白酒中乳酸的离子排斥色谱-直接电导检测分析

Determination of Lactic Acid in Chinese Liquors by Ion-exclusion Chromatography with Direct Conductivity Detection

建立用直接电导检测的离子排斥色谱分离测定乳酸的方法。以Shim-pack SCR-102H色谱柱为分离柱,用对p-甲苯磺酸为流动相,考察流动相浓度、色谱柱温度及流速对分离和测定乳酸的影响。最佳色谱条件为以2.0mmol/L p-甲苯磺酸为流动相、流速1.0mL/min、柱温50℃。在此条件下,乳酸的保留时间约为8min,其他有机酸(甲酸、乙酸、柠檬酸和苹果酸)不干扰测定。乳酸的检出限为0.36mg/L,工作曲线的线性范围是1.0～100.0mg/L,峰面积的相对标准偏差(n=5)为0.9%。将方法应用于测定白酒中的乳酸,加标回收率为95.8%～98.5%。

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）.