1309.5 1651.4 2018.1 2407.5 2822.8
31.5 88.8 159.7 251.9 351.0 462.8 583.3 712.9 850.3 996.9 1310.2 1652.3 2019.4 2410.3 2825.7
obtained from the linearity were 55 mV/pH and 52 mV/pH for CC and HQ respectively. The results suggest that an equal number of protons and electrons are involved in the oxidation process [19]. This was consistent with the reported literature [21,31].
the same phenolic structure and similar oxidation potentials the discrimination in the voltammetric signal was not observed at bare CPE. Fig. 9 shows the cyclic voltammograms of simultaneous determination of 1 × 10−4 M CC, 1 × 10−4 M HQ in 0.2 M PBS of pH 7.0. The cyclic voltammogram obtained for the mixture of CC and HQ at bare CPE (dashed line) was not clearly defined and shows overlapped oxidation potential at 0.215 V. On the other side, the poly (glycine) modified CPE (solid line) shows well-defined oxidation peaks for CC and HQ located at 0.191 V and 0.0816 V, respectively and peak to peak separation is 0.109 V. This indicates that modified CPE act as a good electrochemical sensor for the simultaneous determination of poly (glycine) CC and HQ present in the binary mixture. The influence of PBS pH on the simultaneous determination of CC and HQ in a binary mixture was evaluated at poly(glycine) modified CPE by using cyclic voltammetric technique. Generally the oxidation was pH dependent and the oxidation peak potentials shifts towards more negative potential with increasing pH in the range 5.5 to 8.0 as shown in the Fig. 10A. The graph of Epa versus pH indicates the linear dependence of each other as in the inset Fig. 10B and C. The slopes
3.7. Interference study Differential pulse voltammograms were recorded due its higher current sensitivity and absence of non-faradic current. The determination of CC and HQ at poly (glycine) modified CPE in 0.2 M PBS of pH 7.0 was conducted as shown in the Fig. 11. At bare CPE overlapped peak was observed at 0.116 V. As poly (glycine) modified CPE resolved oxidation peaks into well-defined peaks located at 0.125 V for CC and 0.015 V for HQ, respectively. The peak to peak separation was 0.110 V. This result was more than enough for the determination of individual components. The analytical performance of the modified electrode can be evaluated by its capability of determining the species individually in the presence of interferents. It can be carried out by varying concentration of one species, while the other kept constant. From the Fig. 12A and B, 733
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Fig. 5. (A) Cyclic voltammograms of CC in 0.2 M PBS solution of pH 7.0 at poly (glycine) modified CPE with different concentration (a–j: 0.2 × 10−4 to 2.0 × 10−4 M) (B) Graph of anodic peak current versus concentration of CC.
Fig. 7. (A) Cyclic voltammograms of 0.1 mM HQ in 0.2 M PBS solution of pH 7.4 at poly (glycine) modified CPE with different scan rate (a–o: 0.01 V s−1 to 0.20 V s−1) (B) Graph of peak current versus scan rate (C) Graph of peak current versus square root of scan rate.
Table 2 Comparison of limit of detection with different modified electrodes and poly (glycine) modified CPE. Modified Electrodes
LDHf/GCE LRG/GCE Poly(Phenylalanine) MWNT/GCE MWCNT–NF–PMG/GCE Silsesquioxane/MCPE [Cu(Sal-β-Ala)(3,5-DMPz)2]/ MWCNTs/GCE Influence of micelles/GCE CNx/GCE Poly(calmagite) MCPE RGO–MWNTs Poly(glycine) modified CPE
Limit of detection (μM)
Method
References
CC
HQ
1.2 0.8 0.7 0.2 31.0 10 3.5
9.0 0.5 1.0 0.75 18.1 10 1.46
DPV DPV DPV DPV CV DPV DPV
[27] [28] [29] [30] [32] [33] [34]
3.0 2.71 2.55 1.8 0.16
8.0 1.20 1.70 2.6 0.20
DPV LSV CV DPV CV
[35] [36] [37] [38] This work
Fig. 8. (A) Cyclic voltammograms of HQ in 0.2 M PBS solution of pH 7.0 at poly (glycine) modified CPE at the scan rate of 0.05 V s−1 with different concentration (a–j: 0.2 × 10−4 to 2.0 × 10−4 M) (B) Graph of anodic peak current versus concentration of HQ.
Fig. 6. Cyclic voltammograms of 0.1 mM HQ in 0.2 M PBS solution of pH 7.0 at bare CPE (dashed line) and poly(glycine) modified CPE (solid line) at scan rate of 0.05 V s−1. Fig. 9. Cyclic voltammograms for simultaneous determination of 0.1 mM CC and 0.1 mM HQ at bare CPE (dashed line) and poly(glycine) modified CPE (solid line) at scan rate of 0.05 V s−1.
it can be seen that increase in the anodic peak current was linearly varied with CC concentration from 0.2–1.4 × 10−4 M, while keeping the concentration of hydroquinone 0.2 × 10−4 M constant. Similarly, 734
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Fig. 10. (A) Cyclic voltammograms of the poly (glycine) MCPE in 0.2 M PBS solution containing 0.1 mM CC and 0.1 mM HQ with different pH (a–f: 5.5 to 8.0) at scan rate of 0.05 V s−1 (B) The effect of pH on the peak potential response of 0.1 mM CC in 0.2 M PBS solution of pH 7.4 (C) The effect of pH on the peak potential response of 0.1 mM HQ in 0.2 M PBS solution of pH 7.0.
Fig. 13. (A) Differential pulse voltammograms of (a-g: 0.2 × 10−4 to 1.4 × 10−4 M) HQ in 0.2 M PBS of pH 7.4 in presence of 0.2 × 10−4 M CC at poly (glycine) MCPE (B) Graph of anodic peak current versus concentration of HQ.
by varying the HQ concentration from 0.2–1.4 × 10−4 M and keeping the concentration of CC 0.2 × 10−4 M constant, only the peak current of HQ was increased as shown in Fig. 13A and Fig. 13B. The results suggest that oxidation of both of the species occurs independently and the problem of interference was effectively resolved at the modified electrode. 4. Conclusion In the present study electropolymerisation of glycine was carried out on the surface of bare CPE and its application for the electrochemical determination of CC and HQ was investigated. The result shows that the poly (glycine) modified CPE not only exhibited strong electrocatalytic activity towards the oxidation of CC and HQ with the detection limit of 0.16 μM and 0.20 μM respectively, and but also resolved the overlapping peaks of CC and HQ into two well-defined peaks by cyclic voltammetric and differential pulse voltammetric techniques. Because of its electrocatalytic capability, selectivity, sensitivity and reproducibility the poly(glycine) modified CPE was very useful in the development of sensors for the simultaneous determination of catechol and hydroquinone in the field of electro-analytical chemistry.
