Lead hydride generation: efficiency in persulphate-nitric acid medium and application to the determination of lead in biological samples

Abstract

A persulphate-nitric acid oxidant mixture was used to study several chemical and physical parameters that affect the efficiency of lead hydride generation. The following five sources of interferences were studied in detail: hydride-forming elements, transition metals, alkali and alkaline earth metals, anions and acids. The transition metals Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ improved the hydride yield, Ni being the most effective with a signal increase of 60%. The persulphate-nitric acid method is five times more sensitive (2.0 ng) than, and almost as selective as, the nitric acid-hydrogen peroxide oxidation method (10 ng), and allows the determination of lead in biological samples. For this purpose three different mineralisation mixtures were used in an aluminium block: nitric acid-hydrogen peroxide, nitric acid-sulphuric acid-perchloric acid and nitric acid-ammonium persulphate. For the determination of small amounts of lead, the results of the proposed method agreed well with those given by graphite furnace atomic absorption spectrometry, and is therefore suggested as an alternative to the latter. Lead hydride generation was more efficient with samples (fresh mussel, tomato, hay powder V-10) than blanks, suggesting that the matrix contains several elements that favour lead hydride generation.