A New Study of Calibration Model Transfer Method for Near-Infrared Spectral Analysis

Although, near-infrared (NIR) has been successfully applied to rapid and non-destructive analysis in various fields, however the problem that calibration model developed on one instrument can't be directly applied to other instruments in many cases has not been solved yet. To achieve calibration model transfer between different types of instruments (master instrument: SupNIR-2700, slave instrument: Nicolet Antaris) and the model transfer between the spectra of different resolutions measured on one instrument (Nicolet Antaris II), an improved calibration model transfer method is proposed in this work, being referred as SP-SG1st-PDS method. In terms of the proposed method, firstly, a fitting slave spectrum is constructed with cubic spline interpolation without destroying the information on the original slave spectrum. Then, Savitaky-Golay (first order derivative) smoothing is applied to remove the baseline drift between the master and slave spectra. Finally, PDS is applied to the model transfer to remove most of the differences between the master and slave spectra. SP-SG1st-PDS method has been applied to predict the content of vinyl acetate (VAC) in ethylene-vinyl acetate copolymer (EVA). Comparative studies of the proposed model transfer technique, the wavelet de-noising method (SP-WT-PDS) and the S-G smoothing method (SP-SG-PDS) have also been accomplished. As for the model transfer between different types of instrument, comparative experiment results have shown that the root mean-square error of prediction (RMSEP) with the proposed SP-SGUt-PDS method reduced from 15.978 2 to 0.239 0 and much smaller than that with SP-SG-PDSmethod (0.549 0) and that with SP-WT-PDS method (0.528 8). Meanwhile, the bias of prediction was improved obviously after the model transfer with the proposed method. For the model transfer between the spectra at different resolutions measured on one instrument, the comparative experiment results have shown that the model prediction accuracy can be improved significantly, accompanied by the reduction in RMSEP from 0.475 1 to 0.194 5. With the proposed SP-SG1st-PDS method, the calibration model transfer can be applied to different types of instruments and different resolutions of spectra measured on the same instrument.