Abstract
An omegatron mass spectrometer was employed to detect some extremely small amount of impurities in solids. The gases evolved during a vacuum heat treatment of extra pure samples of oxides, sulfides, and selenides, were analyzed by means of the omegatron mass spectrometer. The detected gases have been NH3, NO, H2S, CO, CO2, CS2, HCl, H2O, and hydrocarbons. The origin of these gases are discussed as follows ; (1) the gases produced by thermal decomposition of reactants which were remained after the sample was made by dry process and/ or the evolution of gaseous imprities which were included during wet process. (2) the gaseous products produced by chemical reaction of impurities with the sample. (3) the evolution of adsorbed gases. (4) the evolution of reagent which was used to store the sample, (5) residual gases in the vacuum system.
The amount of gas evolved (QQ) from these samples was estimated as follows ; in the case of flow method, Q = S∫Pdt and in the case of static method, Q= PV. The consideration on ideal cases shows that smaller amount of impurities less than 1 ppb of the material is detectable. The sensitivity of this method has been.shown to be high and the method has been found to be useful in detection of traces of gaseous impurities less than 1 ppm.
Possible sources of error in quantitative analysis are disct ssed as follows; (1) the gaseous imp, rities remain after the evolution of first heating cycle. (2) the absolute meas Irements of partial pressure and of pumping.speed are difficult for active gases.
