AMOXYCILLINIUM-SELECTIVE PLASTIC MEMBRANE ELECTRODES BASED ON AMOXYCILLINIUM-PHOSPHOTUNGSTATE ION ASSOCIATE

The (1:3) (phosphotungstate:amoxycillinium) ion associate is used as t he ion exchanger in preparing conventional and coated mire plastic-mem brane electrodes for amoxycillin (Am). The performance characteristics of the electrode are as follows: presoak time, 30 minutes; average sl ope: 59 +/- 0.8 mV/ concentration decade, at 25 degrees C, for 24 hour s of continuous soaking; usable concentrations range, 1.96 x 10(-4) to 1.5 x 10(-2) M (Am); working pH range 3 to 9, and mean isothermal coe fficient, 2.25 x 10(-3) mV/degrees C. The electrode displays very good selectivity for Am toward a large number of inorganic and organic cat ions. The standard addition method and potentiometric titration are us ed to determine Am in pure solutions and in pharmaceutical preparation s.