Isolation and derivatization of plasma taurine for stable isotope analysis by gas chromatography-mass spectrometry

Abstract

A method for the isolation and derivatization of plasma taurine is described that allows stable isotope determinations of taurine to be made by gas chromatography-mass spectrometry (gc-ms). The isolation procedure can be applied to 0.1 ml of plasma: the recovery of plasma taurine was 70–80%. For gc separation, taurine was converted to its dimethylaminomethylene methyl ester derivative which could not be detected by hydrogen flame ionization, but could be monitored readily by NH 3 chemical ionization mass spectrometry. The derivatization reaction occurred partially on-column and required optimization of injection conditions. Using stable isotope ratiometry multiple ion detection, [M + 2 + H] + [M + H] + ion ratio of natural abundance taurine was determined with a standard deviation of less than ±0.07% of the ratio. The [1,2- 13C]taurine/taurine mole ratios of standard mixtures could be accurately determined to 0.001. This stable isotope gc-ms method is suitable for studying the plasma kinetics of [1,2- 13C]taurine in infants who are at risk with respect to taurine depletion.