Application of three chromogenic reagents to the determination of palladium using a laboratory-made optical fibre detector for flow-injection analysis

Abstract

Palladium in ore was determined by a method in which an optical fibre detector is connected to a flow-injection analysis system and using three chromogenic reagents, i.e., 1,8-dihydroxy-2-(4-chloro-2-phosphonophenylazo)-7-(6,8-disulphonaphthylazo)naphthalene (RI), 1,8-dihydroxy-2-(4-chloro-2-phosphonophenylazo)-7-(4-sulphonamidophenyl-azo)-3,6-disulphonaphthalene (RII) and 1,8-dihydroxy-2-(4-chloro-2-phosphonophenylazo)-7( p-hippuric acid azo)-3,6-disulphonaphtalane (RIII). The methods are simple, rapid and selective. In the PdRI system, the molar absorptivity is 4.3 × 10 4 1 mol −1 cm −1 at 650 nm and Beer's law is obeyed in the range 13 μg Pd ml −1. In the PdRII system, the molar absorptivity is 3.0 × 10 4 1 mol −1 cm −1 at 640 nm and Beer's law is obeyed in the range 1–4 μg Pd ml −1. In the PdRIII system, the molar absorptivity is 3.4 × 10 4 l mol −1 cm −1 at 639 nm and Beer's law is obeyed in the range is 1–5 μg Pd ml −1. Coexisting noble metal ions do not interfere. An optical fibre detection cell for flow-injection analysis and an optical fibrespectrophtometer were designed and constructed in-house.