Silver nanoparticles/poly(L-cysteine) nanocomposite modified pencil graphite for selective electrochemical measurement of guaifenesin in real samples

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

“…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. The electrical contact with the potentiostat is provided by a metallic (copper) wire wrapped arround the end of the mine, which is not exposed to the analyzed solution.…”

“…In some cases, electrodeposition (e.g., AuNPs) and electropolymerization (e.g., polypyrrole [37], and poly(L-methionine [130]) on the PGE surface were achieved in one single step by CV, with other modification procedures comprising both cyclic voltametric and potentiostatic steps [53,91,129,131].…”

“…The electro-oxidation response of guaifenesin for the bare PGE and PGE modified with AgNPs/P(L-cys) was evaluated by CV and DPV. For the unmodified PGE, the guaifenesin alcohol group gave a weak oxidation signal whose peak current increased, and its potential shifted in the negative direction after the electrode surface covering by P(L-cys) and by P(L-cys)/AgNPs due to the analyte adsorption through the hydrogen bonding interaction of guaifenesin -OH groups and the P(L-cys) film and the AgNPs' electrocatalytic effect on the resulting current, respectively [53]. The examples could be continued, but generally, it can be concluded that PGE modification generates higher peak currents, yielding more sensitive determinations, and in some cases, a potential shift toward lower values was observed, indicating that the electrode process took place easier.…”

“…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].…”

“…CV carried out at different scan rates was most often employed to calculate the electroactive surface area (A ea ) of bare or different modified electrodes while considering the slope of the regression equation corresponding to the I p = f(v 1/2 ) plot, where I p (A) repre-sents the peak current and v is the potential scan rate (V/s) [16,20,38,39,41,[43][44][45][46][47][48][49]53,56,59,64,67,72,74,82,85,87,88,106,[124][125][126]128,141].…”