Direct Determination of Plasma Free Amino Acids by Combined MRM-SIM Method on LC/MS/MS

Introduction

Unbound or free amino acids in human blood and urine are important metabolites, which are either ingested or synthesized endogenously in human body. The levels and profiles of the so-called plasma free amino acids are determined clinically for diagnosis of specific diseases and researches of cancer biomarker discovery. Analyses of amino acids by HPLC and LC- MS methods are well-established unavoidably with pre-column derivatization to improve chromatographic separation and detection sensitivity. A direct LC/MS/MS analysis method for amino acids without derivatization is adopted in this study, which could be achieved essentially due to use of a combined mode column. We described here a method and performance of quantification of twenty free amino acids in human plasma and serum using a combined MRM-SIM mode on triple quadrupole LC/MS/MS. The purpose of incorporating SIM mode in the method is to enhance the detection sensitivity of a few very small amino acids like glycine, which MRM transition is rather poor leading to low sensitivity.

September 16, 2016 GMT