Figure 18-Ex02Creager, 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.