Combined generator/separator for continuous hydride generation: application to on-line pre-reduction of arsenic(V) and determination of arsenic in water by atomic emission spectrometry

Abstract

A continuous hydride generator is described which incorporates a combined generator/separator. The low acid concentrations necessary in the tetrahydroborate(III)—L-cystein mediated determination of most hydride-forming elements require that the gas is purged from solution. As the hydride transfer reaction is so rapid, this allows both the hydride-forming reaction and the stripping reaction to take place in the same vessel. The system has been further modified to allow on-line pre-reduction of arsenic(V) to arsenic(III) by L-cysteine. Detection limits for arsenic, germanium and selenium are 4, 0.3 and 8 ng ml^–1, respectively, at a sample flow rate of 15 ml min^–1. Application of the system to the determination of arsenic in water is described. Concentrations of arsenic in several Ontario waters were found to be in the range 7–600 ng ml^–1, Interferences from nickel and palladium, two of the most strongly interfering elements in the continuous hydride generation process, are diminished to a greater extent with the system described here than with the conventional high acid continuous system.