Diffuse reflection spectroscopy of indium sorbates with immobilized heterocyclic azo compounds

Diffuse reflection has been used for the direct determination of indium after preconcentration on a solid support. The best conditions were found for sorption of indium complexes with 1 -(2-pyridplazo)-2-naphthol (PAN), 4-(2-pyridylazo)resorcinol (PAR) and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) Immobilized on a silica gel Silochrom S-120. Optical characteristics of the complexes in solutions and on sorbent are practically the same for the variations of the Gurevich-Kubelka-Munk function, color lightness and chromaticity coordinates. The linear solutions of variations of these quantities with the indium contents were determined. It was demonstrated that 4 mu g indium could be concentrated on 0.3 g modified silica gel with immobilized 5-Br-PADAP from a sample volume of 200 ml with an enrichment factor exceeding 600. (C) 1998 Elsevier Science B.V.