Optical and Chromaticity Characteristics of Adsorbates of the Thorium Complex of Arsenazo I

The immobilized reagent Arsenazo I was used for the direct determination of trace thorium by diffuse reflectance spectrometry and chromaticity measurements. Silica gels Silochrom C-120 and C₁₈ were studied as supports. The optimal conditions of sorption were found. The dependence of chromaticity functions (chromaticity coordinates, color lightness, saturation, yellowness, and whiteness) on different chemical factors was studied. The advantages of the use of yellowness, color hue, and total color difference in comparison with other chromaticity functions was demonstrated. A method was developed for the determination of thorium with a detection limit of 0.02 g/mL.