Amino acid analysis via LC-MS method after derivatization with quaternary phosphonium.

(5-N-Succinimidoxy-5-oxopentyl)triphenylphosphonium bromide (SPTPP) is a highly sensitive and positively charged precolumn derivatization reagent for the analysis of amino acids in liquid chromatography-electrospray ionization-tandem mass spectrometry. The synthesis of this reagent and handling of the derivatization reaction are quite simple. It reacts with amino acids rapidly and with high efficiency. MS/MS analysis revealed that the SPTPP-derivatized amino acids formed strong product ions; thus, highly sensitive and selective detection is possible in the selected reaction monitoring mode. The limits of detection for the SPTPP-derivatized amino acids are in the sub-fmol range. The sensitivities of the derivatized amino acids increased about 500-fold, as compared to those of underivatized amino acids.