Potentiometric Method for Determining Biologically Non-Degradable Antimicrobial Substances

Ion selective electrodes (ISEs) based on polymer plasticized membranes have been developed for the determination of benzalkonium chloride (alkyldimethylbenzylammonium), the active component being cesium bis-octodecyl-2-sulfonio- closo -decaborate Cs[B 10 H 9 S(C 18 H 37 ) 2 ] (sensor A). For the determination of norfloxacin hydrochloride, the active component is potassium tris-octodecyl-1-ammonio- closo -decaborate K[B 10 H 9 N(C 18 H 37 ) 3 ] (sensor B). It has been shown that the electrodes have a reversible potentiometric response with respect to the analyzed cations in the presence of a number of other inorganic and organic cations. The influence of the concentration of the electrode-active substance on the electrochemical characteristics of the manufactured sensor has been studied. The optimal composition of the ion-sensitive membrane has been found. It has been determined that the developed sensors provide a wide range of detectable concentrations (for sensor A, 2 × 10 –7 –1 × 10 –2 ; for sensor B, 1 × 10 –7 –1 × 10 –2 ) and a low detection limit (for sensor A, 1 × 10 –7 M; for sensor B, 8 × 10 –8 M). New ISEs can be recommended for direct potentiometric detection of free ions in water bodies and water extracts of soils.