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 are compared with a conventional hydride generator for the determination of arsenic, antimony and tin by using flame atomic absorption spectrometry. This simple hydride generator combines hydride production and gas-liquid separation in one unit, obviating the use of a separate mixing/reaction coil and gas-liquid separator. Radioactive tracer studies show that a hydride generation efficiency of over 95% is achieved with the new hydride generator and that approximately 90% of monomethylarsonic acid (MMA) is converted to its hydride (methylarsine) within the first 10 s of the hydride generation reaction. Compared to a conventional hydride generator, an improved signal-to-noise ratio is achieved and comparable or less interference from transition metal ions is observed. Cysteine (1% in the sample solution) is effective in reducing interferences during the hydride generation processes. In the presence of cysteine, 10-1000 fold higher amounts of Ni2+, Co2+ and Cu2+ are tolerated in the determination of arsenic, antimony and tin. Cysteine also enhances the signals of arsenic, antimony and tin by 60, 200 and 40%, respectively. Reaction conditions were optimized by using both the simplex optimization method and one-factor-at-a-time method and results are in good agreement.