The influence of digests and slurries of sugar on thermal behavior of As using Pd(NO3)2, Pd(NO3)2 + Mg(NO3)2, and Ni(NO3)2 as chemical modifiers was investigated. Influence of 0.2%, 5%, 10% and 35% (v/v) HNO3 on calibration (1.00 - 10.0 µg As L-1) was also done. A volume of 20 µL sample plus 5 µL Pd or 5 µL Pd + 3 µL Mg, or 20 µL Ni was injected into the atomizer of GF AAS. For each modifier, the pyrolysis and atomization temperatures were evaluated by means of pyrolysis and atomization curves, respectively. For sugar slurries, pyrolysis and atomization temperatures (Tp, Ta) found were: without modifier (400° C, 2000° C); Pd (1400° C, 2200° C); Pd/Mg (1400° C, 2200° C) and Ni (1600° C, 2200° C). The values for sugar digests were: without modifier (400° C, 2200° C); Pd (1400° C, 2200° C); Pd/Mg (1400° C, 2200° C) and Ni (600° C, 2200° C). Palladium was selected as the optimum chemical modifier. The lifetime of the graphite tube was ca. 350 firings, the RSD (n=12) for a typical 5.52 µg As L-1 sample was < 2.2% and the detection limit was 2.4 pg As. Recoveries between 80 and 92% of spiked samples were found.
Arsenic; Sugars; Chemical modifiers; GF AAS
