MPSS: A New Scattering Technique for Sensitive Measuring of the Total Absorption of Fluids

Abstract

Optical methods are appropriate tools to detect organic micro-pollutants in fluids. A simple technique is introduced which uses radiation scattered elastically by the fluid. Two different signals are measured: (1) the linear or conventional scattering (CS), which occurs at short pathlengths of the incidence radiation in the fluid, and (2) the multipath-saturation scattering (MPSS) originating at long pathlengths, e.g., in multipath-reflection cuvettes, where the radiation is fully absorbed by the fluid. A relation between the scattering signals and the total absorption coefficient of the fluid is theoretically derived. A simple experiment is performed that takes into consideration the scattering of distilled water polluted with azobenzene and quinine-sulfate. A xenon lamp and a nitrogen laser are used to generate CS and MPSS. The scattering ratio CS/MPSS yields the total absorption directly. In comparison to the conventional absorption technique, CS/MPSS is characterized by a higher sensitivity.