EVALUATION OF THE HYDRIDE GENERATION TECHNIQUE FOR THE DETERMINATION OF LEAD IN COMMERCIAL IRON-OXIDE PIGMENTS

Two different procedures based on lead hydride generation for determination of lead in commercial iron oxide pigments have been evaluated. As the procedure based on the prior acid-dissolution of the samples to give a 1 M HCl final medium led to a high relative standard deviation (6.5%) an alternative procedure based on the use of slurries was studied. The samples were suspended in water containing 0.01% hexametaphosphate, and lead hydride was generated from a 0.7 M nitric acid and 14% ammonium peroxodisulphate medium by addition of 10% tetrahydroborate solution. In this way, an improvement in reproducibility and sensitivity as well as a saving of time and effort was achieved. The procedure based on the use of a suspension of the samples is therefore recommended.