Method for directly determining enantiomer excess of chiral compound in mixed sample

The invention discloses a method for directly determining an enantiomer excess of a chiral compound in a mixed sample. The method comprises the following steps: separating the chiral compound with the enantiomer excess to be determined from other impurities by virtue of a first-dimension chromatographic unit, and collecting a chiral enantiomer into a quantitative loop; by switching two ten-way valves, transferring the chiral enantiomer which is collected into the quantitative loop into a second-dimension chromatographic unit which is provided with a chiral chromatographic column; and determining the enantiomer excess of the chiral compound in the quantitative loop through the second-dimension chromatographic unit. According to the method, the enantiomer excess of the chiral compound in the mixed sample can be directly determined without need of an early-stage complicated sample purification process, so that the production cost is greatly reduced, and the analysis time is shortened; meanwhile, the separating capacity of a chromatographic system is improved. The method is wide in application range, and is particularly suitable for determining the enantiomer excess of a chiral drug in an asymmetric synthesis crude product.