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 β-lactam antibiotics [Ag(β-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 × 10^–4–1 × 10^–2 mol/L; the limit of detection is 2.5 × 10^–5–8.9 × 10^–5 mol/L for unmodified, 5.6 × 10^–6–7.5 × 10^–5 mol/L for modified, and 4.2 × 10^–5–7.2 × 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.