A hydrazone-selective electrode based on the vanillin hydrazone - tetraphenylborate ion pair in a poly(vinyl chloride) matrix membrane is proposed for the determination of vanillin. Vanillin was first reacted with Girard's reagent P [1-(carbazoylmethyl)pyridinium chloride] to give the corresponding hydrazone in aqueous solution. The hydrazone was generated in situ and was then determined with the vanillin hydrazone-selective electrode. The electrode exhibits significant potentiometric response in the concentration range 10-2 -4 × 10-5 M hydrazone. It has a working pH range of 4.5-6, a short static response time (less than 60 s) and the response remains stable for at least 1 month. The results obtained with the proposed method agreed well with those given by UV spectrophotometry. This methodology could be extended to carbonyl compounds.
