A NEW CONTINUOUS HYDRIDE GENERATOR FOR THE DETERMINATION OF ARSENIC, ANTIMONY AND TIN BY HYDRIDE GENERATION ATOMIC-ABSORPTION SPECTROMETRY

A new continuous hydride generator is described. Its characteristics a re compared with a conventional hydride generator for the determinatio n of arsenic, antimony and tin by using flame atomic absorption spectr ometry. This simple hydride generator combines hydride production and gas-liquid separation in one unit, obviating the use of a separate mix ing/reaction coil and gas-liquid separator. Radioactive tracer studies show that a hydride generation efficiency of over 95% is achieved wit h the new hydride generator and that approximately 90% of monomethylar sonic acid (MMA) is converted to its hydride (methylarsine) within the first 10 s of the hydride generation reaction. Compared to a conventi onal hydride generator, an improved signal-to-noise ratio is achieved and comparable or less interference from transition metal ions is obse rved. Cysteine (1% in the sample solution) is effective in reducing in terferences during the hydride generation processes. In the presence o f cysteine, 10-1000 fold higher amounts of Ni2+, Co2+ and Cu2+ are tol erated in the determination of arsenic, antimony and tin. Cysteine als o enhances the signals of arsenic, antimony and tin by 60, 200 and 40% , respectively. Reaction conditions were optimized by using both the s implex optimization method and one-factor-at-a-time method and results are in good agreement.