Discrimination of Organic Solvents Using an Infrared-Emitting Diode-Based Analyzer. Part I: Feasibility

Abstract

This report demonstrates the feasibility of discriminating organic solvents on the basis of short-wave near-infrared spectra (from 0.7 to 1.1 μm). Both library searching and multivariate statistical methods were applied to 8-cm⁻¹ spectra and to spectra de-resolved to the point achievable with an analyzer using discrete infrared-emitting diode sources. Library searching performed satisfactorily if the unknown and library spectra were collected under reasonably similar conditions, but performed poorly if the temperature of hydrogen-bonding solvents was varied. A multivariate discrimination technique based on Mahalanobis distance computation was capable of discriminating between several alcohols while allowing for a temperature variation of 20°C. These results indicate that a very low resolution (on the order of 100 cm⁻¹) short-wave near-infrared analyzer can achieve successful discrimination between similar solvents under variable conditions.