This work presents synthesis, and characterization of a novel [diresorcinate‐1,10‐phenanthrolinecobalt(II)] (DHRPCo) complex, and potentiodynamic fabrication of poly(DHRPCo)/GCE for SWV determination of procaine penicillin G (ProPenG) in various pharmaceutical and biological samples. While UV‐Vis and FT‐IR results demonstrated stepwise synthesis of DHRPCo, the CV and EIS results evidenced modification of the surface of GCE by an electroactive polymer film that improved electrode surface area. In contrast to the peak of ProPenG at the unmodified electrode, an irreversible oxidative peak at poly(DHRPCo)/GCE with lower potential and six folds of current enhancement observed, that confirmed electrocatalytic effect of the polymer, SWV response of poly(DHRPCo)/GCE showed linear dependence on concentration of ProPenG in the range 0.1–200 μM, with LoD of 4.9 nM. Spike recovery results in various pharmaceutical and biological samples in the range 98.03–106.50 %, interference recovery in the presence of selected potential interferents at their various levels with associated errors under 3.39 %, and stability of the modifier with analysis time validated the method for determination of ProPenG. Poly(DHRPCo)/GCE was applied for determination of ProPenG in three brands of injection pharmaceutical formulation, human urine, human blood serum, and cow's milk samples. While no ProPenG was detected in the human urine, serum, and cow's milk samples, detected ProPenG in the injection powder samples was within 96.1–101.3 % of company label. The developed method showed superior performance over recently reported methods making it an excellent candidate for determination of ProPenG in real samples.

This study covers the development of a fast, selective, sensitive, and stable method for the simultaneous determination of cephalosporins (cephalexin (CLN) and cefadroxil (CFL)) in biological fluids and tablet samples using potentiodynamic fabrication of a poly(resorcinol)-modified glassy carbon electrode (poly(reso)/GCE). The results of cyclic voltammetry and electrochemical impedance spectroscopy supported the modification of the GCE by a polymer layer that raised the electrode surface area and conductivity. At the poly(reso)/GCE, an irreversible oxidative peak with four- and fivefold current enhancement for CLN and CFL, respectively, at a substantially lower potential demonstrated the catalytic action of the modifier. Under optimized solution and parameters, the peak current response at the poly(reso)/GCE revealed a linear dependence on the concentration of CLN and CFL within the range 0.1-300 and 0.5-300 μM, respectively, with a limit of detection (LoD) of 3.12 and 8.7 nM, respectively. The levels of CLN in four selected tablet brands and CFL in two tablet brands were in the vicinity of 91.00-103.65% and 97.7-98.83%, respectively, of their nominal values. The recovery results for CLN in pharmaceutical samples were in the range of 99.00-100.67% and for CFL 97.9-99.75% and for blood serum and urine samples 99.55-100.55% and 99.33-100.34% for CLN and 97.13-100.60% and 96.73-102.50% for CFL, respectively. Interference recovery results with errors less than 4.81%, lower LoD, wider dynamic range, excellent recovery results, and good stability of the modifier compared to those for the previously reported methods validated the use of the poly(reso)/GCE for determining CLN and CFL simultaneously in various real samples.

A one step facile synthesis of the novel diaquabis(1,10-phenanthroline)copper(II)chloride (A₂P₂CuC) complex is demonstrated. Cyclic voltammetric and electrochemical impedance spectroscopic results revealed potentiodynamic deposition of a conductive electroactive poly(A₂P₂CuC) film on the glassy carbon electrode surface increasing its effective surface area. In contrast to the unmodified glassy carbon electrode, appearance of an oxidative peak at a reduced potential with over two fold current for amoxicillin at poly(A₂P₂CuC)/GCE demonstrated its electrocatalytic property attributed to reduce charge transfer resistance and the improved surface area of the electrode surface. Better correlation of the oxidative peak current with square root of scan rate (R² = 0.99779) than with scan rate (R² = 0.96953) supplemented by slope of 0.58 for log(current) versus log(scan rate) confirmed diffusion controlled irreversible oxidation of amoxicillin. At optimized solution and SWV parameters, current response of poly(A₂P₂CuC)/GCE showed linear dependence on concentration of amoxicillin (2.0–100.0 μM) with LoD 0.0115 μM. While no amoxicillin was detected in the human blood serum sample, an amount 89.40–100.55% of the nominal level was detected in the analyzed eight tablet brands. Spike recovery in tablet samples (98.90–101.95%) and blood serum sample (102.20–101.37%); interference with an error (%RSD) of 0.00–4.51% in tablet and 0.00–2.10% in serum samples; excellent stability and reproducible results, added with the wide dynamic range and low LoD validated the method for amoxicillin determination in pharmaceutical formulations and human urine samples.