Ion-paired RP-HPLC for determining fermentation end products of Streptococcus mutans grown under different conditions

Abstract

A rapid, specifi c and reliable ion-paired high performance liquid chromatographic assay of small organic acids in bacterial cultures was developed. The assay was conducted using a mixture of 6.0 x 10 -3 mM tetrabutylammonium phosphate and 5 % v/v acetonitrile in water as the mobile phase. Calibration curves for acetic, lactic, and pyruvic acid were linear within the concentration ranges determined (r 2 > 0.9990). Selective removal of interfering compounds from bacterial cultures improved the reliability of the method, demonstrating that more than 90% of the tested acids were recovered. Replicate regression analyses of acid standard plots obtained on three different days gave correlation coeffi cients of r 2 > 0.9995. The assay was precise within a day and between days as indicated by an ANOVA test. According to the validation results and from the analysis of the cultured samples, the described method may be adequate for the routine determination of acid metabolites of lactic acid bacteria.