Discrimination of Patchoulis of different geographical origins with two-dimensional IR correlation spectroscopy and wavelet transform

Patchouli is a common used traditional Chinese herbal medicine for flatulence or vomit with a long history in China and some other Asian countries. Patchoulis of different geographical origins usually have different curative effects. In order to evaluate their qualities, it's very necessary to discriminate them. Our objective of this study is to develop a nondestructive and accurate identification method. The results in this paper showed that it's difficult to use conventional infrared spectra and second derivative spectra directly to distinguish them. But it's quite easy to use two-dimensional infrared (2D IR) correlation spectra, especially after applying wavelet transform process, to discriminate them. The resolution of the 2D IR spectrum is improved obviously after wavelet transform process, more peaks appear and the peaks become quite clear and separate. The differences of the 2D IR spectra become rather remarkable. In this way, it's not difficult to discriminate the patchoulis of different geographical origins. This will be a nondestructive, economical and rapid way to distinguish complicated mixture like traditional Chinese medicines. Combined 2D IR and wavelet transform, Fourier transform infrared spectroscopy would become more powerful in analysis and discrimination.