The determination of lead and cadmium in paint by atomic-absorption spectrophotometry utilising the Delves micro-sampling technique

Abstract

The Delves micro-sampling technique has been applied to the determination of lead and cadmium in paints by atomic-absorption spectrophotometry using both liquid and solid samples. The method involving liquid samples consists in suspending the paint sample in an appropriate solvent and transfering 10 µl of the suspension into a nickel cup. After evaporating the suspension to dryness and pre-igniting the residue in a muffle furnace, the cup is inserted directly into an air-acetylene flame. The concentration of the metal is determined by the method of standard addition. The standard deviation was found to be ± 2·6 per cent. at the 99·4 p.p.m. of lead level at 283·3 nm and ± 1·8 per cent. at the 31·7 p.p.m. of cadmium level at 326·1 nm.

The method involving solid samples consists in directly inserting a weighed amount of paint into an air-acetylene flame. Calibration was accomplished by the method of standard additions. The standard deviation was found to be ± 5·5 per cent. at the 230 p.p.m. of lead level at 261·4 nm and ± 20 per cent. at the 1·7 p.p.m. of cadmium level at 326·1 nm.

Results for lead and cadmium in several paint samples by the two methods agreed well with those obtained by the conventional atomic-absorption method. Both methods are applicable to oil- and water-based paints and the time-consuming steps of ashing and dissolution of the ash required in conventional paint analysis are eliminated. The method with solid samples is more rapid than that with liquid samples, but is less widely applicable because the concentration range of the metal that can be determined is limited.