Abstract: Fourier transform infrared(FTIR) spectroscopy equipped with horizontal attenuated total reflection(ATR) accessory was applied to the multicomponent quantitative analysis in organic phase. Anovel method was developed to directly determine the Hainanmycin(HNMS, an insoluble antibiotic from the fermentation) in water and ethyl alcohol solution. Calibration models were established on the basis of partial least squares with infrared spectra(IR) and secondderivative absorbance spectra(DIR) of the standard mixtures. The better predicted results is obtained especially at lower concentration of HNMS by DIR method. The standard errors of prediction of HNMS by IRor DIRare 0.18 and 0.19 g/L, respctively. The standard errors of prediction of water and alcohol are 0.0011 volume ratio by either quantitative method. The method is rapid and convenient without any pretreatment.

Key words: Fourier transform infrared spectroscopy, Attenuated total reflection, Partial least squares, Quantitative analysis, Organic phase