NEW ION-SELECTIVE ELECTRODES FOR DETERMINATION OF BUPIVACAINE AND OXYBUPROCAINE

PVC membrane electrodes selective for hydrochlorides of the anaesthetics bupivacaine (BpC) and oxybuprocaine (ObC) are prepared. The electrodes have a near Nernstian slope (58 mV for BpC and 51 mV for ObC electrodes) over the range of 1.6 x 10(-5)-10(-1)M and 1.3 x 10(-1)M for BpC and ObC electrodes, respectively. The change in pH of the test solution within the ranges 2.5-6.0 and 3.0-7.4 does not affect the EpC-and ObC-electrodes, respectively. The electrodes have very long life times (10 days for BpC, and 3 months for ObC) and exhibit good selectivity for the investigated compounds with respect to a large number of inorganic cations and organic substances of biological importance. The isothermal coefficients of the electrodes are calculated from the standard electrode potentials at different temperatures. BpC and ObC are determined successfully in some pharmaceutical preparations using the calibration graph technique and potentiometric titration.