Application of near infrared spectroscopy in fast assay of liquid components in single-base propellant intermediates

The liquid components (including water and residual solvent (RS)) content is an important quality indicator of single-base propellant intermediates. This work presented a quick method for the determination of water and RS content in single-base propellant intermediates employing near infrared (NIR) spectroscopy in place of costly, laborious and time-consuming reference analysis (gas chromatography, GC). The Monte-Carlo uninformative variable elimination (MCUVE) and the backward interval partial least squares (Bi-PLS) were applied for characteristic variable selection during the modeling process. In this case, Bi-PLS algorithm showed the superiority when compared with MCUVE method for multivariate calibration due to sample intrinsic inhomogeneity. The correlation coefficient of the calibration and prediction (Rc, Rp), and the root mean square error of calibration and prediction (RMSEC, RMSEP) of the obtained optimum models by Bi-PLS algorithm were 0.98, 0.99, 0.28%, 0.36% for water, and 0.99, 0.99, 0.34%, 0.42% for RS, respectively. No significant difference existed between the reference and NIR method according to the result of a paired t-test. In addition, the repeatability of the NIR method met the requirement of the reference method. The results indicated that the NIR method built in this work would have a bright prospect in rapid measurement of liquid components content single-base propellant intermediates.