Fig. 11. Differential pulse voltammogram obtained for 0.1 mM CC and 0.1 mM HQ in 0.2 M PBS solution of pH 7.4 at bare CPE (A) and poly (glycine) modified CPE.
References [1] H. Kotte, B. Gruendig, K.D. Vorlop, B. Strehlitz, U. Stottmeister, Methyl phenazonium-modified enzyme sensor based on polymer thick films for sub nanomolar detection of phenols, Anal. Chem. 6 (1995) 65–70. [2] Y.G. Sun, H. Cui, Y.H. Li, X.Q. Lin, Determination of some catechol derivatives by a flow injection electrochemiluminescent inhibition method, Talanta 53 (2000) 661–666. [3] H. Du, J. Ye, J. Zhang, X. Huang, C. Yu, A voltammetric sensor based on graphenemodified electrode for simultaneous determination of catechol and hydroquinone, J. Electroanal. Chem. 650 (2011) 209–213. [4] H.S. Han, J.M. You, H. Seol, H. Jeong, S. Jeon, Electrochemical sensor for hydroquinone and catechol based on electrochemically reduced GO-terthiophene-CNT, Sensors Actuators B 194 (2014) 460–469. [5] M. Gaskell, K.I.E.M. Luckie, P.B. Farmer, Comparison of the mutagenic activity of the benzene metabolites, hydroquinone and para-benzoquinone in the supF forward mutation assay: a role for minor DNA adducts formed from hydroquinone in benzene mutagenicity, Mutat. Res. 554 (2004) 387–398. [6] G.H. Zhao, M.F. Li, Z.H. Hu, H.X. Li, T.C. Cao, Electrocatalytic redox of hydroquinone by two forms of L-proline, J. Mol. Catal. B 255 (2006) 86–91. [7] M.A. Aziz, T. Selvaraju, H. Yang, Selective determination of catechol in the presence of hydroquinone at bare indium tin oxide electrodes via peak-potential separation and redox cycling by hydrazin, Electroanalysis 19 (2007) 1543–1546. [8] Y. Zhou, W. Tang, F. Dang, S. Chai, L. Zhang, Electrochemical characterization of poly-beryllon II modified carbon paste electrode and its application to selective determination of pyrocatechol and hydroquinone, Colloids Surf. B: Biointerfaces 118 (2014) 148–153.
Fig. 12. (A) Differential pulse voltammograms of (a-g: 0.2 × 10−4 to 1.4 × 10−4 M) CC in 0.2 M PBS of pH 7.4 in presence of 0.2 × 10−4 M HQ at poly (glycine) MCPE (B) Graph of anodic peak current versus concentration of CC.
735
Journal of Electroanalytical Chemistry 823 (2018) 730–736
K.V. Harisha et al.
[9] Rekha, B.E.K. Swamy, P.S. Ganesh, Poly(alcianblue) modified carbon paste electrode for the determination of catechol in presence hydroquinone: a voltammetric study, Biosens. Bioelectron. 7 (2016) 217. [10] A.J.S. Ahammad, S. Sarker, M.A. Rahman, J.J. Lee, Simultaneous determination of hydroquinone and catechol at an activated glassy carbon electrode, Electroanalysis 22 (2010) 694–700. [11] A. Afkhami, H.A. Khatami, Indirect kinetic-spectrophotometric determination of resorcinol, catechol, and hydroquinone, J. Anal. Chem. 56 (2001) 429–432. [12] L.J. Zhao, B. Lv, H. Yuan, Z. Zhou, D. Xiao, A sensitive chemiluminescence method for determination of hydroquinone and catechol, Sensors 7 (2007) 578–588. [13] G. Marrubini, E. Calleri, T. Coccini, A.F. Castoldi, L. Manzo, Direct analysis of phenol, catechol and hydroquinone in human urine by coupled-column HPLC with fluorimetric detection, Chromatographia 62 (2005) 25–31. [14] P. Yang, Q. Zhu, Y. Chen, F. Wang, Simultaneous determination of hydroquinone and catechol using poly(p-aminobenzoic acid) modified glassy carbon electrode, J. Appl. Polym. Sci. 113 (2009) 2881–2886. [15] S.C. Avendano, G.A. Angles, M.T.R. Silva, G.R. Pina, M.R. Romo, M.P. Pardave, On the electrochemistry of dopamine in aqueous solution. Part I: the role of [SDS] on the voltammetric behavior of dopamine on a carbon paste electrode, J. Electroanal. Chem. 609 (2007) 17–26. [16] K.V. Harisha, B.E.K. Swamy, H. Jayadevappa, P.S. Ganesh, Electrochemical sensor for the determination of adrenaline in presence of acetaminophen at poly (alanine) modified carbon paste electrode: a cyclic voltammetric study, Biosens. Bioelectron. 7 (2016) 230. [17] P.S. Ganesh, B.E.K. Swamy, Cyclic voltammetric determination of catechol and hydroquinone at TX-100 modified carbon paste electrode, Anal. Bioanal. Chem. 8 (5) (2016) 615–628. [18] H.N.A. Mustafa, I.M. Isa, N.M. Ali, N. Hashim, M. Musa, S.A. Ghani, Amperometric detection of hydroquinone at modified ionic liquid graphene composite paste electrode, Int. J. Electrochem. Sci. 10 (2015) 9232–9245. [19] K.V. Harisha, B.E.K. Swamy, H. Jayadevappa, C.C. Vishwanath, Voltammetric determination of folic acid in presence of dopamine and ascorbic acid at poly(alanine) modified carbon paste electrode, Anal. Bioanal. Chem. 7 (2015) 454–465. [20] W. Sun, Y. Wang, Y. Lu, A. Hu, F. Shi, Z. Sun, High sensitive simultaneously electrochemical detection of hydroquinone and catechol with a poly(crystal violet) functionalized graphene modified carbon ionic liquid electrode, Sensors Actuators B Chem. 188 (2013) 564–570. [21] P.S. Ganesh, B.E.K. Swamy, Simultaneous electroanalysis of hydroquinone and catechol at poly(brilliant blue) modified carbon paste electrode, J. Electroanal. Chem. 756( (2015) 193–200. [22] L. Wang, P. Huang, J. Bai, H. Wang, L. Zhang, Y. Zhao, Direct simultaneous electrochemical determination of hydroquinone and catechol at a poly(glutamic acid) modified glassy carbon electrode, Int. J. Electrochem. Sci. 2 (2007) 123–132. [23] L. Wang, P. Huang, H. Wang, J. Bai, L. Zhang, Y. Zhao, Electrocatalytic response of hydroquinone and catechol at polyglycine modified glassy carbon electrode, Int. J. Electrochem. Sci. 2 (2007) 216–225. [24] R.F. Rane, C.D. Blaha, Detection of catecholamines in brain tissue:surface-modified
