Determination of Deuterated D- and L-Aromatic Amino Acids by GC-MS and Prior Clean-up of Plasma

Abstract

Deuterium-labeled compounds may be used as tracers in human metabolic studies. In this investigation, GC-MS-SIM analysis of D and L-Phe-d₅, d₃, Tyr-d₄, d₇ and Trp-d₅ was performed. With the exception of Trp-d₅ determination as its TMS derivative, the above deuterium-labeled amino acids were determined as their TFA-Me, TMS and BDMS derivatives. The fragmentions used for GC-MS-SIM are marked with a star in Fig. 1. No unfavorable elimination of deuterium was observed during derivatization (Fig. 2). This method was used for plasma samples after appropriate prior clean-up using cation-exchange (SCX) and non-polar (C₁₈) minicolumns. Optical isomer separation was performed by HPLC using an enantio-selective column, CROWNPAK CR (+), which contains a chiral crown ether as a chiral selector (Fig. 3).