Effect of Different Cuvettes on Detection of Acidity of Water by Near Infrared Spectroscopy and Correction Analysis

In order to reduce the effect of different cuvettes on the measurement results of near infrared spectroscopy, as well as improve the prediction accuracy of quantitative analysis model for the acidity of water, the removel effect of orthogonal signal correction (OSC) on the spectral background interference from different curvettes was discussed. Two cuvettes from the same batch were used to load 32 water samples with different pH values, and near infrared spectral data were collected, and OSC was used to preprocess the original spectra. The difference between the two groups of spectra before and after OSC preprocessing was compared, and the partial least squares (PLS) quantitative analysis models were established to analyze the effect of spectral difference on the prediction accuracy of the models. As shown by the results, after OSC preprocessing, the average difference value between the two groups of spectra decreased from 0.004 2 to 0.001 3, and the spectral correction rate reached 90%. Compared with the PLS models established by the original spectra, the prediction accuracy of the PLS models established by the spectra after the OSC preprocessing was significantly improved, and the difference values of predicted root-mean-square error decreased from 0.912 to 0.205, and that of correlation coefficient decreased from 0.364 to 7.00×10^-3, and both of them reduced by 78% and 98%, respectively.