Paracetamol Sensing with a Pencil Lead Electrode Modified with Carbon Nanotubes and Polyvinylpyrrolidone

Abstract

The determination of paracetamol is a common need in pharmaceutical and environmental samples for which a low-cost, rapid, and accurate sensor would be highly desirable. We develop a novel pencil graphite lead electrode (PGE) modified with single-wall carbon nanotubes (SWCNTs) and polyvinylpyrrolidone (PVP) polymer (PVP/SWCNT/PGE) for the voltammetric quantification of paracetamol. The sensor shows remarkable analytical performance in the determination of paracetamol at neutral pH, with a limit of detection of 0.38 μM and a linear response from 1 to 500 μM using square-wave voltammetry (SWV), which are well suited to the analysis of pharmaceutical preparations. The introduction of the polymer PVP can cause dramatic changes in the sensing performance of the electrode, depending on its specific architecture. These effects were investigated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). The results indicate that the co-localization and dispersion of PVP throughout the carbon nanotubes on the electrode are key to its superior electrochemical performance, facilitating the electrical contact between the nanotubes and with the electrode surface. The application of this sensor to commercial syrup and tablet preparations is demonstrated with excellent results.

Recent Developments in Voltammetric Analysis of Pharmaceuticals Using Disposable Pencil Graphite Electrodes

“…Electrical contact with the instrument is realized by means of a conductive wire which was soldered or wrapped to the metallic part of the mechanical pencil holder [9,19,21,22,[24][25][26][27][28][29][30][31][32][33][34][35][36][37] (Figure 1a). A micropipette tip [38], an insuline syringe [39], a glass cappilary [40,41], or a plastic [16,[42][43][44][45][46] (Figure 1b) or Teflon tube [47][48][49][50][51][52] (Figure 1c,d) can also act as holder. An araldite mixture (epoxy resin, 1:1) [16,41,[43][44][45], bentonite [38,39], or cyanoacrylate glue [40] was used to fix the graphite lead into the support.…”

“…A micropipette tip [38], an insuline syringe [39], a glass cappilary [40,41], or a plastic [16,[42][43][44][45][46] (Figure 1b) or Teflon tube [47][48][49][50][51][52] (Figure 1c,d) can also act as holder. An araldite mixture (epoxy resin, 1:1) [16,41,[43][44][45], bentonite [38,39], or cyanoacrylate glue [40] was used to fix the graphite lead into the support. Other PGEs were obtained by covering a part of the graphite lead with nail polish [53] or with Teflon tape [20,[54][55][56][57][58][59][60][61][62][63][64][65] (Figure 1e), leaving a constant length and area of nacked pencil mine to act as an electroative surface.…”

“…Sometimes, the graphite lead electrode is polished with an alumina slurry [25,41,47,59,67], on sandpaper with different granulometrics [40,42,68], on emery paper [41,[49][50][51][52]69] followed by a butter sheet [16,45], on butter paper [39], or on weighing paper [20,57,58,62,70]. Yen et al [71] reported that amoxicicllin presented a better electrochemical response at the PGE mechanically treated with polishing paper in comparison with the original electrode.…”

“…Other modified PGEs were manufactured by dip [17,61,69,87,88,90,92,127,132,133] or spin coating [48,[50][51][52]125,126,134]. Drop coating was applied to produce Mo 5 O 8 /PGE [34], Trypan blue-modified PGEs [44], different CNT-modified PGEs [47,57,58,68], or PGEs covered with various modifiers [41,49,62,65,135]. After that, the modified PGE was dried either in air [35,48,52,66,68,69,90,136] or in other well-established conditions (e.g., in a desiccator [50] or at a certain temperature [125,137]).…”

“…The electrochemical characterization of bare and modified electrodes was usually performed by CV [87,88,117,124,125,129] and electrochemical impedance spectroscopy (EIS) using [Fe(CN) 6 ] 3−/4− as a redox probe and KCl as a supporting electrolyte [17,20,37,41,43,45,47,53,56,57,59,[63][64][65]69,80,85,87,90,105,117,124,125,127,131,132,136,[141][142][143]147], but [Ru(NH 3 ) 6 ] 3+/2+ was also used [38].…”