Synthesis and evaluation of a diethylammonio-propylsulfate amphoteric ionic column for the high-performance liquid chromatography-mass spectrometric separation and detection of amino acids.

A diethylammonio-propylsulfate amphoteric ionic resin was synthesized and employed as the stationary phase for high-performance liquid chromatography-mass spectrometry (LC-MS) separation and detection of amino acids. The influence of experimental conditions such as mobile phase composition, column length and temperature upon the amino acid separations was evaluated. However, temperature, addition of water-miscible organic solvent to the mobile phase and mobile phase gradients were not effective at improving the separations. In contrast, the use of an unbuffered pure water mobile phase proved successful for the separation and detection of amino acids. The observed order of elution seems to parallel the isoelectric points of the respective amino acids and suggests that this diethylammonio-propylsulfate stationary phase column functions as an amphoteric ion-exchanger. Under optimized chromatographic conditions, the detection limits for the amino acids were in range of 0.07-0.44 pmol (pico-mole). The method was also successfully applied for the analysis of an actual commercial sample.