Multiorigination of chromatographic peaks in derivatized GC/MS metabolomics: a confounder that influences metabolic pathway interpretation.

GC/MS is one of the most commonly used analytical methods in metabolomic research. The originations of chromatographic peaks are crucial, especially for metabolic pathway interpretation. However, until now, this critical issue has not been discussed or investigated. This study aims to demonstrate one of the major pitfalls of derivatized GC/MS and their possible implications in metabolomic studies. In this investigation, a spectrum of structural and biological related endogenous species including phosphocholines (PC), lysophosphatidylcholines (LPC), diacylglycerol (DAG) and fatty acids were used as examples to illustrate the multiorigination and multipeak phenomena of derivatized GC/MS. The implications of these phenomena on metabolic pathway interpretations were also discussed. Our findings revealed that peaks of glycerol, phosphoric acid, fatty acids and some lipids fractions in derivatized GC/MS chromatogram of human blood were the result of contributions of structurally related compounds, in both free and conjugated form. It is believed that these phenomena could have been due to decomposition occurred during derivatization procedure and/or during GC analysis where the temperatures of certain GC parts were too high. To avoid misleading results and wrong conclusions in metabolomic investigations, combined use of GC/MS with other analytical instruments, such as NMR and/or LC/MS, should be considered.