Amoxycillinium‐Selective plastic membrane electrodes based on amoxycillinium‐phosphotungstate ion associate

The (1:3) (phosphotungstate:amoxycillinum) ion associate is used as the ion exchanger in preparing conventional and coated wire plastic‐membrane electrodes for amoxycillin (Am). The performance characteristics of the electrode are as follows: presoak time, 30 minutes; average slope: 59 ± 0.8 mV/ concentration decade, at 25°C, for 24 hours of continuous soaking; usable concentrations range, 1.96 × 10 −4 to 1.5 × 10 −2 M (Am); working pH range 3 to 9, and mean isothermal coefficient, 2.25 × 10 −3 mV/°C. The electrode displays very good selectivity for Am toward a large number of inorganic and organic cations. The standard addition method and potentiometric titration are used to determine Am in pure solutions and in pharmaceutical preparations.