Integration of a derivatization protocol and LC–MS sequential window acquisition of all theoretical mass spectra strategy for amino acid determination in human plasma

Amino acids (AAs) comprise fundamental components of the human organism since they participate in several physiological functions. Numerous methods have been developed to quantify AAs in biological fluids due to the challenges posed by matrix handling (limited sample quantities, complexity) and their physicochemical properties (protein binding, low detectability, and high polarity). This study developed and validated an LC–MS method using ion‐pairing chromatography, a sequential window acquisition of all theoretical mass spectra approach and a derivatization kit for AA analysis of physiological fluids to simultaneously quantify plasma AAs and provide data for untargeted analytical approaches. Finally, proof of concept was demonstrated through the analysis of 450 samples from a dietary intervention study with protein‐enriched wheat biscuits.