Solid Phase Extraction and Spectrophotometric Determination of Palladium Using 2-Methyl-5-(4-carboxylphenylazo)-8-hydroxyquinoline as a Chromogenic Reagent

Abstract

Synthesis and application of 2-methyl-5-(4-carboxylphenylazo)-8-hydroxyquinoline (MCPAHQ) as a new chromogenic reagent for the determination of palladium has been described. Highly sensitive, selective and fast method for determination of palladium based on its rapid reaction with MCPAHQ and solid phase extraction of the coloured chelate on the CLEAN-UP^® C₁₂ cartridge has been developed. In the presence of pH 3.2 citric acid-sodium citrate buffer solution and emulsifier-OP medium, MCPAHQ reacted with palladium to form coloured chelate of palladium-to-MCPAHQ molar ratio of 1:2. This chelate was enriched by the solid phase extraction with a reversed phase C₁₂ cartridge. The enrichment factor of 50 was obtained by elution of the chelates from the cartridge with minimal amount of ethanol. In ethanol medium, the molar absorptivity of the chelate was 2.15 × 10⁵ L mol^-1 cm^-1 at 510 nm. Beer's law is obeyed in the range of 0.01-0.6 μg/mL. The relative standard deviation for eleven replicate sample of 0.8 μg/ L level was 2.2 %. In the orginal sample detection limit was 0.1 μg/L. The proposed method was applied to the determination of trace palladium in automobile exhaust gas converter catalysts with good results.