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 1M 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 0.7M 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.