Applicability of Near Infrared Spectrum Model

In order to well maintain near infrared spectrum model,15 sealed inactivated tobacco samples and microcrystalline cellulose samples sealed in 3 bottles were separately detected by 3 NIR instruments of different types.Variance analysis and differential spectrum analysis were used to investigate the effects of sample bottle,alteration of light source in instrument and testing time on spectra of the same sample.Furthermore,the samples were qualitatively analyzed by the discriminant model based on Principal Component Analysis(PCA) and Mahalanobis distance.The results showed that sample bottles of identical and homogeneous material and light source alteration hardly affected the spectra of sample and the prediction accuracy of model,while the spectra of the same sample detected by the same instrument changed to a certain extent with the lapse of time and the prediction accuracy of the model also decreased gradually.It means that the mathematical model has a limited service life,once the prediction accuracy is lower than the specified threshold,it has to be replaced by a new model or the spectra of newly detected sample has to be corrected.