Determination of organic acids in fermentation products of milk with high performance liquid chromatography/on-lined micro-dialysis

A micro-dialysis technique connected on-line to an HPLC with acidic water a s eluent was examined to develop an environmental-friendly analytical metho d for determining organic acids in fermentation products of milk After bein g diluted and adjusting the pH, organic acids in the sample were diffused t hrough a cellular dialysis membrane into the perfusion stream (water) under the controlled conditions. The optimum conditions for obtaining efficient dialysis of organic acids such as perfusion flow-rate, pH and addition of s alt to the sample solution, as well as chromatographic conditions were inve stigated. The organic acids, citric, lactic, acetic, and formic can be well separated on a C18 column only eluted with water at pH 2.9 and 0.6 mL min( -1) flow-rate. The proposed method provided a very simple "green" procedure to determine organic acids in complicated matrices. Application was illust rated by the analysis of citric acid, lactic acid, acetic acid, and formic acid in two fermentation products.