Physical behaviour of nickel and copper modifiers used in the determination of selenium by electrothermal atomic absorption spectrometry

Abstract

Scanning electron microscopy and visual examination were used to study the physical changes occurring with temperature when Ni and Cu were used as modifiers for Se. During the pyrolysis stage of the electrothermal atomizer heating cycle, the Ni or Cu matrix was observed to shrink as the metal salt decomposed to the oxide and then the metal. This may have resulted in physical entrapment of Se, which coprecipitated with the excess of modifier salt during the drying stage, and this could contribute significantly to the stabilizing effect of Ni and Cu. Pyrolysis curves for Se in the presence of Ni or Cu show a characteristic dip, or decrease in thermal stability, at a pre-treatment temperature of about 800 "C. However, replacement of the Ar purge gas by H, during the atomizer drying stage eliminated this dip, and this may be due to chemical or physical effects. During the atomization heating stage, the modifiers formed molten droplets, and analyte atomization was governed by its kinetically controlled release from these droplets. This is considered to be the major cause of analyte stabilization during atomization.

Topochemical Speciation of Intercalated Palladium in Graphite by Valence Band X-ray Spectrometry in the Electron Microprobe

“…This phenomenon was introduced to routine GFAAS analysis by Welz et al It offered, on one hand, the possibility of GFAAS analysis of volatile elements. On the other hand, it triggered a lot of research activities devoted to understanding the mechanism of analyte retention of the palladium modifier. − …”

Utilization of a Palladium-Coated Platform and a Methane/Argon Purge Gas Mixture in the Determination of Silicon by Electrothermal Atomic Absorption Spectrometry

“…Other researchers have examined the use of an alternative purge gas or gas mixture during the drying and pyrolysis steps to improve peak shapes and/or sensitivity of Sn (O 2 /Ar) (Rademeyer and Vermaak, 1992), Se (H 2 ) (Mahmood et al, 1995), and Si (CH 4 /Ar) (Schleisman and Bollinger, 1995). In each case the peak profiles are improved and sharpened and the detection limits are improved.…”