Abstract: An ion-exclusion chromatographic method for the determination of lactic acid was developed using direct conductivity detection. Chromatographic separation was performed on a Shim-pack SCR-102H column using p-toluenesulfonic acid as eluent. The effects of eluent concentration, column temperature and flow rate on the retention time of lactic acid were investigated. The optimized chromatographic conditions for determining lactic acid were using 2.0 mmol/L p-toluenesulfonic acid as the eluent, column temperature 50 ℃ and flow rate 1.0 mL/min. The resulting retention time of lactic acid was about 8 min. Common organic acids (formic acid, acetic acid, citric acid and malic acid) did not interfere with the determination. The detection limit (RSN = 3) for lactic acid was 0.36 mg/L. The calibration curve of the method was linear in the range of 1.0－100.0 mg/L. The relative standard deviation for five replicate determinations of chromatographic peak area was 0.9%. The average spike recoveries of lactic acid from five brands of Chinese liquors ranged from 95.8% to 98.5% (n = 5).

Key words: lactic acid, ion-exclusion chromatography, conductivity detection, Chinese liquors