Direct Observation of the Primary Decomposition Products

In the 1980s interest in the mechanism of atomization of substances in electrothermal AAS stimulated investigation of this process by mass spectrometry (MS) techniques [10-19]. Investigation of the thermal decompositions of salts of some metals revealed the presence of low-volatility decomposition products in the gaseous phase, an observation that provided, as already mentioned, a stimulus to studying the mechanism of CDV. The experimental conditions and the results accumulated in these observations are summarized in Table 2.1. 

The experiments were carried out in vacuum and in a nitrogen environment. In vacuum, a miniature graphite heater in the form of a flat platform with the sample deposited on top was placed in the spectrometer chamber evacuated to 

Reactant Medium Sample Heating Metal Containing Tapp Ref. 

As seen from Table 2.1, the low-volatility products (salt molecules, oxides, and metal atoms) appeared in the gaseous phase at temperatures (Tapp) ranging from 340 to 625 K, which correspond to the beginning of thermal decomposition of the salts or their hydrates. The differences in composition of the products observed by different authors should be assigned to differences in the techniques employed and the actual measurement conditions. 

Significantly, in the cases where the samples were heated to their complete evaporation, two peaks were observed (a low-temperature and a high-temperature one). The first of them corresponds to thermal decomposition of the salts, and the second, to that of the oxides (CdO, Cr20s, CuO, NiO, and PbO). 

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