Pt Nanospheres Decorated Graphene-β-CD Modified Pencil Graphite Electrode for the Electrochemical Determination of Vitamin B6

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

“…Energydispersive X-ray analysis (EDX or EDS) is an elemental analysis technique giving information about the chemical composition of a material, so this was frequently applied in the PGE modification process to reveal the elemental distribution by mapping each component [10,17,20,48,87,110,120,124,126,131,132,134,146,148,150], thus confirming the presence of the modifier(s) on the electrode surface in different steps [38,49,52,53,[61][62][63]68,69,130,142,143,145,147]. X-ray photoelectron spectroscopy (XPS), also known as electron spectroscopy for chemical analysis (ESCA), which provides information about the chemical composition of the material and the chemical state of the contained elements was sometimes used as a complementary technique to confirm the existence of certain materials at the PGE's surface [10,128,134,144]. X-ray diffraction (XRD) analysis was applied to gain structural information (crystallinity) about bare or modified PGEs.…”

“…The reduction signal of vitamin B12 (E p ~−0.80 V) and of vitamin B9 (E p ~−0.60 V) constituted the basis of their determination by DPV for the bare PGE (Table 1) [55] and by CS-DPV for the CNDs/MIP(PABSA)/PGE [123], respectively, while Sangeetha and Narayanan [144] developed a PGE modified with two mediators, Azure A and nickel hexacianoferrate, with electrocatalytic activity for the oxidation of the antioxidant butylated hydroxyanisole and the reduction of vitamin B2, respectively. Vitamin K1 quantification by SWV for the 2-A-5-CBP/AgNPs/ET-PGE [60] and celecoxib by DPV for the fMWCNT/MIP/PGE [122] were also based on their reduction signals (Table 3).…”

“…The graphite lead modification with f-MWCNTs and AuNPs resulted in a specific electroactive surface that was 6.66 times larger [61], and the CNDs/MIP(PABSA)/PGE developed for folic acid determination presented an electroactive surface area enhanced 9.26 times vs. the bare PGE [123]. Likewise, A ea increased in the following order: PGE (1.121 cm 2 ), β-CD-G/PGE (2.578 cm 2 ), Pt/β-CD-G/PGE (3.420 cm 2 ) and PGE (15.29 cm 2 ), P(SA)PGE (17.93 cm 2 ), NiONPs/PGE (22.25 cm 2 ), and NiONPs/P(SA)/PGE (35.45 cm 2 ) in the case of the modified PGEs recently developed for vitamin B6 [144] and avanafil and nimodipine [151] analysis, respectively.…”

“…Thus, the larger semicircle indicates a high interfacial electron transfer resistance, whereas a small semicircle indicates a lower resistance, increased conductivity, and faster electron transfer. Usually, the ET [43,56,80] or modified electrodes employed [20,36,37,[45][46][47]53,57,59,61,[63][64][65]67,68,85,90,92,105,110,113,117,130,132,136,[141][142][143][144]147,148] in pharmaceutical quantification presented a much lower Rct and thus a higher electron transfer capability in comparison with the bare PGE or the electrodes modified during the different steps of the manufacturing process. For example, EIS measurements emphasized that by covering the PGE with MIP/sol-gel, the Rct increased due to the surface passivation and decreased after potentiostatic deposition of N-doped graphene [127], AuNPs [91], or phosphotungstic acid/reduced graphene oxide (PWA/rGO) [65] due to the electronconducting properties of the nanomaterials.…”

“…The modifications of the PGEs either in the final form or during the intermediate steps involving the deposition of various materials [53,60,69,85,86,127,130,131,143] must be proven by surface analysis using non-destructive techniques like scanning electron microscopy (SEM) [41,46,52,60,67,87,88,106,119,124,127,133,[144][145][146]151], field effect SEM (FE-SEM) [108,110,128,134,142,150], transmission electron microscopy (TEM) [52,87,134,144,146], and atomic force microscopy (AFM) [36,37,109,110]. These techniques, either alone or in combination, give valuable information about the surface morphology (e.g., texture and distribution of the materials [50,62,65,72,90,…”