A chronoamperometric method to estimate ionophore loss from ion-selective electrode membranes

A novel chronoamperometric method was developed to estimate the concentrati on of a neutral ionophore in fixed-site, dioctyl sebacate plasticized, poly (vinyl chloride)based, ion-selective electrode membranes. The membranes con tained between 0.5 and 16 mmol/kg valinomycin. The chronoamperometric techn ique was used to estimate the valinomycin concentration in freshly prepared membranes and after extraction of some of the ionophore from the membranes using dioctyl sebacate. Replicate measurements indicated a relative standa rd deviation in the calculated valinomycin concentration of less than 10%, and these values accurately represented the true concentration of valinomyc in within 10%, The method permitted an estimate of the valinomycin concentr ation after valinomycin was leached from a membrane. The results of prelimi nary experiments using heparinized dog blood suggest that blood protein ads orption does not interfere qualitatively or quantitatively with the analysi s.