Rapid Determination of Nitrate in Chinese Cabbage Using Fourier Transforms Mid-infrared Spectroscopy

The nitrate content in Chinese cabbage was rapidly predicted using the techniques of mid-infrared spectroscopy (diffusion reflectance spectroscopy, photoacoustic spectroscopy and attenuated total reflectance spectroscopy). There existed interferences in the characteristic bands of nitrate (1200–1500 cm−1) for all the infrared spectra. The interferences for diffusion reflectance spectra were strongest, followed by photoacoustic spectra, and the weakest for the attenuated total reflectance spectra, which were also verified by the principal component regressions between infrared spectra and nitrate content in Chinese cabbage, and the coefficient (R2) were 0.4003, 0.4874 and 0.8741, respectively. Based on attenuated total reflectance spectra, the chemometrics method of partial least squares was involved to improve the prediction model of nitrate, the prediction accuracy was significantly decreased, the coefficient was 0.8851, and the RPD value was 3.19. Therefore, the technique of mid-infrared attenuated total reflectance spectroscopy was feasible for rapid monitoring of nitrate in Chinese cabbage.

The determination of nitrate in Chinese cabbage by FTIR-ATR was strongly interfered by water absorption due to large moisture content in fresh samples. However, in the wavenumber region of 1200–1500 cm−1, the determination was less influenced, and the nitrate showed main contribution to the absorption band and can be used to qualify nitrate content combining chemometrics method.Figure optionsDownload as PowerPoint slide