Stability of amino acids and related amines in human serum under different preprocessing and pre-storage conditions based on iTRAQ®-LC-MS/MS

Amino acids analysis or metabonomics requires abundant serum/plasma samples collection and samples storage has become inevitable given the limited capacity for immediate analysis. Currently, most of the existing studies on metabolites stability during sample storage focused on long-term and short-term stability, while many functional amino acids might be ignored due to the poor sensitivity and detection of analysis methods. Here, we attempted to elucidate the stability of amino acids and related amines as comprehensive as possible in human serum following different preprocessing and pre-storage procedures. Pooled, fasting serum samples were collected and stored at 4 °C and 22 °C respectively after a delay in sample processing (0, 1, 2, 4, 8, 12 and 24 hours) and underwent freeze-thaw cycles for three times at −80 °C. The concentration of amino acids and related amines were quantified using isobaric tagging reagent iTRAQ®-LC-MS/MS. Approximately 54.84 %, 58.06 % and 48.39 % of detectable and target analytes altered at 4 °C and 22 °C during pre-treatment and freeze-thaw cycles. Some amino acids which are not stable and relatively stable were found. Our study provided detailed profiles and suggestions for amino acids in human serum corresponding to diverse collection and pre-treatment measures.