Ki K R, Lee J, Ha D, Kim J H
College of Pharmacy, Sungkyunkwan University, Suwon, South Korea.
J Chromatogr A. 2000 Sep 8;891(2):257-66. doi: 10.1016/s0021-9673(00)00690-7.
The simultaneous enantiomeric separation of 30 racemic acids including 24 hydroxy acids in a single analysis is described for the determination of their absolute configurations. It involves the conversion of each enantiomer into diastereomeric O-trifluoroacetylated (-)-menthyl ester for the direct separation by gas chromatography on achiral dual-capillary columns of different polarities, with subsequent identification and chiral discrimination by retention index (I) library matching. Among the acids studied, the enantiomers of 27 acids were discriminatively resolved on both non-polar DB-5 and the intermediate-polar DB-17 columns with resolution factors in the range of 0.7-7.7 and separation factors in the range of 1.002-1.021. Enantiomers of 3-hydroxybutyric and alpha-methoxyphenylacetic acids were partially resolved on DB-5 (resolution factor of 0.9), but not resolved on DB-17, while the baseline resolution for 3-hydroxydecanoic acid and the minimal separation on the peak top (resolution factor less than 0.7) for 2-hydroxyglutaric acid were achieved on DB-17 but not on DB-5. The temperature-programmed I values measured on both columns were characteristic of each enantiomer and thus simple I matching with the reference values was useful in cross-checking for their chemical identification and the chiral discrimination as well. When applied to a clinical urine sample, the present method allowed positive identification of endogenous (S)-lactic acid and (S)-2-hydroxybutyric acid along with (R)-3-hydroxybutyric acid.
本文描述了在一次分析中对30种外消旋酸（包括24种羟基酸）进行同时对映体分离，以确定其绝对构型。该方法包括将每种对映体转化为非对映体的O-三氟乙酰化(-)-薄荷酯，通过气相色谱在不同极性的非手性双毛细管柱上进行直接分离，随后通过保留指数（I）库匹配进行鉴定和手性鉴别。在所研究的酸中，27种酸的对映体在非极性的DB-5柱和中等极性的DB-17柱上都得到了鉴别性分离，分离度因子在0.7-7.7范围内，分离因子在1.002-1.021范围内。3-羟基丁酸和α-甲氧基苯乙酸的对映体在DB-5柱上部分分离（分离度因子为0.9），但在DB-17柱上未分离，而3-羟基癸酸在DB-17柱上实现了基线分离，2-羟基戊二酸在DB-17柱上在峰顶部实现了最小分离（分离度因子小于0.7），在DB-5柱上未实现。在两根柱上测得的程序升温I值是每种对映体的特征，因此简单的I值与参考值匹配对于交叉核对其化学鉴定和手性鉴别也很有用。当应用于临床尿液样本时，本方法能够阳性鉴定内源性(S)-乳酸、(S)-2-羟基丁酸以及(R)-3-羟基丁酸。
