Quantitative determination of CL-20 polymorphs by mid-infrared diffuse reflectance spectroscopy

The quantitative calibration models of three polymorphs α-CL-20, γ-CL-20, ε-CL-20 in ε-CL-20 product were established by mid-infrared diffuse reflectance spectroscopy combined with partial least squares (PLS) method of chemometrics, and the cross-validation and external validation to the models were performed. Results show that three models have high accuracy and precision, the determination coefficients of cross-validation (R²) are 0.9973, 0.9714, 0.9848, respectively, and the root mean square error of cross-validation (RMSECV) are 0.222%, 0.650%, 0.670%, respectively. In the external validation, the root mean square error of prediction (RMSEP) are 0.422%, 0.813%, 1.02%, respectively, and the paired t-test results show that there is no significant difference between predicted values and actual ones. The quantitative analysis method of CL-20 polymorphs based on the above models can be applied to the product quality test of ε-CL-20, and the studies on the polymorph stability of ε-CL-20 in technical process and long-time storage of explosives and propellants.