Development and validation of LC-MS/MS method for amino acid analysis and its practical application in mouse serum with ulcerative colitis

The quantification and analysis of free amino acids (FAAs) in serum is important for illness diagnosis due to its content varies with the body's condition. In this study, a new sensitive analytical method based on liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS/MS) was optimized for simple and rapid simultaneous detection of 20 amino acids by pre-column derivatization. Amino acid derivatized by 9-fluorenyl methyl chloroformate (FMOC-Cl) were eluted and separated by simple mobile phase reagent in 20 min via gradient elution using a traditional reverse phase C18 column (150 x 4.6 mm, 5 mu m), at the flow rate of 0.8 mL/ min. After optimizing derivatization, LC-MS/MS conditions, and sample pre-treatment, this method was verified with LODs and LOQs ranging from 0.0237 to 0.2391 ng/mL and 0.079 to 0.7971 ng/mL. The intra- and inter-day precision was no more than 10 %. The overall accuracy and recovery varied from 88.4-111 % and 88.7-114 %, respectively. Those methods were first applied to mice serum with ulcerative colitis. The results showed that the levels of Ala, Arg, Trp, Lys, Cys, Tyr, and Phe significantly increased in pre-treated group by egg white peptides, which will participate in metabolism. This study provides a valuable reference for further research on the pathogenesis of ulcerous colitis and the development of functional foods to relieve inflammation and balance metabolism.