LIGNOCAINE ION-SELECTIVE ELECTRODES BASED ON ITS ION-ASSOCIATES WITH COBALT THIOCYANATE, PHOSPHOMOLYBDATE AND REINECKATE COMPLEX-IONS

Lignocaine (Lg) selective PVC membrane electrodes based on the ion-ass ociates lignocaine-cobalt thiocyanate (I), lignocaine-phosphomolybdate (II) and lignocaine-reineckate (II) were constructed. The electrodes exhibited linear response over the concentration ranges 0.02-100, 0.01 -100 and 0.01-100 mM for I, II and III, respectively. pH did not affec t the electrodes performance within the ranges 3-6, 3-7 and 3-6.5 for 10(-2), 10(-3) and 10(-4) M LgHCl, respectively. Interferences are neg ligible for many inorganic cations, sugars and amino acids. The isothe rmal coefficients were found to be 0.000459, 0.000698 and 0.000404 V d egrees C-1 for I, II and III, respectively. The life spans of the elec trodes are more than 2 months of continuous work. Potentiometric titra tion and the standard addition method were used to determine LgHCl in pure solutions and in pharmaceutical preparations with high accuracy a nd precision.