Elsevier

Analytica Chimica Acta

Volume 1168, 11 July 2021, 338595
Analytica Chimica Acta

Interference-free electrocatalysis of p-chloro meta xylenol (PCMX) on uniquely designed optimized polymeric nanohybrid of P(EDOT-co-OPD) and fMWCNT modified glassy carbon electrode

https://doi.org/10.1016/j.aca.2021.338595Get rights and content

Highlights

  • Novel polymeric nanohybrid of P(EDOT-co-OPD) with fMWCNT modified working electrode.

  • Multivariable factorial design used to optimize the sensing polymeric nanohybrid matrix.

  • Interference-free electrocatalysis of PCMX without using any biomaterials.

  • Differential pulse voltammetric analysis to quantify PCMX in environmental samples.

  • Excellent sensitivity, reproducibility, and stability of the sensing matrix for detection of PCMX.

Abstract

p-Chloro-meta-Xylenol (PCMX) is an environmentally hazardous phenolic compound having biocidal and antiseptic activity. Very few research publications addressed monitoring this contaminant. This paper presents a rapid sensing system to quantify it in waste water samples. The electrochemical activity of PCMX was exploited through a unique polymeric nanocomposite modified transducer for its quantification. Poly[(3,4-Ethylenedioxythiophene)-co-(o-phenylenediamine)] [P(EDOT-co-OPD)] was deposited through one-step electropolymerization technique on the glassy carbon electrode (GCE) modified by functionalized multi-wall carbon nanotubes (fMWCNTs). An optimized combination of these constituents was evaluated using response surface methodology (RSM) based Box-Behnken experimental design. This maximized the response for PCMX using differential pulse voltammetry (DPV). The sensing matrix was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The structural and morphological study of the modified film was conducted by Fourier transform-infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), and field emission scanning electron microscope (FESEM). The anodic peak current could be read from a wide range of 0.5–225 μM calibration curve with a detection limit of 0.2545 μmol L−1. Interestingly this work did not use any biomaterial in the modification but achieved interference-free response with excellent selectivity, sensitivity (0.4668 μA μM−1 cm−2), reproducibility (RSD = 2.2%), and repeatability. The sensing platform showed good stability (85.7%) of 3 months even after 150 times repetitive use. Its applicability for real samples was established by good correlation with standard methods.

Introduction

Para-Chloro-meta-Xylenol (PCMX) or 4-chloro-3,5-dimethylphenol is an aromatic organic pollutant containing phenol. It is widely used as an antibacterial preservative in cosmetic formulations. Pharmaceutical wastes mainly contain a considerable amount of PCMX that may cause severe toxicity in aquatic life (LCfish-0.36 mg/L, ECwater flea - 7.7 mg/L). The LD50 values for rat and fish are 3.83 g/kg (about 24.55 mM) and 0.36 mg/L (∼2.31 μM), respectively. The contamination of waste-water with PCMX is mainly due to its release during the manufacture of pharmaceutical products. It is well known that phenolic compounds and their derivatives are emerging as priority organic contaminants that are commonly detected in the surface as well as groundwater. The extensive use and constant release practices of these pollutants have led to non-negligible long-term ecological risks to aquatic organisms, plants, and humans. Chlorophenols are recognized as environmentally hazardous (toxicity category I) substances by US Environmental Protection Agency (EPA) due to their high toxicity including estrogenic, mutagenic, carcinogenic effects, and poor biodegradation [[1], [2], [3], [4], [5]]. Chlorophenols in water bodies may easily penetrate through the membranes and plant surface layers. Presently chromatographic techniques such as high performance liquid chromatography (HPLC), gas chromatography-mass spectroscopy (GC/MS) are mainly used for the quantification of residual chlorophenols in real samples (agricultural, pharmaceutical). However, these require extensive time-consuming sample preparation steps, involve high cost, and poor selectivity [6]. On the other hand, electrochemical techniques have received great attention for their inherent simplicity, good reliability, high sensitivity, cost-effectiveness and miniaturized instrumentations for rapid detections of electro-active compounds [[7], [8], [9], [10], [11]]. Nanomaterials such as multiwalled carbon nanotubes (MWCNTs) are widely applied in fabrication of highly sensitive electrochemical sensors since these offer large surface area, high thermal, electrical and chemical stabilities [[11], [12], [13], [14], [15]]. The electrodeposition of fMWCNTs on conductive polymers enhances the capacitive current density during the anodic oxidation process [11,16,17]. This may also improve the electrical, and mechanical properties of the native polymer [18]. Several works have been reported on the application of MWCNTs in fabricating electrochemical sensors for phenolic compounds e.g. bisphenol A, catechol, 2-chlorophenol, 4-chlorophenol [[19], [20], [21]]. Conducting polymers e.g. polypyrrole (PPy), poly (3,4-ethylenedioxythiophene) (PEDOT), polyaniline (PANI) and polyfuran (PFu) exhibited excellent electrical, optical properties with good conductivity and stability [17,22]. Again, presence of dioxyalkylene bridging group in PEDOT greatly enhances electrochemical stability and conductivity [17,23]. Another polyaniline derivative semiconductive polymer namely, poly (o-phenylenediamine) (P-OPD) is widely used in various applications such as sensors, microelectronics, corrosion protection of metals, etc. [11,18,24]. It helps in enhancing the stability and permselectivity of the modified surface for good co-adhesion activity [11,24]. A novel nanocomposite of PPD and oxidized MWCNTs has been reported for analysis of biphenyl and polycyclic aromatic hydrocarbon [18]. In our previous study, fMWCNT modified nano-gold doped PPD (Au-PPD) film exhibited excellent permselectivity and surface adhesion for the fabrication of third generation xanthine biosensor with good reproducibility, repeatability, sensitivity, specificity, and stability [11]. However, there are only two reports published so far, on electrochemical sensing of PCMX which used reduced graphene oxide paste electrode (TRGOPE) and graphene carbon paste electrode (GCPE) [25,26]. In this paper, an effort is made to address this unexcavated research area to develop a unique nanohybrid polymeric matrix using fMWCNT, PEDOT and PPD for detection of PCMX.

