LASER THERMAL LENS SPECTROMETRIC DETERMINATION OF RHODIUM BY THE NEW CHROMOGENIC REAGENT 5-BROMO-(2THIAZOLYLAZO)-5-DIETHYLAMINOBENZOIC ACID

A highly sensitive method for determination of rhodium by laser thermal lens spectrometry based on the colour reaction between rhodium and the new chromogenic reagent 5-bromo(2-thiazolylazo)-5-diethylaminobenzoic acid (5-Br-TADEB) has been developed. The experimental results show that in a acetic acid-sodium acetate buffer solution of pH 4.0–5.7 and in the presence of acetone, rhodium reacts with 5-Br-TADEB to form a 1 : 2 stable blue complex exhibiting an absorption maximum at 632 nm which is well-matched to the wavelength of the laser beam used (? = 632.8 nm). The detection limit and linear range of rhodium(III) are 0.004 µg mL-1 and 0.01–0.08 µg mL-1, respectively. The method has also been applied to determine rhodium in catalyst samples with satisfactory results.