[25] [26]
[27]
[28]
[29]
[30]
[31]
[32]
[33]
[34]
[35]
[36]
[37]
[38]
736
electrodes enabling in vivo investigations of dopamine function, Langmuir 6 (1990) 56–65. A.G. Ewing, M.A. Dayton, R.M. Wightman, Pulse voltammetry with microvoltammetric electrodes, Anal. Chem. 53 (1981) 1842–1847. O. Gilbert, B.E.K. Swamy, U. Chandra, B.S. Sherigara, Simultaneous detection of dopamine and ascorbic acid using polyglycine modified carbon paste electrode: a cyclic voltammetric study, J. Electroanal. Chem. 636 (2009) 80–85. M. Li, F. Ni, Y. Wang, S. Xu, D. Zhang, S. Chen, L. Wang, Sensitive and facile determination of catechol and hydroquinone simultaneously under co-existence of resorcinol with a Zn/Al layered double hydroxide film modified glassy carbon electrode, Electroanalysis 21 (13) (2009) 1521–1526. T. Lai, W. Cai, W. Dai, J. Ye, Easy processing laser reduced graphene: a green and fast sensingplatform for hydroquinone and catechol simultaneous determination, Electrochim. Acta 138 (2014) 48–55. L. Wang, P. Huang, J. Bai, H. Wang, L. Zhang, Y. Zhao, Simultaneous electrochemical determination of phenol isomers in binary mixtures at a poly(phenylalanine) modified glassy carbon paste electrode, Int. J. Electrochem. Sci. 1 (2006) 403–413. H.Q.C. Zhang, Simultaneous determination of hydroquinone and catechol at glassy carbon electrode modified with multi-wall carbon nanotubes, Electroanalysis 17 (10) (2005) 832–838. P.S. Ganesh, B.E.K. Swamy, Simultaneous electroanalysis of norepinephrine, ascorbic acid and uric acid using poly(glutamic acid) modified carbon paste electrode, J. Electroanal. Chem. 752 (2015) 17–24. Y. Umasankar, A.P. Periasamy, S.M. Chen, Electrocatalysis and simultaneous determination of catechol and quinol by poly(malachite green) coated multi-walled carbon nanotube film, Anal. Biochem. 411 (2011) 71–79. P.S.D. Silva, B.C. Gasparini, H.A. Magosso, A. Spinelli, Electrochemical behaviour of hydroquinone and catechol at a silsesquioxane-modified carbon paste electrode, J. Braz. Chem. Soc. 24 (4) (2013) 695–699. L.A. Alshahrani, X. Li, H. Luo, L. Yang, M. Wang, S. Yan, P. Liu, Y. Yang, Q. Li, The simultaneous electrochemical detection of catechol and hydroquinone with [Cu (Sal-β-Ala)(3,5-DMPz)2]/SWCNTs/GCE, Sensors 14 (2014) 22274–22284. J. Peng, Z.N. Gao, Influence of micelles on the electrochemical behaviours of catechol and hydroquinone and their simultaneous determination, Anal. Bioanal. Chem. 384 (2006) 1525–1532. J. Dong, X. Qu, L. Wang, C. Zhao, J. Xu, Electrochemistry of nitrogen-doped carbon nanotubes (CNx) with different nitrogen content and its application in simultaneous determination of dihydroxybenzene isomers, Electroanalysis 20 (18) (2008) 1981–1986. P.S. Ganesh, B.E.K. Swamy, Rekha, Electroanalysis of catechol in presence of hydroquinone at poly(calmagite) modified carbon paste electrode: a voltammetric study, Sci. Lett. 5 (2016) 236. F. Hu, S. Chen, C. Wang, R. Yuan, D. Yuan, C. Wang, Study on the application of reduced graphene oxide and multiwall carbon nanotubes hybrid materials for simultaneous determination of catechol, hydroquinone, p-cresol and nitrite, Anal. Chim. Acta 724 (2012) 40–46.
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Journal of Electroanalytical Chemistry journal homepage: www.elsevier.com/locate/jelechem
Poly (glycine) modified carbon paste electrode for simultaneous determination of catechol and hydroquinone: A voltammetric study
T
⁎
K.V. Harishaa, B.E. Kumara Swamya, , Eno E. Ebensob,c a
Department of PG Studies and Research in Industrial Chemistry, Kuvempu University, Jnana Sahyadri, Shankaraghatta, 577451 Shimoga, Karnataka, India Department of Chemistry, School of Mathematics and Physical Sciences, Faculty of Agriculture, Science and Technology, North-West University (Mafikeng Campus), Private Bag X2046, Mmabatho 2735, South Africa c Material Science Innovation and Modelling (MaSIM) Research Focus Area, Faculty of Natural and Agricultural Sciences, North-West University (Mafikeng Campus) Private Bag X2046, Mmabatho 2735, South Africa b
A R T I C LE I N FO
A B S T R A C T
Keywords: Electropolymerisation Catechol Hydroquinone Glycine Cyclic voltammetry
The poly (glycine) modified carbon paste electrode (MCPE) was fabricated for the determination of catechol and hydroquinone by cyclic voltammetric and differential pulse voltammetric techniques. The poly (glycine) MCPE exhibits high sensitivity and selectivity in the determination of catechol and hydroquinone in a binary mixture. The effect of scan rate was examined and it was found to be adsorption-controlled. The effect of concentration was studied in the range of 20-180 μM. The limit of detection (3S/M) and limit of quantification (10S/M) for CC were found to be 0.16 μM and 0.55 μM, respectively and for HQ the values were 0.20 μM and 0.66 μM, respectively. In order to show the selectivity of the electrode interference study was performed by varying the concentration of one analyte while keeping another analyte constant. Overall, a simple experimental procedure for fabricating the poly (glycine) MCPE was proposed with the merits of sensitivity, selectivity, reproducibility, and anti-fouling property towards the electroactive species and also in biological matrices.
