When Liquid Chromatography is used for purity test, it is generally performed by comparing the peak area of target impurity from the sample solution with that of the main component from a standard solution,which is prepared by diluting the sample solution to a concentration corresponding to the specified limit of the impurity,or by calculating target impurity content using the peak area percentage method. Unless otherwise specified,if a sample is separated into isomers in the chromatogram, the isomer ratio is calculated by using the peak area percentage method.