Elucidation of O-phosphoryl and N-phosphoryl amino acids by electrospray ionization tandem mass spectrometry

Mass spectroscopic characteristics of phosphoryl amino acids were studied in detail by positive and negative electrospray ionization mass spectrometry (ESI‐MS) in conjunction with tandem mass spectrometry (MS/MS). Besides N‐diisopropyloxyphosphoryl amino acids (N‐DIPP‐AA), O‐phospho‐ and O‐diisopropyloxyphosphoryl amino acids (O‐DIPP‐AA) were studied and compared to N‐DIPP‐AA. The fragmentation pathways of [M+H]+, [M+Na]+ and [M−H]− ions of phosphoryl amino acids were summarized. In addition to several similar patterns. each of them showed its characteristic fragmention.