1. Introduction Phenolic compounds and its derivatives are important but toxic starting materials in a broad range of chemical manufacturing processes. Especially in coal conversion industry, phenolic residues are considered as an acute environmental problem [1]. Catechol (CC) (also known as pyrocatechol or 1,2-dihydroxy benzene) is an simple organic moiety, first discovered by destructive distillation of the plant extract catechin [2]. Small amounts of catechol occur naturally in fruits and vegetables. Upon mixing the enzyme with the substrate and exposure to oxygen (as when a potato or apple is cut and left out), the colorless catechol oxidizes to reddish-brown melanoid pigments, derivatives of benzoquinone. Benzoquinone is said to be antimicrobial, which slows the spoilage of wounded fruits and other plant parts. Catechol is produced by the reversible two-electron, two-proton reduction of 1,2benzoquinone [3,4]. Hydroquinone (HQ) (1,4-dihydroxy benzene) is another phenolic compound coexisting with catechol in environmental samples. As an environmental pollutant it is toxic and can result in cancer like acute myeloid leukaemia [5]. High concentrations of HQ can incur headache, fatigue, tachycardia, decompensation, the damage to kidney, and even death. Long-term respiration in the atmosphere
⁎
containing low concentrations of HQ can incur cough, anorexia, nausea, spew, and pigmentation of the eye. Even low concentrations of CC in foods and cigarette smokes may cause mutagenesis and cancerous alteration [6–8]. These two isomers are widely used in industrial products such as cosmetics, pesticides, flavouring agents. Very poor biological degradation in environment makes catechol and hydroquinone is harmful to humans, even in a minute concentration are the major causes for environmental pollution [9]. These two isomers are included as environmental pollutants in the lists of Environmental Protection Agency (EPA) and the European Union (EU) [10]. Several analytical methods have been reported for the simultaneous determination of these isomers such as spectrophotometry [11], chemiluminescence [12], HPLC [13]. However, these methods are generally expensive and time consuming. Because of the same phenolic moieties, overlapping of the peaks at same oxidation potential, co-existence and their competitive adsorption at the electrode surface makes the relationship between the voltammetric response of CC and HQ and their concentration in the mixtures nonlinear [14]. Therefore, it is important to establish a simple and fast analytical method for sensitive and selective determination of HQ and CC in different matrices. To overcome these limitations, electrochemical methods such as
Corresponding author. E-mail address: [email protected] (B.E. Kumara Swamy).
https://doi.org/10.1016/j.jelechem.2018.07.021 Received 27 November 2017; Received in revised form 11 July 2018; Accepted 13 July 2018 1572-6657/ © 2018 Elsevier B.V. All rights reserved.
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voltammetric one's were extensively used because of their simplicity in the experimental procedure, rapid and quick response, excellent reproducibility, good stability, low cost and low detection limit [15–17]. In the present scenario carbon paste electrodes became one of the most commonly used electrodes due to its simple preparation, low cost, easy renewability, good sensitivity, low background current and fast response [18,19]. However, the absence of conducting binder in the CPE will lower the sensitivity of the detection system. Many chemically modified electrodes were prepared for the simple and simultaneous determination of isomers such as poly (crystal violet) graphene modified carbon ionic liquid electrode [20], poly (brilliant blue) modified carbon paste electrode [21], poly (glutamic acid) glassy carbon electrode [22], poly(glycine) modified glassy carbon electrode [23].However, polymer modified electrodes (PMEs) have received great attention in recent years, as the polymer film which is deposited onto the surface of the electrode by electropolymerisation has good stability, reproducibility, more active reaction sites, homogeneity, and strong adherence to the electrode surface [24,25]. The present work describes an electropolymerisation of an amino acid say glycine on the surface of carbon paste electrode by cyclic voltammetry. The fabricated electrode has the capacity to resolve the voltammetric peaks of catechol and hydroquinone in a binary mixture. A simple method was reported for the determination of dihydroxy benzene isomers.
Fig. 1. Cyclic voltammograms of preparation of poly (glycine) modified CPE.1 mM aqueous solution of glycine was taken in 0.2 M PBS of pH 7.0 at 5 cycles with scan rate 0.1 V s−1.
voltammograms. After the few cycles there is no increment in the peak height and it becomes more stable; which suggests polymerisation growth reached the saturation level [8,19,21]. The extent of thickness of the polymer film has a significant influence on the electrocatalytic activity of the modified electrode. It is well known that, as the thickness of the modifier layer increases the electron transfer rate decreases due to insufficient exposure of reactive sites on the electrode. The thickness can be controlled by varying the cyclic voltammetry parameters. Therefore 5 repetitive cycles were fixed as an optimum for the fabrication of poly(glycine) modified CPE. The probable electropolymerisation mechanism of glycine is described in Scheme 1.
2. Experimental section 2.1. Apparatus and reagents Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were performed in an analytical system model CHI-660c potentiostat (Electrochemical workstation, USA). The conventional three electrode electrochemical cell contained a saturated calomel electrode (SCE) as a reference, platinum wire as a counter electrode and the working electrode was either bare CPE or poly(glycine) modified CPE. The pH values were measured with a digital pH meter MK VI (systronics). All the obtained oxidation potential values are given versus SCE. Catechol (CC), hydroquinone (HQ) and glycine were purchased from Himedia. A stock solution of CC (25 × 10−4M), HQ (25 × 10−4M) and Glycine (25 × 10−3M) were prepared in double demineralized water. Graphite powder (50 μm particle size) was purchased from Loba and silicon oil (as binder) was purchased from Himedia. All chemicals were of analytical grade. The chemicals for the preparation of buffer solution were purchased from Merck. The 0.2 M phosphate buffer solution (PBS) was prepared by mixing standard stock solutions of 0.2 M NaH2PO4·H2O and 0.2 M Na2HPO4. All the solutions were freshly prepared prior to analysis. All the other solutions were prepared using double distilled water.
