Quantitative Analysis Of Methanol In Methanol Gasoline Based On NIR Spectroscopy Combined With Calibration Transfer Technology

Methanol gasoline is an important part of new green fuel.Methanol content plays an extremely important role in the quality evaluation of methanol gasoline.Therefore,the quick and accurate quantitative analysis of methanol in methanol gasoline is particularly important.Near infrared(NIR)spectroscopy is one of the effective tools to detect methanol gasoline because of its unique advantages of simple,rapid and non-destructive analysis.However,due to the change of NIR instrument types and experimental conditions,the multivariate calibration model established by one NIR instrument can not be shared with other instruments,which seriously restricts the accurate quantitative or qualitative analysis of NIR spectroscopy,and has become one of the key research directions in the field of NIR spectroscopy.This study takes methanol gasoline as the research object.Aiming at the key problems of quick and accurate analysis of methanol content in methanol gasoline and the applicability of NIR spectroscopy analysis model,this study carries out research on quick and accurate quantitative analysis of methanol in methanol gasoline based on NIR spectroscopy and chemometrics methods,and the NIR spectroscopy calibration transfer method based on piecewise direct standardization(PDS),kernel domain adaptive-partial least squares(KDA-PLS)and 1st derivative-variable selection-model updating(D1st-VS-MU)was studied.Finally,a quantitative analysis method of methanol in methanol gasoline based on calibration transfer technology combined with partial least squares(PLS)was established.This research can provide a new idea and method for quick and accurate detection of methanol content in methanol gasoline and quality evaluation.The main research contents of this paper are as follows:(1)Taking methanol gasoline as the research object,an analytical method for quick and accurate quantitative analysis of methanol in methanol gasoline based on NIR spectroscopy combined with the WT-PDS-PLS,was established by PDS calibration transfer strategy with standard sample.The NIR spectra of methanol gasoline samples were collected by two different types of NIR instruments,and the influence of four different spectral pretreatment methods on the analysis ability of PLS calibration model were explored;The WT-PLScalibration model was established based on the NIR data of methanol gasoline processed by wavelet transform(WT);Furthermore,the WT-PDS-PLS calibration model was established based on the PDS calibration transfer method.The results show that compared with the WT-PLS calibration model,the WT-PDS-PLS calibration model performs good analytical ability(R2P=0.9993,RMSEP=0.3586%,and MREP=2.69%).Therefore,NIR spectroscopy combined with the WT-PDS-PLS is an effective analysis method for the detection of methanol content in methanol gasoline,which can effectively improve the applicability of NIR spectroscopy analysis model of methanol gasoline.(2)In order to further improve the practical application of calibration transfer of methanol gasoline NIR spectroscopy,an analytical method for quick and accurate quantitative analysis of methanol in methanol gasoline based on NIR spectroscopy combined with the WT-VIP-KDA-PLS,was established by KDA-PLS calibration transfer strategy without standard sample.The influence of variable importance in projection(VIP)on the analysis ability of PLS calibration model was explored;Then the WT-VIP-PLS calibration model established on the master was transferred to the slave by KDA-PLS calibration transfer method,and the WT-VIP-KDA-PLS calibration model was established.The results show that the WT-VIP-KDA-PLS calibration model has excellent analytical ability(R2P=0.9990,RMSEP=0.3334% and MREP=1.78%).It shows that compared with the WT-PDS-PLS calibration model with standard sample,the WT-VIP-KDA-PLS calibration model without standard sample has the advantages of good analysis ability and strong practical application.(3)The D1st-VS-MU calibration transfer strategy was proposed to further improve the applicability of NIR spectroscopy analysis model of methanol gasoline,and an analytical method based on NIR spectroscopy combined with the WT-D1st-VS-MU-PLS was established,which can realize the quick and accurate quantitative analysis of methanol in methanol gasoline.The D1st-VS method was used to extract the spectral variables with small differences between different instruments,and the model updating(MU)was performed based on the D1st-VS.Finally,based on the D1st-VS-MU calibration transfer strategy,the WT-D1st-VS-MU-PLS calibration model was established.The results show that the WT-D1st-VS-MU-PLS calibration model has excellent analytical ability(R2P=0.9995,RMSEP=0.3028%,MREP=2.81%),which is equivalent to the prediction results of the slavere-modeling.It further improves the applicability of NIR spectroscopy analysis model of methanol gasoline.