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.