Aim: Vanillin used as a positive control substrate of aldehyde oxidase activity gets metabolized to vanillic acid. Low MW and low sensitivity in negative ion mode are challenges with these analytes. Our objective was to develop a simple offline derivatization LC-MS/MS method to address these challenges.
Methodology/results: A simple dansyl chloride derivatization of the phenolic groups on vanillin and vanillic acid was adopted to enable easy ionization in commonly used acidic mobile phases. Calibration curves were linear over the concentrations of 4.88-1250 nM with an LLOQ of 0.64 fmoles on column for both analytes.
Conclusion: The qualified method was successfully applied to simultaneously measure vanillin and vanillic acid in plasma and urine from a guinea pig pharmacokinetic study.
Keywords: aldehyde oxidase; derivatization; guinea pig plasma; pharmacokinetics; tandem mass spectrometry; vanillic acid; vanillin.