[Investigation on baseline correction in pollutant monitoring on-line by NIR spectroscopy]

Spectroscopic data pre-processing is important to spectra scaling and quantitative analysis, and correction of baseline drift caused by variation of measuring condition is critical in NIR spectroscopy analysis in-situ. In the present paper, the NIR absorption spectra of propane and isobutane with different concentration were detected by BRUKER EQUINOX55 spectrometer. The "Derivative-smooth" method and the baseline correction method which is accessory of the instrument were theoretically analyzed, and the data processed by the two kinds of method were compared. The results show that the method that is accessory of the instrument can correct steady-state and linear drift, and can gain high SNR, high accuracy; "Derivative-smooth" method has better applicability, can correct non-steady-state and nonlinear drift better, and is a good kinds of pre-processing method in analysis in situ.