Creager, et. al., described a simple method for construction of a salicylate ion selective electrode. Polyvinylchloride is codissolved with tetraoctylammonium salicylate in tetrahydrofuran in a standard 15 mL beaker. After the solvent is allowed to evaporate, the membrane was removed with forceps and 1 cm diameter disks were cut out of it with a cork borer. Using open-top caps, the PVC membrane disks were sealed onto electrode bodies made from 3 dram vials with the bottoms removed. The electrode body was filled with aqueous 0.1 M NaCl / 0.1 M Na-salicylate and capped with a rubber septum with a Ag/AgCl electrode inserted through it. A standard Ag/AgCl reference electrode completed the cell. Although simple in design and construction, the electrode yielded a detection limit as low as 10-4 M salicylate. However, benzoate was found to exhibit a relatively significant interference, with a fSalicilate/benzoate of 3 x 10-3.
Creager, S.E., Lawrence, K.D., Tibbets, C.R., J. Chem. Ed., 72, 1995, 274-276.