Partial least squares method is a multivariate statistical method. For spectral analysis of multi-component mixed systems, it can make full use of the absorbance and concentration information in calibration samples, and can also perform quantitative measurement when there is matrix interference [10-11]. Therefore, partial least squares was used to simultaneously quantify the content of many different types of plasticizers in PVC plastic samples.
First, determine the infrared spectra of each reference standard, establish a library of reference standards, and then use TQAnalystv6 quantitative analysis software to establish an analytical method to determine the spectral bands used for quantitative analysis. There are three spectral bands that can be used for quantitative analysis. They were: 2965.98-1425.11, 1421.28-1033.66, 1031.73-908.31cm-1. Finally, the reference standard sample was measured by partial least squares method. The results are shown in Table 1. The correlation coefficients were 0.99124 (DEHP), 0.99996 (TCP), 0.99900 (DEHA), and 0.99607 (ATBC).
Table 1
2.4 Precision Experiments To examine the precision of the method, the samples to be tested were prepared according to the recipes in Table 2, and the infrared spectra at different points of the same sample were directly collected using a single-reflection ATR-OMNI sampler, in the TQAna-lystv6 quantitative analysis software. The spectrum was called to directly obtain the plasticizer content at different points in the sample. The results are shown in Table 2. The results in Table 2 show that the precision of this method is very good, and its RSD is less than 6%.
