Modified solid-contact sensors for determination of cefuroxime and cefalexin in medicines and oral fluid

Abstract

Cefuroxime, cefuroxime axetil and cefalexin are broad-spectrum pluripotential cephalosporin antibiotics. Their determination in various objects suggests using expensive spectroscopic, chromatographic, electrochemical equipment and organic solvents. Potentiometric sensors can provide rapid detection of cephalosporin antibiotics in a small sample volume without a preliminary sample preparation. The study is aimed at the developing of modified solid-contact potentiometric sensors for determination of cefuroxime and cefalexin in aqueous, biological media, and pharmaceuticals. The electroanalytical characteristics of unmodified and modified polyaniline and copper oxide nanoparticle sensors are evaluated. Tetradecylammonium(TDA) with a silver (I) – cefuroxime complex are used as the active membrane components, whereas polyaniline and copper oxide nanoparticles are used as modifiers. The main electroanalytic and operational characteristics of the studied sensors in aqueous solutions of antibiotics and against the background of oral fluid (LRP) are determined. The results of comparative evaluation of the electroanalytical properties of unmodified and modified solid-contact sensors in aqueous media of some â-lactam antibiotics and against the background of oral fluid are presented. The sensors based on Ag (Cefur)2TDA are characterized by a short response time: for modified polyaniline (PAN) and copper oxide nanoparticles within 5 – 10 sec, for unmodified — 10 – 20 sec. The linear range of the electrode functions for unmodified and modified sensors is 1 × 10–4 – 1 × 10–1 M, the detection limit is 7.4 × 10–5 M for unmodified and 6.3 × 10–5 M for modified sensors, respectively. The potential drift is 6 – 12 and 4 – 6 mV/day, service life is 1.5 and 2 months for unmodified and modified sensors, respectively. The modifiers stabilize the electrode potential, perform the function of the electron transfer mediator thus enhancing the electroanalytical characteristics of the sensors. The effect of the redox agents on the sensor properties is revealed: 1 × 10–3 – 1 × 10–4 MK 2Cr2O7 and FeCl3 solutions reduce the linearity intervals of the electrode functions, KI and Mohr’s salt do not affect the characteristics of the sensors in cefuroxime and cephalexin solutions. The coefficients of potentiometric selectivity of cefuroxime-selective sensors (modified with CuO nanoparticles) with respect to cefazolin, cefotaxime, and cefalexin are close to unity; Kijpot with respect to inorganic anions being part of the oral fluid (, Cl Br,I,HCO3 ,H PO 24 ,HPO4 2) are n × 10–2 – n × 10–3. This indicates the possibility of using sensors for detecting individual cephalosporin antibiotics or their total content in the presence of 100 – 1000 fold excesses of inorganic ions in medicinal and biological environments, small sample volumes, which is important when studying the pharmacokinetics of antibiotics and in determination of the maximum therapeutic dose when adjusting the treatment process.