Determination of Organic Acids in Alfalfa Silage by Capillary Isotachophoresis and Capillary Zone Electrophoresis

Abstract

Analysis of acetic, lactic, propionic, and butyric acids in silages using both capillary zone electrophoresis (CZE) with conductivity detection and capillary isotachophoresis (CITP) is described. A linear detector response was found in the concentration range 50-500 and 40-120 µmol.l^-1 for CZE and CITP, respectively. The limit of detection (3S/N) as found by CZE and CITP was 3 and 2 µmol.l^-1, respectively, and the limit of quantification (10S/N) 10 and 5 µmol.l^-1, respectively. Based on the analysis of 10 silage samples, the accuracy of both methods was compared using the calculated regression equation: c_CZE = (1.22 ± 0.05).c_CITP - (0.6 ± 0.5), r = 0.962. CZE afforded a higher concentration of lactic acid than CITP (P 0.05) while no significant difference was observed for the determination of all other acids. The developed CZE method separates all acids in less than 7 min and thus it could become preferred for the routine examination of changes in lactic acid concentration.