Determination of free amino acids in infant food by capillary zone electrophoresis with mass spectrometric detection.

A method for the quantitative determination of free amino acids in infant food samples using capillary electrophoresis (CE) with electrospray-mass spectrometric (ESI-MS) detection is presented. According to the zwitterionic nature of the analytes, two different modes of separation as well as detection were tested; highly acidic carrier electrolytes combined with MS detection in the positive ion mode proved to be the optimum solution. Sensitivity as well as linearity of the method were sufficient to allow the analysis of all solutes of interest in a single run. In this way, free amino acids could be analyzed in a variety of infant food preparations without any sample pretreatment or derivatization step.