Application Research Of NIRS In Quality Control Of Calamine And Its Products

Objective:To establish crude,counterfeit and calcined calamine identification model by near infrared principal component analysis and cluster analysis.To establish the determination of Zinc Oxide content of calamine model using NIRS Based on MIV and BP-ANN algorithm.To establish a fast determination model of zinc oxide content in calcined calamine by NIRS based on PLS algorithm,and to explore methods through judging the end point of calamine calcination.To realize the quality control of calamine,calcined calamine and online monitoring of calamine calcination process.Methods:?1?To collect near infrared spectroscopy of crude,counterfeit and calcined calamine samples.Each category sample was randomly divided into training set and testing set.To screen the preprocessing method and the characteristic spectrum to establish the principal component discriminant analysis model and the cluster analysis model respectively.?2?To collect near-infrared spectra of samples,and preprocess these spectra with first derivative.The ZnO content in each sample were determined by ethylene diamine tetraacetic acid?EDTA?titration and taken as reference value of NIRS.Samples were categorized into calibration and prediction set using the Kennard-Stone?K-S?algorithm.First,in the calibration set,according to the square correlation coefficient?r²?-wave number???figure to obtain the characteristic spectral bands.Then,to obtain the optimal characteristic spectral bands by the mean impact value?MIV?algorithm.And then,both internal cross and external validation were used to screen the number of hidden layer nodes of BP-ANN.Finally,to get the BP-ANN model of determination of ZnO content.?3?Eight batches of calamine samples sourced from hydrozincite with different sizes and textures were calcined at different temperatures.During the calcination process,ZnO contents,XRD patterns and near-infrared spectra of the samples were used to analysis their changes rules.The model of determining ZnO content of calcined calamine was established to use near-infrared spectroscopy based on partial least squares regression?PLS?algorithm.In addition,this paper summarized the change rules of calamine in calcination according to XRD patterns,using the"K value"quantitative method to define the characteristic T value.When the T value was equal to1.00?100%?,that is to say,the calamine sample was completely calcined.Then,to establish the T value analysis model using PLS algorithm.Results:?1?Spectrum were preprocessed by the first derivative.The characteristic spectrum of the principal component discriminant analysis model was 4 800-4 000 cm^-1,and the characteristic spectrum of the cluster analysis model was 7 300-7 000,4 800-4 000 cm^-1.In the principal component discriminant analysis model,the prediction accuracy rate was 94.34%.In the cluster analysis model,the prediction accuracy rate was 96.23%.?2?The model analyzed ZnO content in Calamine samples ranging within42.05⁶9.98%,with RMSECV of 1.66%and coefficient of determination?R²?of 95.75%in internal cross and RMSEP of 1.98%,R² of 97.94%and ratio of performance to deviation?RPD?of 6.11 in external validation.?3?The determination model of ZnO content in calcined calamine can analyze ZnO content ranging within 41.13-93.43%.In terms of the internal cross validation of training set,the RMSECV was 2.81%.In the predicted results of validation set,the RMSEV was 3.09%,the R² was 94.93%and the RPD was4.52.In the predicted results of test set,the RMSEP was 1.89%,the R² was97.75%and the RPD was 6.44.The model of predicting T value was excellent with RMSECV of 0.0721%,R² of 96.01%and RPD of 5.01 in internal cross-validation and RMSEP of 0.0829%,R² of 94.95%and RPD of 4.64 in external validation.Because the model's prediction accuracy for T values was not exactly 100%,taking into account some errors in the experimental analysis process,this study stipulated when the T value was 1.00±5%,it could be judged that the calamine was completely calcined.Conclusion:Through internal cross-validation and external verification,the established models have good effects and strong predictive ability.It realized the rapid identification of crude,counterfeit and calcined calamine,the rapid determination of zinc oxide content of crude calamine,the rapid determination of zinc oxide content of calcined calamine,and the rapid judgment of the calcination degree of calcined calamine.They provided convenient,fast and environmentally friendly methods for the quality control of calamine and calcined calamine,and also provided new methods for on-line monitoring of calamine calcination process.