Hydride generation interface for the determination of inorganic arsenic and organoarsenic by inductively coupled plasma mass spectrometry using open-focused microwave digestion to enhance thepre-reduction process

Abstract

An on-line interface was developed for ICP-MS based on hydride generation. The novelty of the approach resides in the use of an open-focused microwave digestion system to enhance the kinetics of a pre-reduction to elemental form, which is carried out using 2% v/v l-cysteine–0.2 mol dm^–3 HNO₃. This interface was characterized using flow injection to simulate transient HPLC peaks. It allows the total conversion of As^V, monomethylarsonic acid and arsenobetaine to As^III and then to a volatile hydride within a few seconds. The conditions are also applicable to the determination of Ge. Using only 20 µl injections, improvements in sensitivity by a factor of 19 and 10 for As and Ge, respectively, were achieved compared with those obtained by continuous nebulization. The detection limit for both elements (independent of species) was also an order of magnitude lower than that achieved by continuous nebulization, down to 0.06 and 0.08 ng cm^–3 for As and Ge, respectively.