A new voltammetric method was developed for simultaneous determination of lidocaine hydrochloride (LH) and its toxic metabolite (2, 6-dimethylaniline (DMA)) based on their oxidation and adsorption on C18 silica modified carbon paste electrode (SMCPE). Several experimental factors including the effect of pH, scan rate, percentage of silica, accumulation potential and time were studied and the optimum conditions were found to be: pH 11 ± 0.10 using Britton Robinson buffer, 100 mV/s scanning rate, −0.6V accumulation potential, 150 s accumulation time and 5% C18 silica. Under the optimized conditions, applying square wave voltammetry (SWV) displayed two signals for DMA and LH at 0.56 and 0.87 V, respectively. The method revealed satisfactory results in terms of linearity (7.94 × 10⁻⁶ to 1.07 × 10⁻⁴ M) for LH and (1.20 × 10⁻⁶ to 1.07 × 10⁻⁵ M) for DMA, accuracy, and precision. The limit of detection was found to be 2.19 × 10⁻⁶ and 2.15 × 10⁻⁷ M for LH and DMA in pure forms, respectively. The developed SWV method was further applied for the assay of LH in its pharmaceutical dosage form and DMA in spiked milk samples.

The prevalence of cancer worldwide has prompted efforts to develop and produce a range of electrochemical biosensors for cancer diagnosis. Efficient cancer diagnosis can be enhanced by the sensitive detection of biomarkers, which can also lower the cost of medical diagnostics. Neuroblastoma is an embryonic cancer arising from neural crest stem cells and is considered the most common malignancy in infants and the extracranial solid tumor in children. In this paper, we describe the construction of a nanoparticle-modified electrochemical sensor for detecting and quantifying homovanillic acid (HVA), a biomarker for neuroblastoma. The electrooxidation of HVA was studied at a carbon paste electrode (CPE) modified with nickel-doped zinc oxide nanoparticles (Ni-ZnO NPs). The use of these nanoparticles enhanced electrochemical sensitivity and the electrocatalytic activity. The differential pulse voltammetric response of HVA was found to be linear in the concentration range of (3.96 × 10⁻⁶ to 3.83 × 10⁻⁵ M) with a lower detection limit of 1.01 × 10⁻⁶ M. The electrode demonstrated good stability in the HVA determination process, with a minor decrease in response after 10 weeks. The proposed sensor was successfully applied to determine HVA in a urine sample with a good detection result and a worthwhile biological impact.

During cancer treatment, doses must be carefully administered and monitored to guarantee efficacy and minimize side-effects. A potentiometric sensor was developed for the direct real-time assay of a widely used antineoplastic drug (vinblastine (VB)) in plasma samples. Membrane cocktails were drop-casted over a glassy-carbon electrode coated with a lipophilic conducting polymer (polyaniline). The study investigated five cation exchangers, five plasticizers (of different polarities and dielectric constants), and four ionophores with different physicochemical characters on the sensor performance. The study substantiates a data-driven selection of the optimum membrane recipe. The latter included sodium tetraphenylborate as an ion exchanger, dioctylphthalate as a plasticizer, and hydroxypropyl-β-cyclodextrin as ionophore. The membrane proved a near-Nernstian slope of 37.5 mV per decade, a LOQ of 2.99 × 10⁻⁶ M, and a stable fast response. The selectivity study proved poor responses to common physiological ions. The developed sensor was used for the determination of VB in its pure powder form, marketed formulation, and plasma samples. The fast and direct sensor response enables a wide range of applications in quality control laboratories and clinical studies.

2,6-Dimethylaniline (DMA) and o-toluidine (TOL) are considered as toxic impurities and carcinogenic metabolites as well as hydrolytic products upon degradation process for lidocaine (LD) and prilocaine (PR), respectively. The presence of such impurities above the permutable limits can adversely affect health and cause severe complications. Three different separation techniques, namely, high-performance liquid chromatography (HPLC), capillary zone electrophoresis (CZE), and thin-layer chromatography (TLC), were applied for the selective determination of the toxic compounds DMA and TOL and their intact drugs, LD and PR, respectively. The proposed HPLC method was carried out on Inertsil ODS 3 column (50 mm × 4.6 mm, 5 μm), utilizing a green mobile phase consisting of ethanol and 34 mM disodium hydrogen phosphate (20:80, v/v; pH = 6 adjusted using o-phosphoric acid). The flow rate was 1 mL min−1 with UV detection at 220 nm. The CZE separation was performed using 50 mM monobasic sodium phosphate (pH = 2.5), an...