A highly selective and sensitive colorimetric chemosensor based on polyurethane foam impregnated with 3-methyl-2, 6-dimercapto-1,4-thiopyrone for on-site preconcentration and determination of palladium(ll)

摘要

A new sorbent and chemosensor for highly selective and sensitive on-site preconcentration and colorimetric determination of Pd(II) was developed based on its reaction with 3-methyl-2,6-dimercapto-1,4-thiopyrone (MDT) immobilised onto polyurethane foam (PUF). Complexation of Pd(II) with MDT sorbed on PUF tablets leads to a contrast change in the sorbent colour from pale yellow to reddish-brown. The developed chemosensor is highly selective with respect to the transition and platinum group metals. It has a maximum sorption capacity of 17 mu mol g(-1) for Pd(II). Reaction is possible in a strongly acidic medium (up to10 M HCl), and the properties of the chemosensor do not change during storage for a long time. The colorimetric response of the chemosensor was measured using red-green-blue (RGB) colour model. The dependence of the luminosity of the G channel on the Pd(II) concentration was linear in the concentration range from 0.3 to 64 mu g L-1 with a detection limit of 0.1 mu g L-1 (R-2 = 0.997). The colour scale for visual detection of Pd(II) was constructed in the concentration range of 0.02-0.64 mg L-1 for the sorption from 20 mL of an aqueous sample. The accuracy of the developed methods was assessed by the analysis of a certified reference material (platinum-palladium alloy) and by comparison with the results of gravimetric or graphite furnace atomic absorption spectrometry (GFAAS) determination of Pd. The developed method was successfully applied to determine Pd in samples of mine water and road dust, in the electrolyte bath and in the sewage sludge of a palladium electroplating bath.