3.2. Electrochemical characterization of poly (glycine) modified CPE In order to evaluate the performance of the poly (glycine) modified CPE, potassium ferrocyanide[K4Fe(CN)6] was selected as an electrochemical probe. Fig. 2 shows electrochemical response of 1.0 mM [K4Fe (CN)6] at bare CPE (dashed line) and poly(glycine) modified CPE (solid line) in 1 M KCl at the scan rate 0.1Vs−1. A pair of redox peaks was observed for BCPE and with the modified CPE. The poly (glycine) MCPE shows lower peak potential difference (ΔEp), it was found to be 0.093 V and 0.101 V for bare and MCPE, respectively. As ΔEp is a function of electron transfer rate, lower the ΔEp means higher electron transfer rate. The result shows a dramatic change in the peak current at
2.2. Preparation of working electrodes The bare carbon paste electrode was prepared according to literature [19]. Electropolymerisation of glycine on the surface of carbon paste electrode was carried out by placing 1.0 mM glycine solution along with 0.2 M PBS of pH 7.0 in an electrochemical cell. The potential sweeping was maintained between −0.5 and +1.8 V at 0.1 V s−1 for 5 multiple cycles. Later the electrode was rinsed and washed with double distilled water prior to measurement. 3. Results and discussions 3.1. Optimisation condition for working electrode The modification procedure for the preparation of working electrode was mentioned in the Section 3.2. From the Fig. 1, it can be seen that, the anodic peak current enhances gradually in the repetitive cyclic
Scheme 1. Probable electropolymerisation mechanism of glycine. 731
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The heterogeneous rate constant (k0) values was determined from the experimental peak potential difference (ΔEp) data's, Eq. (2) was used for such voltammograms whose ΔEp values are greater than 10 mV [15,21].
ΔEp = 201.39 log (υ/k0) − 301.78
(2)
From the experimental ΔEp values as shown in the Table 1 and Eq. (2); the values of the k0 for the CC and HQ oxidation was determined for poly (glycine) modified CPE; the corresponding parameters are tabulated in Table 1. 3.4. The effect of concentration of catechol on poly (glycine) modified CPE The effect of concentration of CC was studied at poly (glycine) modified CPE in 0.2 M PBS pH 7.0 at the scan rate of 50 mV s−1. From the Fig. 5A it is clear that the peak potential of CC shift towards positive side with increasing the concentration of catechol in the range 0.2 × 10−4–2.0 × 10−4 M. The plot of Ipa versus concentration of CC shows linear relationship with regression equation of Ipa (10−5A) = 2.69(Co, 10−5 M/L) + 3.9(r2 = 0.9963) as in Fig. 5B. The limit of detection (LOD) and the limit of quantification (LOQ) were calculated by using the Eqs. (3) and (4) [21]. The values of LOD and LOQ were 0.16 μM and 0.55 μM, respectively. Therefore, the proposed method shows good results with improved detection limit than the results as reported in Table 2 [27–30], S is the standard deviation and M is the slope of calibration plot.
Fig. 2. Cyclic voltammograms of 1 mM potassium ferrocyanide at bare CPE (dashed line) and poly (glycine) MCPE (solid line) at scan rate of 0.05 V s−1 in 1 M KCl.
fabricated electrode [16,26].
3.3. Electrochemical investigation of catechol at the poly (glycine) modified CPE Fig. 3 shows the cyclic voltammograms obtained for 0.1 mM CC in 0.2 M PBS of pH 7.0 at poly(glycine) modified CPE (solid line) and bare CPE (dashed line) recorded at the scan rate of 50 mV s−1. At the bare CPE CC shows redox peaks with poor response and oxidation takes place at 0.215 V. On the other hand, at poly (glycine) modified CPE a significant enhancement in the current signals was observed and oxidation peak was located at 0.183 V. Therefore, the result suggests poly (glycine) modified CPE catalyses the oxidation process of CC. The oxidation mechanism of CC and HQ is shown in Scheme 2. The effect of applied scan rate for the oxidation of 0.1 mM CC in 0.2 M PBS of pH 7.0 was investigated with different scan rates in the range from 0.01–0.20 V s−1 at poly(glycine) modified CPE. The poly (glycine) modified CPE showed increase in the current signals with increasing scan rate as shown in Fig. 4A. The graph of anodic peak current (Ipa) versus scan rate (υ) was plotted (inset Fig. 4B), the result shows good linearity with correlation coefficient of r2 = 0.9981. Therefore, the results indicate that the electrochemical reaction of catechol at poly (glycine) modified CPE was adsorption-controlled [19].
LOD = 3S/M
(3)
LOQ = 10S/M
(4)
3.5. Electrocatalytic oxidation of hydroquinone at the poly (glycine) MCPE Fig. 6 shows the cyclic voltammograms obtained for the anodic oxidation of 0.1 mM HQ in 0.2 M PBS of pH 7.4 at bare CPE (dashed line) and poly (glycine) modified CPE (solid line) with the scan rate 50 mV s−1. At the bare CPE hydroquinone low redox current response and a broad voltammogram was obtained, the oxidation takes place at 0.075 V. On the other hand, the poly(glycine) modified CPE shows significant increase in the current signals yielding a sharp and sensitive voltammogram, the oxidation potential was observed at 0.0519 V. This minimization of over potential and refinement in the current response suggests the catalytic capability of fabricated electrode. The effect of scan rates on the oxidation of 0.1 mM HQ in 0.2 M PBS of pH 7.0 was investigated in the range 0.01–0.20 V s−1. The poly (glycine) modified CPE showed increase in the current signals with increasing scan rate according to Randles-Sevick's equation as shown in Fig. 7A. In order to confirm the electrode process, the graph of Ipa versus υ (inset Fig. 7B) was plotted and the result so obtained is in good linearity with correlation coefficient, r2 = 0.9965. The value suggesting that electrode process was controlled by adsorption. The effect of concentration of HQ was studied at poly (glycine) modified CPE in 0.2 M PBS pH 7.0 at the scan rate of 50 mV s−1. From Fig. 8A it is clear that the anodic peak current of hydroquinone was increased due to increasing in the concentration of HQ, the peak potential was shifted towards more positive side in the range 0.2 × 10−4–2.0 × 10−4 M. The plot of Ipa versus concentration of HQ (Fig. 8B) follows linear regression equation of Ipa (10−5A) = 1.8 (Co, 10−5 M/L) + 4.9 (r2 = 0.9946). The LOD and LOQ were found to be 0.20 μM and 0.66 μM, respectively. 3.6. Simultaneous determination of CC in presence of HQ at poly (glycine) modified CPE
Fig. 3. Cyclic voltammograms of 0.1 mM CC in 0.2 M PBS solution of pH 7.0 at bare CPE(dashed line) and poly (glycine) modified CPE (solid line) at scan rate of 0.05 V s−1.
