Analysis of underivatized amino acids: zwitterionic hydrophilic interaction chromatography combined with triple quadrupole tandem mass spectrometry.

Analysis of underivatized amino acids is challenging regarding both separation and detection of this small, polar, and largely UV-inactive compounds. Additives for reversed phase chromatography such as ion-pairing reagents can hamper mass spectrometric detection. Zwitterionic hydrophilic interaction chromatography using MS compatible eluents together with tandem mass spectrometry in multiple reaction monitoring mode for selective detection is an attractive approach to overcome the above mentioned issues.