Electroanalytical Properties of Unmodified and Modified Solid-Contact Potentiometric β-Lactam Sensors in Aqueous and Biological Media

A comparative study of the electroanalytical properties of solid-contact sensors (tubular, planar) in solutions of cefuroxime (Cefur), cefotaxime (Ceftx), cefixime (Cefix), and amoxicillin (Amox) is performed. Associates of tetraalkylammonium-tetradecylammonium (TDA) and dimethyldistearylammonium (DMDSA)-with complex compounds of silver(I) and beta-lactam antibiotics [Ag(beta-lac)(2)]TAA and modifiers such as ZnO, polyaniline, and polyaniline nanotubes are used as electrode-active components (EACs). The sensors under study based on [Ag(Cefur)(2)]TDA and [Ag(Amox)(2)]DMDSA are characterized by a short response time in solutions of cefotaxime, cefuroxime, cefixime, and amoxicillin: 20-25 and 12-17 s for tubular unmodified and modified, respectively; 20-25 and 10-15 s for planar unmodified and modified, respectively. The linear range of electrode functions in solutions of antibiotics is 1 x 10(-4)-1 x 10(-2) mol/L; the limit of detection is 2.5 x 10(-5)-8.9 x 10(-5) mol/L for unmodified, 5.6 x 10(-6)-7.5 x 10(-5) mol/L for modified, and 4.2 x 10(-5)-7.2 x 10(-5) mol/L for planar sensors. The potential drift is 8-12 mV/day for unmodified and 5-7 mV/day for modified planar sensors; the service life is 1.5-2 months. An advantage of planar sensors is their use in microassay detection, which is relevant in the analysis of biological media. Application of solid-contact sensors for determination of the antibiotics under study in model aqueous solutions, medicinal products, and oral fluid in the case of various infectious diseases is demonstrated.