[Analysis and identification of Geranium by two-dimensional correlation infrared spectroscopy].

Tri-step infrared spectroscopy (Fourier transform infrared spectroscopy (FTIR) combined with second derivative spectra and two-dimensional correlation infrared spectroscopy (2D-COS)) was employed to identify and analyze the main components of Heilongjiang (HLJG), Jilin (JLG), Liaoning (LNG) genuine Herba Geranium. The emergence of several characteristic absorption peaks of tannins including 1 730 and 1 337 cm(-1) and peaks around 1 618 and 1 318 cm(-1) belonging to calcium oxalate suggested that Herba Geranii contained tannins and calcium oxalate. Differences near 1 370 and 1 230 cm(-1) were found among the three Herba Geranii. In light of second derivative spectra, four more peaks of tannin components around 1 509, 1 204, 764 and 763 cm(-1) and evident differences around C=O stretching bands (1 750-1 600 cm(-1)) were observed. By 2D-COS spectra with further improved resolution, the three genuine Geraniums were visually distinguished due to their significant differences in auto-peak profile. HLJG has 7 auto peaks with a strongest peak around 1 621 cm(-1), while JLG and LNG both have only 4 auto peaks with a strongest peak around 1 580 and 1 659 cm(-1), respectively. It was demonstrated that the Tri-step infrared spectroscopy was successfully applied to fast analyze and identify genuine Geraniums from different geographical regions and subsequently would be applicable to the study of Chinese medicinal resources and quality standards.