It is quite difficult to determine electroactive species like CC and HQ simultaneously when they are present in a binary mixture. Because of 732
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Scheme 2. Mechanism of oxidation of catechol and hydroquinone. Table 1 Variation of the voltammetric parameters gathered from the plots shown in Fig. 4 and Fig. 7 as a function of the scan rate. υ inV/s
0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.12 0.14 0.16 0.18 0.20
Fig. 4. (A) Cyclic voltammograms of 0.1 mM CC in 0.2 M PBS solution of pH 7.4 at poly (glycine) modified CPE with different scan rate (a–o: 0.01 V s−1 to 0.20 V s−1) (B) Graph of anodic peak current versus scan rate(C) Graph of anodic peak current versus square root of scan rate.
ΔEp (V)
k0(mV/s)
Catechol (cc)
Hydroquinone (HQ)
Catechol (cc)
Hydroquinone (HQ)
0.04 0.06 0.07 0.08 0.09 0.01 0.12 0.13 0.15 0.15 0.17 0.20 0.21 0.22 0.23
0.05 0.06 0.07 0.09 0.10 0.12 0.13 0.15 0.16 0.17 0.19 0.22 0.23 0.26 0.27
31.5 88.8 159.7 251.9 350.9 462.6 583.1 712.6 850.1 996.5 1309.5 1651.4 2018.1 2407.5 2822.8
31.5 88.8 159.7 251.9 351.0 462.8 583.3 712.9 850.3 996.9 1310.2 1652.3 2019.4 2410.3 2825.7
obtained from the linearity were 55 mV/pH and 52 mV/pH for CC and HQ respectively. The results suggest that an equal number of protons and electrons are involved in the oxidation process [19]. This was consistent with the reported literature [21,31].
the same phenolic structure and similar oxidation potentials the discrimination in the voltammetric signal was not observed at bare CPE. Fig. 9 shows the cyclic voltammograms of simultaneous determination of 1 × 10−4 M CC, 1 × 10−4 M HQ in 0.2 M PBS of pH 7.0. The cyclic voltammogram obtained for the mixture of CC and HQ at bare CPE (dashed line) was not clearly defined and shows overlapped oxidation potential at 0.215 V. On the other side, the poly (glycine) modified CPE (solid line) shows well-defined oxidation peaks for CC and HQ located at 0.191 V and 0.0816 V, respectively and peak to peak separation is 0.109 V. This indicates that modified CPE act as a good electrochemical sensor for the simultaneous determination of poly (glycine) CC and HQ present in the binary mixture. The influence of PBS pH on the simultaneous determination of CC and HQ in a binary mixture was evaluated at poly(glycine) modified CPE by using cyclic voltammetric technique. Generally the oxidation was pH dependent and the oxidation peak potentials shifts towards more negative potential with increasing pH in the range 5.5 to 8.0 as shown in the Fig. 10A. The graph of Epa versus pH indicates the linear dependence of each other as in the inset Fig. 10B and C. The slopes
3.7. Interference study Differential pulse voltammograms were recorded due its higher current sensitivity and absence of non-faradic current. The determination of CC and HQ at poly (glycine) modified CPE in 0.2 M PBS of pH 7.0 was conducted as shown in the Fig. 11. At bare CPE overlapped peak was observed at 0.116 V. As poly (glycine) modified CPE resolved oxidation peaks into well-defined peaks located at 0.125 V for CC and 0.015 V for HQ, respectively. The peak to peak separation was 0.110 V. This result was more than enough for the determination of individual components. The analytical performance of the modified electrode can be evaluated by its capability of determining the species individually in the presence of interferents. It can be carried out by varying concentration of one species, while the other kept constant. From the Fig. 12A and B, 733
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Fig. 5. (A) Cyclic voltammograms of CC in 0.2 M PBS solution of pH 7.0 at poly (glycine) modified CPE with different concentration (a–j: 0.2 × 10−4 to 2.0 × 10−4 M) (B) Graph of anodic peak current versus concentration of CC.
Fig. 7. (A) Cyclic voltammograms of 0.1 mM HQ in 0.2 M PBS solution of pH 7.4 at poly (glycine) modified CPE with different scan rate (a–o: 0.01 V s−1 to 0.20 V s−1) (B) Graph of peak current versus scan rate (C) Graph of peak current versus square root of scan rate.
Table 2 Comparison of limit of detection with different modified electrodes and poly (glycine) modified CPE. Modified Electrodes
LDHf/GCE LRG/GCE Poly(Phenylalanine) MWNT/GCE MWCNT–NF–PMG/GCE Silsesquioxane/MCPE [Cu(Sal-β-Ala)(3,5-DMPz)2]/ MWCNTs/GCE Influence of micelles/GCE CNx/GCE Poly(calmagite) MCPE RGO–MWNTs Poly(glycine) modified CPE
Limit of detection (μM)
Method
References
CC
HQ
1.2 0.8 0.7 0.2 31.0 10 3.5
9.0 0.5 1.0 0.75 18.1 10 1.46
DPV DPV DPV DPV CV DPV DPV
[27] [28] [29] [30] [32] [33] [34]
3.0 2.71 2.55 1.8 0.16
8.0 1.20 1.70 2.6 0.20
DPV LSV CV DPV CV
[35] [36] [37] [38] This work
Fig. 8. (A) Cyclic voltammograms of HQ in 0.2 M PBS solution of pH 7.0 at poly (glycine) modified CPE at the scan rate of 0.05 V s−1 with different concentration (a–j: 0.2 × 10−4 to 2.0 × 10−4 M) (B) Graph of anodic peak current versus concentration of HQ.
