甲酯化气相色谱法检测化妆品中防腐剂十一烯酸及其锌盐

采用硫酸催化甲酯化法检测了化妆品中的十一烯酸及其锌盐,并对甲酯化试剂、硫酸浓度、反应体系含水量、甲酯化温度、反应时间等条件进行了优化,发现反应体系的含水量对产率影响较明显。以5%硫酸甲醇溶液为甲酯化试剂,65℃水浴中反应1 h,正己烷为提取溶剂,采用GC/FID色谱法测定,外标法定量。十一烯酸甲酯产率达95%以上,该方法在0.05～1.0 mg范围内线性良好(r>0.999),检出限和定量下限分别为0.001 2%和0.004%。膏霜、乳液、化妆水和洗手液中十一烯酸的平均回收率为93%～104%,相对标准偏差为0.39%～5.1%。

Determination of Undecylenic Acid and Zinc Undecylenate in Cosmetics by Methyl Esterification-GC/FID Method

A sulfuric acid catalyzed esterification method was chosen for the determination of undecylenic acid(UA) and zinc undecylenate(ZnUA) in cosmetics.Effects of different operation parameters such as methyl esterification reagent,sulfuric acid concentration,water content in reaction system,reaction temperature and time were investigated.The result indicated that water content in reaction system had a great impact on esterification reaction.Under the optimal conditions,heated in 65 ℃water bath for an hour,UA and ZnUA were esterified with 5% sulfuric acid-methanol using n-hexane as extraction solvent.Methyl undecenoate was analyzed by GC with hydrogen ion flame detector(FID) and quantified by the external standard method.The yield of methyl undecenoate was calculated to be above 95%.The method had a good linearity in the range of 0.05-1.0 mg with correlation coefficient more than 0.999.The limit of detection(LOD) and the limit of quantitation(LOQ) of undecylenic acid were 0.001 2% and 0.004%,respectively.The average recoveries of UA in cream,lotion,toner and sanitizer were between 93% and 104% with relative standard deviations(RSDs) of 0.39%-5.1%.