Because of their large surface area and conductivity, some inorganic materials have emerged as good candidates for the trace-level detection of pharmaceutical drugs. In the present work, we demonstrate the detection of an anticancer drug (regorafenib, REG) by using an electrochemical sensor based on a nanocomposite material. We synthesized a zirconia-nanoparticle-decorated reduced graphene oxide composite (ZrO2/rGO) using a one-pot hydrothermal method. Reduction of the graphene oxide supports of the Zr2+ ions with hydrazine hydrate helped in preventing the agglomeration of the zirconia nanoparticles and in obtaining an excellent electrocatalytic response of the nanostructure ZrO2/rGO-based electrochemical sensor. Structural and morphological characterization of the nanostructure ZrO2/rGO was performed using various analytical methods. A novel regorafenib (REG) electrochemical sensor was fabricated by immobilizing the as-prepared nanostructure ZrO2/rGO on to a glassy carbon electrode (GCE). The resulting ZrO2/rGO/GCE could be used for the rapid and selective determination of REG in the presence of ascorbic acid and uric acid. The ZrO2/rGO/GCE showed a linear response for the REG analysis in the dynamic range 11–343 nM, with a remarkable lower detection limit and limit of quantifications of 17 and 59 nM, respectively. The newly developed sensor was used for the accurate determination of REG in both serum samples and pharmaceutical formulations, with satisfactory results.

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The electrochemical has been constructed based on Co 3 O 4 /rGO nanocomposite in presence of CTAB modified carbon paste electrode (CPE) and was developed for the simultaneous determination of dopamine, uric acid and folic acid at physiological pH 7.0 (PBS, 0.1 M). The physico-chemical analysis of nanocomposite was characterized by FT-IT, PXRD, SEM, TEM and EDX. The modified sensor showed well defined and stable reversible peak couple in both alkaline and aqueous solution. From the differential pulse voltammetry (DPV), the electrochemical sensor showed excellent electrocatalytic activity for the oxidation of dopamine, limit of detection (LOD) and limit of quantification (LOQ) of DA are calculated to be 2.8 µM and 10 µM, respectively. The Co 3 O 4 /rGO/CTAB MCPE showed an efficient electron mediating behavior with well defined oxidation peak potentials between DA to UA and UA to FA were 0.12 V and 0.39 V, respectively. From the cyclic voltammetry the results obtained for the linear calibration plots and the limit of detection of DA, UA and FA were calculated to be 7 µM, 94 µM and 19 µM, respectively. The developed sensor was successfully employed to sensing of DA in real samples.

A carbon paste electrode (CPE)/Cu nanowire (Cu NW)/poly(1-ethyl-3-methylimidazolium methyl sulfate) based sensor was successfully fabricated by the electro-polymerization of 1-ethyl-3-methylimidazolium methyl sulfate (EMIMS) onto the surface of Cu nanowires-modified carbon paste electrode. The morphology and chemical nature of Cu NWs were characterized by FTIR, FE-SEM, TEM, XRD techniques. The CPE/CuNWs/poly(EMIMS) showed an electrocatalytic activity toward the determination of etilefrine hydrochloride (ET-HCl) in the 0.11 M buffer solution of phosphate at pH 7.0. The CPE/CuNWs/poly (EMIMS) showed an excellent limit of detection (LOD) 2.3 μM over the linear dynamic range of 0.1 to 1.3 μM. The prepared CPE/CuNWs/poly(EMIMS) has exhibited high stability, good sensitivity, and low detection limit for the determination of ET-HCl. The validity of this advanced method was checked by applying in the blood plasma samples, with satisfactory results. This novel CPE/CuNWs/poly(EMIMS) can be an attractive material for the applications in biomedical and sensor fields.