Fig. 6. Cyclic voltammograms of 0.1 mM HQ in 0.2 M PBS solution of pH 7.0 at bare CPE (dashed line) and poly(glycine) modified CPE (solid line) at scan rate of 0.05 V s−1. Fig. 9. Cyclic voltammograms for simultaneous determination of 0.1 mM CC and 0.1 mM HQ at bare CPE (dashed line) and poly(glycine) modified CPE (solid line) at scan rate of 0.05 V s−1.
it can be seen that increase in the anodic peak current was linearly varied with CC concentration from 0.2–1.4 × 10−4 M, while keeping the concentration of hydroquinone 0.2 × 10−4 M constant. Similarly, 734
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Fig. 10. (A) Cyclic voltammograms of the poly (glycine) MCPE in 0.2 M PBS solution containing 0.1 mM CC and 0.1 mM HQ with different pH (a–f: 5.5 to 8.0) at scan rate of 0.05 V s−1 (B) The effect of pH on the peak potential response of 0.1 mM CC in 0.2 M PBS solution of pH 7.4 (C) The effect of pH on the peak potential response of 0.1 mM HQ in 0.2 M PBS solution of pH 7.0.
Fig. 13. (A) Differential pulse voltammograms of (a-g: 0.2 × 10−4 to 1.4 × 10−4 M) HQ in 0.2 M PBS of pH 7.4 in presence of 0.2 × 10−4 M CC at poly (glycine) MCPE (B) Graph of anodic peak current versus concentration of HQ.
by varying the HQ concentration from 0.2–1.4 × 10−4 M and keeping the concentration of CC 0.2 × 10−4 M constant, only the peak current of HQ was increased as shown in Fig. 13A and Fig. 13B. The results suggest that oxidation of both of the species occurs independently and the problem of interference was effectively resolved at the modified electrode. 4. Conclusion In the present study electropolymerisation of glycine was carried out on the surface of bare CPE and its application for the electrochemical determination of CC and HQ was investigated. The result shows that the poly (glycine) modified CPE not only exhibited strong electrocatalytic activity towards the oxidation of CC and HQ with the detection limit of 0.16 μM and 0.20 μM respectively, and but also resolved the overlapping peaks of CC and HQ into two well-defined peaks by cyclic voltammetric and differential pulse voltammetric techniques. Because of its electrocatalytic capability, selectivity, sensitivity and reproducibility the poly(glycine) modified CPE was very useful in the development of sensors for the simultaneous determination of catechol and hydroquinone in the field of electro-analytical chemistry.
Fig. 11. Differential pulse voltammogram obtained for 0.1 mM CC and 0.1 mM HQ in 0.2 M PBS solution of pH 7.4 at bare CPE (A) and poly (glycine) modified CPE.
References [1] H. Kotte, B. Gruendig, K.D. Vorlop, B. Strehlitz, U. Stottmeister, Methyl phenazonium-modified enzyme sensor based on polymer thick films for sub nanomolar detection of phenols, Anal. Chem. 6 (1995) 65–70. [2] Y.G. Sun, H. Cui, Y.H. Li, X.Q. Lin, Determination of some catechol derivatives by a flow injection electrochemiluminescent inhibition method, Talanta 53 (2000) 661–666. [3] H. Du, J. Ye, J. Zhang, X. Huang, C. Yu, A voltammetric sensor based on graphenemodified electrode for simultaneous determination of catechol and hydroquinone, J. Electroanal. Chem. 650 (2011) 209–213. [4] H.S. Han, J.M. You, H. Seol, H. Jeong, S. Jeon, Electrochemical sensor for hydroquinone and catechol based on electrochemically reduced GO-terthiophene-CNT, Sensors Actuators B 194 (2014) 460–469. [5] M. Gaskell, K.I.E.M. Luckie, P.B. Farmer, Comparison of the mutagenic activity of the benzene metabolites, hydroquinone and para-benzoquinone in the supF forward mutation assay: a role for minor DNA adducts formed from hydroquinone in benzene mutagenicity, Mutat. Res. 554 (2004) 387–398. [6] G.H. Zhao, M.F. Li, Z.H. Hu, H.X. Li, T.C. Cao, Electrocatalytic redox of hydroquinone by two forms of L-proline, J. Mol. Catal. B 255 (2006) 86–91. [7] M.A. Aziz, T. Selvaraju, H. Yang, Selective determination of catechol in the presence of hydroquinone at bare indium tin oxide electrodes via peak-potential separation and redox cycling by hydrazin, Electroanalysis 19 (2007) 1543–1546. [8] Y. Zhou, W. Tang, F. Dang, S. Chai, L. Zhang, Electrochemical characterization of poly-beryllon II modified carbon paste electrode and its application to selective determination of pyrocatechol and hydroquinone, Colloids Surf. B: Biointerfaces 118 (2014) 148–153.
Fig. 12. (A) Differential pulse voltammograms of (a-g: 0.2 × 10−4 to 1.4 × 10−4 M) CC in 0.2 M PBS of pH 7.4 in presence of 0.2 × 10−4 M HQ at poly (glycine) MCPE (B) Graph of anodic peak current versus concentration of CC.
