Development of a rapid and direct method for the determination of organic acids in peach fruit using LC-ESI-MS.

An accurate, simple and rapid liquid chromatography mass spectrometry method for the determination of organic acids in peach fruit has been developed. Direct injection and sample clean-up with a mixed-mode sorbent was compared. The best results for the determination of gluconic, oxalic, malic, citric and fumaric acids were obtained with only a simple dilution and filtration step, and nylon filters should be avoided since some organic acids are retained by them. It is the first time that gluconic acid has been determined in peach fruit. Different parameters involved in the separation and detection process have been optimized. Since matrix effects were observed in the peach commodity, organic acids were quantified by the standard addition method. All validation parameters of the method were found acceptable of all organic acids. Finally, the method was successfully applied to the analysis of samples of peach from two cultivars.