Salicylate-selective electrodes based on Al(III) and Sn(IV) salophens

New salicylate-selective electrodes based on aluminum(III) and tin(IV) salo phens are described. The electrodes were prepared by incorporating the iono phores into plasticized poly(vinyl chloride) (PVC) membranes, which were di rectly coated on the surface of graphite electrodes. These novel electrodes display high selectivity for salicylate with respect to many common inorga nic and organic anions. The influence of membrane composition and pH and th e effect of lipophilic cationic and anionic additives on the response prope rties of the electrodes were investigated. The electrode based on aluminum salophen, with 32% PVC, 65.8% plasticizer, and 2.2% ionophore, shows the be st potentiometric response characteristics and displays a Linear log [Sal(- )] vs EMF response over the concentration range 1 x 10(-6)-1 x 10(-1) M in phosphate buffer solutions of pH 7.0, with a Nernstian slope of -59.2 mV/de cade of salicylate concentration. Highest selectivity was observed for the membrane incorporating 38.8% PVC, 57.3% plasticizer, 2.6% Sn(salophen), and 1.3% sodium tetraphenylborate. The electrodes exhibit fast response times and micromolar detection limits (similar to 1 x 10(-6) M salicylate) and co uld be used over a wide pH range of 3-8, Applications of the electrodes for determination of salicylate in pharmaceutical preparations and biological samples are reported.