Laser thermal lens spectrometric determination of trace palladium with 2-(3,5-dichlor-pyridylazo)-5-dimethylaminoaniline

A method for the determination of trace palladium based on the colour reaction between 2-(3,5-dichlor-pyridylazo)-5-dimethylaminoaniline (3, 5-diCl-PADMA) and palladium by laser thermal lens spectrometry was proposed. The experimental results show that in strong acidic medium, such as 0.02 - 1.6 mol/L H₂SO₄, 0.02 - 1.3 mol/L HCl and 1.6 - 4.8 mol/L HClO₄, and in the presence of acetone, palladium can react with 3,5-diCl-PADMA to form a stable complex exhibiting an absorption maximum at 623 nm. Based on these characteristics, the title method was developed. The sensitivity of this method was about 10 times higher than that of conventional spectrophotometric method. The detection limit and linear range of palladium(II) are 0.002 mg/L and 0.005 - 0.25 mg/L respectively. It has been applied to the determination of palladium in alloy and catalyst samples with satisfactory results.