RESPONSE SURFACES FOR THE DETERMINATION OF ARSENIC(III) BY HYDRIDE GENERATION ATOMIC-ABSORPTION SPECTROMETRY AND FLOW-INJECTION

The sensitivity of a how injection hydride generation atomic absorptio n system for dissolved arsenite is reported as a function of pH and so dium tetrahydroborate concentration for several common buffers. The bu ffers considered are acetate, formate, propanoate, butanoate, citrate, phosphate and hydrochloric acid. For the acetate buffer, it was found that the response did not reach a plateau at low pH, but rather passe d through a maximum around pH 6. This 'ridge' in the response surface was found to be more pronounced for lower tetrahydroborate concentrati ons, and a similar effect was observed to varying degrees for all of t he organic buffers. The effect was most pronounced for propanoic acid. Response surfaces were obtained with an automated continuous-flow app aratus under computer control and an efficient experimental design bas ed on continuous variations. The instrumentation and software are desc ribed. Keywords: Arsenic; hydride generation; atomic absorption spectr ometry; flow injection; automation