1998 Volume 71 Issue 6 Pages 1385-1390
The behavior and effect of cobalt as a chemical modifier for lead were studied by electrothermal atomic absorption spectrometry using a tungsten furnace. The characterization of materials formed on the tungsten surface at the charring stage was performed using of a scanning electron microscope and X-ray photoelectron spectrometer. The experimental results indicate that the effect of a cobalt modifier is related to the formation of granular cobalt crystals during a pre-heating stage. Under the coexistence of lead, however, the cobalt crystals became irregularly shaped, probably forming an intermetallic compound between cobalt and lead. By an examination using sample materials containing chloride, nitrate, and sulfate salts, it was found that a cobalt modifier is effective for suppressing the interference of chloride and nitrate. All of the sulfate salts gave negative interference; the cobalt crystal, which acted as a chemical modifier, was included inside a large crystal which originated from the sulfate at the charring stage. The thermal stability of lead is difficult to maintain with increasing sulfate salts. The cobalt modifier was applied to the determination of lead in several water samples.
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