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Solid contact ion selective electrodes are extensively utilized owing to their marvelous performance over traditional liquid contact ones. The main drawback of those solid contact electrodes is aqueous layer formation which affects their constancy. Herein and to overcome this common drawback, a carbon paste electrode containing poly(3,4-ethylenedioxythiophene) was constructed and used for determination of probenecid at variant pH values. This modification decreased the potential drift down to 0.8 mV/h and improved its stability over 30 days. A Nernstian slope of − 57.8 mV/decade associated with a linear range of 1.0 × 10−6–1.0 × 10−2 mol/L was obtained. The modified carbon paste electrode successfully detected up to 8.0 × 10−7 mol/L probenecid. Results of this modified carbon paste electrode were also compared to unmodified one.

Simple, sensitive and accurate stability indicating spectrophotometric methods have been developed for the simultaneous determination of probenecid, colchicine as well as colchicine degradation product in their ternary mixture. Probenecid was firstly assayed using the double divisor ratio spectra derivative method. On the other hand, three spectrophotometric methods, namely: ratio difference, derivative ratio and mean centering of ratio spectra, have been suggested for the simultaneous quantification of colchicine and its degradation product. The obtained calibration curves were linear at 2.5–30.0 μg/mL, 0.5–25.0 μg/mL and 1.0–13.0 μg/mL for probenecid, colchicine and colchicine degradation product, respectively. The investigated methods were validated in accordance with the International Council for Harmonisation guidelines and were effectively used for quantification of probenecid and colchicine in their bulk powders and combined pharmaceutical dosage form.

A simple electrochemical procedure was developed for the electrochemical determination of Loperamide hydrochloride (LOP). A square wave voltammetric method was applied to determine LOP in its pure form, pharmaceutical formulation, in presence of coadministered drugs omeprazole, trimebutine, and naproxen and in human plasma. In the applied method, a newly fabricated carbon paste electrode chemically modified with silver sulfadiazine and zinc oxide was used. Experimental parameters such as pH of Britton-Robinson buffer, scan rate and applied current potential of the electrode surface were optimized. The morphological structure of the newly fabricated electrode was illustrated using transmission electron microscopy. Using Britton Robinson buffer of pH 8.00, LOP showed an irreversible anodic peak of 0.827 V. The manufactured sensor displayed high sensitivity and optimum charge/electrode kinetic transmission. Linear calibration curve was obtained between the peak current and the corresponding concentration of LOP over the range (14.00 × 10-12- 1.00 × 10-4M) with low detection limit of about (4.00 × 10-12M) indicating good sensitivity. The proposed method was validated according to the ICH guidelines. The proposed sensor was also applied to determine LOP in human plasma after successfully validating the method according to the FDA bioanalytical methods guidelines. The greenness of the method was assessed using the Analytical Eco-Scale approach and the results reveal that the developed method is not only greener and uses non-hazardous chemicals than the previously reported HPLC methods for LOP determination in biological fluid but also can be used in the quality control laboratories for LOP determination in pharmaceutical formulation and in human plasma. © 2022 Electrochemical Society Inc.. All rights reserved.