DETERMINATION OF ARSENIC IN A NICKEL-ALLOY BY FLOW-INJECTION HYDRIDE GENERATION ATOMIC-ABSORPTION SPECTROMETRY

The development of a method for the direct determination of trace arsenic quantities in nickel alloy digests, by flow injection hydride generation atomic absorption spectrometry, is described. An optimization study of the manifold and chemical parameters produced system performance, in terms of tolerance of the nickel matrix and sensitivity, such that matrix removal and pre-reduction of As(V) to As (III) prior to arsine generation were eliminated. Full recovery of the As(V) signal from a solution containing 5 ng ml-1 in the presence of 60-mu-g ml-1 nickel was obtained. Validation of the method was achieved by analyzing a British Chemical Standard (BCS) Certified Reference Material (CRM) #346 IN nickel alloy containing arsenic at a concentration of 50-mu-g g-1. Following dissolution in nitric and hydrofluoric acids by a microwave assisted procedure, the only subsequent preparation required was dilution by the appropriate factor. Up to 60 injections h-1 may be made, with a detection limit of 0.5 ng ml-1 arsenic (250 pg absolute) as As(V) in a 500-mu-l sample. The peak height characteristic concentration is 0.46 ng ml-1, with a relative standard deviation of 3.5% for a 10 ng ml-1 As(V) standard (n=6).