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[9] Rekha, B.E.K. Swamy, P.S. Ganesh, Poly(alcianblue) modified carbon paste electrode for the determination of catechol in presence hydroquinone: a voltammetric study, Biosens. Bioelectron. 7 (2016) 217. [10] A.J.S. Ahammad, S. Sarker, M.A. Rahman, J.J. Lee, Simultaneous determination of hydroquinone and catechol at an activated glassy carbon electrode, Electroanalysis 22 (2010) 694–700. [11] A. Afkhami, H.A. Khatami, Indirect kinetic-spectrophotometric determination of resorcinol, catechol, and hydroquinone, J. Anal. Chem. 56 (2001) 429–432. [12] L.J. Zhao, B. Lv, H. Yuan, Z. Zhou, D. Xiao, A sensitive chemiluminescence method for determination of hydroquinone and catechol, Sensors 7 (2007) 578–588. [13] G. Marrubini, E. Calleri, T. Coccini, A.F. Castoldi, L. Manzo, Direct analysis of phenol, catechol and hydroquinone in human urine by coupled-column HPLC with fluorimetric detection, Chromatographia 62 (2005) 25–31. [14] P. Yang, Q. Zhu, Y. Chen, F. Wang, Simultaneous determination of hydroquinone and catechol using poly(p-aminobenzoic acid) modified glassy carbon electrode, J. Appl. Polym. Sci. 113 (2009) 2881–2886. [15] S.C. Avendano, G.A. Angles, M.T.R. Silva, G.R. Pina, M.R. Romo, M.P. Pardave, On the electrochemistry of dopamine in aqueous solution. Part I: the role of [SDS] on the voltammetric behavior of dopamine on a carbon paste electrode, J. Electroanal. Chem. 609 (2007) 17–26. [16] K.V. Harisha, B.E.K. Swamy, H. Jayadevappa, P.S. Ganesh, Electrochemical sensor for the determination of adrenaline in presence of acetaminophen at poly (alanine) modified carbon paste electrode: a cyclic voltammetric study, Biosens. Bioelectron. 7 (2016) 230. [17] P.S. Ganesh, B.E.K. Swamy, Cyclic voltammetric determination of catechol and hydroquinone at TX-100 modified carbon paste electrode, Anal. Bioanal. Chem. 8 (5) (2016) 615–628. [18] H.N.A. Mustafa, I.M. Isa, N.M. Ali, N. Hashim, M. Musa, S.A. Ghani, Amperometric detection of hydroquinone at modified ionic liquid graphene composite paste electrode, Int. J. Electrochem. Sci. 10 (2015) 9232–9245. [19] K.V. Harisha, B.E.K. Swamy, H. Jayadevappa, C.C. Vishwanath, Voltammetric determination of folic acid in presence of dopamine and ascorbic acid at poly(alanine) modified carbon paste electrode, Anal. Bioanal. Chem. 7 (2015) 454–465. [20] W. Sun, Y. Wang, Y. Lu, A. Hu, F. Shi, Z. Sun, High sensitive simultaneously electrochemical detection of hydroquinone and catechol with a poly(crystal violet) functionalized graphene modified carbon ionic liquid electrode, Sensors Actuators B Chem. 188 (2013) 564–570. [21] P.S. Ganesh, B.E.K. Swamy, Simultaneous electroanalysis of hydroquinone and catechol at poly(brilliant blue) modified carbon paste electrode, J. Electroanal. Chem. 756( (2015) 193–200. [22] L. Wang, P. Huang, J. Bai, H. Wang, L. Zhang, Y. Zhao, Direct simultaneous electrochemical determination of hydroquinone and catechol at a poly(glutamic acid) modified glassy carbon electrode, Int. J. Electrochem. Sci. 2 (2007) 123–132. [23] L. Wang, P. Huang, H. Wang, J. Bai, L. Zhang, Y. Zhao, Electrocatalytic response of hydroquinone and catechol at polyglycine modified glassy carbon electrode, Int. J. Electrochem. Sci. 2 (2007) 216–225. [24] R.F. Rane, C.D. Blaha, Detection of catecholamines in brain tissue:surface-modified
[25] [26]
[27]
[28]
[29]
[30]
[31]
[32]
[33]
[34]
[35]
[36]
[37]
[38]
736
electrodes enabling in vivo investigations of dopamine function, Langmuir 6 (1990) 56–65. A.G. Ewing, M.A. Dayton, R.M. Wightman, Pulse voltammetry with microvoltammetric electrodes, Anal. Chem. 53 (1981) 1842–1847. O. Gilbert, B.E.K. Swamy, U. Chandra, B.S. Sherigara, Simultaneous detection of dopamine and ascorbic acid using polyglycine modified carbon paste electrode: a cyclic voltammetric study, J. Electroanal. Chem. 636 (2009) 80–85. M. Li, F. Ni, Y. Wang, S. Xu, D. Zhang, S. Chen, L. Wang, Sensitive and facile determination of catechol and hydroquinone simultaneously under co-existence of resorcinol with a Zn/Al layered double hydroxide film modified glassy carbon electrode, Electroanalysis 21 (13) (2009) 1521–1526. T. Lai, W. Cai, W. Dai, J. Ye, Easy processing laser reduced graphene: a green and fast sensingplatform for hydroquinone and catechol simultaneous determination, Electrochim. Acta 138 (2014) 48–55. L. Wang, P. Huang, J. Bai, H. Wang, L. Zhang, Y. Zhao, Simultaneous electrochemical determination of phenol isomers in binary mixtures at a poly(phenylalanine) modified glassy carbon paste electrode, Int. J. Electrochem. Sci. 1 (2006) 403–413. H.Q.C. Zhang, Simultaneous determination of hydroquinone and catechol at glassy carbon electrode modified with multi-wall carbon nanotubes, Electroanalysis 17 (10) (2005) 832–838. P.S. Ganesh, B.E.K. Swamy, Simultaneous electroanalysis of norepinephrine, ascorbic acid and uric acid using poly(glutamic acid) modified carbon paste electrode, J. Electroanal. Chem. 752 (2015) 17–24. Y. Umasankar, A.P. Periasamy, S.M. Chen, Electrocatalysis and simultaneous determination of catechol and quinol by poly(malachite green) coated multi-walled carbon nanotube film, Anal. Biochem. 411 (2011) 71–79. P.S.D. Silva, B.C. Gasparini, H.A. Magosso, A. Spinelli, Electrochemical behaviour of hydroquinone and catechol at a silsesquioxane-modified carbon paste electrode, J. Braz. Chem. Soc. 24 (4) (2013) 695–699. L.A. Alshahrani, X. Li, H. Luo, L. Yang, M. Wang, S. Yan, P. Liu, Y. Yang, Q. Li, The simultaneous electrochemical detection of catechol and hydroquinone with [Cu (Sal-β-Ala)(3,5-DMPz)2]/SWCNTs/GCE, Sensors 14 (2014) 22274–22284. J. Peng, Z.N. Gao, Influence of micelles on the electrochemical behaviours of catechol and hydroquinone and their simultaneous determination, Anal. Bioanal. Chem. 384 (2006) 1525–1532. J. Dong, X. Qu, L. Wang, C. Zhao, J. Xu, Electrochemistry of nitrogen-doped carbon nanotubes (CNx) with different nitrogen content and its application in simultaneous determination of dihydroxybenzene isomers, Electroanalysis 20 (18) (2008) 1981–1986. P.S. Ganesh, B.E.K. Swamy, Rekha, Electroanalysis of catechol in presence of hydroquinone at poly(calmagite) modified carbon paste electrode: a voltammetric study, Sci. Lett. 5 (2016) 236. F. Hu, S. Chen, C. Wang, R. Yuan, D. Yuan, C. Wang, Study on the application of reduced graphene oxide and multiwall carbon nanotubes hybrid materials for simultaneous determination of catechol, hydroquinone, p-cresol and nitrite, Anal. Chim. Acta 724 (2012) 40–46.