An implementation of the PLS (partial least-squares) statistical approach to quantitative analysis was applied to a set of mid-infrared spectra obtained from a series of commercial detergent samples. The components analyzed included the base detergent, sodium benzoate, 2-propanol, 1,2-propanediol, polypropylene glycol, and glycerol. The samples were analyzed with the use of a horizontal attenuated total reflectance (ATR) accessory equipped with a zinc selenide crystal. The PLS model created in the calibration was found to provide excellent results for a set of validation samples.
M. P. Fuller, G. L. Ritter, and C. S. Draper, "Partial Least-Squares Quantitative Analysis of Infrared Spectroscopic Data. Part II: Application to Detergent Analysis," Appl. Spectrosc. 42, 228-236 (1988)