Again, multivariable statistical optimization has been adopted to maximise response. Statistical optimization helps reduce the number of experiments to be conducted to achieve maximum response in processes involving number of variables [[26], [27], [28]]. The application of statistical designing is, however, rare in electrochemical sensing applications [21]. Response surface methodology (RSM) is a statistical method that is a fast and effective multiparameter optimization process. RSM interprets the interactions among the most important operational parameters and finds optimum conditions for the response [[27], [28], [29]]. There are only a few research works reported involving RSM for optimization of voltammetric response [[30], [31], [32], [33]]. There is no report available for the synthesis of one-step copolymerization of 3,4-ethylenedioxythiophene (EDOT) and o-phenylenediamine (OPD). This unique polymeric composite imparts good conductivity as well as surface adhesion for better stability of the sensing platform. In this research, fMWCNTs were first electrodeposited on the bare GCE followed by electro-deposition of polymer matrix, P(EDOT-co-OPD). The optimal concentrations of the components of the polymeric nanocomposite were evaluated using RSM to achieve the highest response for quantification of PCMX in real samples.

Section snippets

Chemicals and apparatus

p-Chloro meta xylenol (PCMX), 3,4-Ethylenedioxythiophene (EDOT), multiwall carbon nanotubes (MWCNT), o-phenylenediamine (OPD) were procured from Sigma Aldrich, USA. Potassium ferrocyanide (K₄[Fe(CN)₆]·3H₂O), potassium ferricyanide (K3 [Fe(CN)6]) and para-toluene sulphonic acid (p-TSA) were purchased from E Merck (Germany). Acetonitrile (ACN), potassium dihydrogen phosphate (KH2PO4), dipotassium hydrogen phosphate (K2HPO4), hydrogen chloride acid (HCl), nitric acid (HNO3), sulfuricacid (H2SO4),

Optimization of operational variables by the Box-Behnken experimental design

Table 2 shows the DPV response for 0.5 M PCMX at different combinations between individual components of the polymeric nanocomposite. The multiple regression analysis was performed to fit the experimental data with the polynomial [[26], [27], [28]]. The relative impact between the significant process variables with respect to the response in coded values could be expressed by the following second-order polynomial equation:Current=+19.57+16.26A+6.14B+1.78C9.66AB+6.03AC+3.47BC+4.99A2+29.69

Conclusion

The fMWCNT modified uniquely fabricated polymeric composite of P(EDOT-co-OPD) glassy carbon electrode was successfully developed for quantification of [PCMX]. This novel P(EDOT-co-OPD)/fMWCNT/GCE electrode produced interference-free response for sensing PCMX. The most important feature of this sensor was that no biomaterial e.g. enzyme was used for the modification of the electrode. Moreover, RSM based Box-Behnken experimental design was applied on the modification process to achieve optimum

CRediT authorship contribution statement

Bhanupriya Brahma: Acquisition of experiments, Methodology, Data curation, Formal analysis, Investigation, Software, Writing – original draft, preparation. Sarani Sen: Conceptualization, and design of study, Formal analysis, Investigation, Software, Writing – original draft, preparation. Priyabrata Sarkar: Supervision, Resources, Validation, Writing – review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

The author (BP) acknowledges University Grant Commission, Delhi and Ministry of Tribal Affairs, India, for providing fellowship (Award letter no: F1-17.1/2014-15/RGNF-2014-15-ST-ASS-80000). This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

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