Analysis of chloroformate-derivatised amino acids, dipeptides and polyamines by LC-MS/MS

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed which, with sample preparation using a commercially available kit, allows rapid quantitation of 39 chloroformate-derivatised amino acids (AAs), polyamines (PAs) and dipeptides (DPs) in complex biological matrices. Lower limits of quantitation (LOQ) were 20-150 nM for putrescine, spermine, spermidine, cadaverine, agmatine, and below 5 μM for all analytes. Responses were linear for all analytes between 0.5 and 50 μM. Quantitative measurements of all 39 metabolites were achieved within a 15 min runtime. The method was evaluated with a Pseudomonas aeruginosa cell extract study (n = 24) and a larger human urine study (n = 308). Batch effects were observed in the urine study and an investigation of instrument and sample stability showed a wave-like pattern in the MS responses. Both the run order and inter-batch variation were successfully corrected by normalising to pooled urine quality control data. Thus, this method should be suitable for diverse biological matrices and for large as well as small sample sets.