抄録
The infrared spectro-photometry is a method to measure the degree of infrared radiation (IR) absorbed in the material to identify a chemical compound. Identification is made by comparing the spectrum of a sample with the spectrum of a standard substance having an expected structure. To improve the objectivity of judgment, Mahalanobis distance was used by comparing the degree of correspondence between the sample and the standard. For testing, a compound having polymorphism which belongs to a group of compounds having the same structure but different physical property such as solubility was selected. This type of sample is hard to discriminate by IR spectra. From the normal crystal, approximately 200 IR spectra were measured. The absorption rate of each wave number in a spectrum was considered as the characteristic to be used for the construction of Mahalanobis space. After the comparison of the Mahalanobis distances between normal and abnormal crystals,it was proven that the discriminating power was excellent, although there existed the multi-collinearity problem. This problem was lessened by eliminating the highly correlated peaks and reselecting the characteristics. Mahalanobis distance approach is an effective method in quantifying the degree of correspondence of infrared spectra, also in discriminating different substances.
