Isotachophoretic Determination of Amino Acids After Their Conversion to Hydroxy Acids

Abstract

Determination of amino acids by capillary isotachophoresis is presented. Developed method is suitable for separation of amino acids from relatively simple mixtures, especially for dietary supplements. The most of amino acids is not possible to separate directly by isotachophoresis. Thus, they had to be converted to other compounds. Chemical conversion to corresponding hydroxy acids in presence of nitrite acid was used. This necessary nitrite acid was prepared by reaction of sodium nitrite with acetic acid. Under optimization, concentration 0.1 mol/L sodium nitrite and acetic acid was found. As the best electrolyte system for separation of hydroxy acids, 0.01 mol/L HCl, 0.05% hydroxyethyl cellulose, with β-alanine (leading electrolyte of pH=3.6) and 0.01 mol/L valeric acid with sodiumhydroxide (terminating electrolyte of pH=7.24) were chosen.