Quality control of liquid laundry detergents by NIR spectroscopy

Liquid laundry detergents contain fabric softeners, bleaching agents, surfactants, and enzymes. Of these, the surfactant is the most important contributor for the cleaning effect, as it breaks down the interface between polar and nonpolar compounds. This allows detergents to be effective cleaning agents against grease and stains. Surfactant content together with viscosity, pH value, and dry matter are important quality control parameters in detergent formulations. Measurement of these parameters is usually performed by time-consuming primary analysis methods (e.g., two-phase potentiometric titration for surfactants), often requiring different techniques. Near-infrared spectroscopy (NIRS) is a fast, chemical-free alternative for use atline or in a quality control lab.

This Application Note shows the feasibility of using near-infrared spectroscopy for the analysis of dry matter, pH value, viscosity, and surfactant content in liquid detergent. These quality control parameters can be measured simultaneously in seconds without any chemicals or sample preparation.

NIRS saves laundry detergent manufacturers time and money as it can be used in several steps of the production chain or during quality control of the final product. Additionally, only one technology is required with NIRS, compared to the other standard analytical techniques often used for these determinations (Table 1).