Vacuum fusion analysis with a mass spectrometer

Abstract

The suitability of a mass spectrometer for vacuum fusion analysis is discussed; the equipment and its mode of operation and calibration are described. The objections to using an oil pump for extracting the gases liberated from the metal samples have been overcome with this apparatus.

Results for oxygen determination in steels, molybdenum and zirconium have been independently checked by using a fast neutron-activation technique, and the results of two methods are shown to be in good agreement.

Oxygen levels of 116 p.p.m. have a standard deviation of 6 p.p.m. and coefficient of variation of 5 per cent. Although most of the work has been carried out on oxygen determinations, nitrogen results are quoted for two standard iron samples showing that the method is also acceptable for nitrogen determinations. Nitrogen levels of 31 p.p.m. have a standard deviation of 3 p.p.m. and a coefficient of variation of 10 per cent.

The limits of detection for the equipment are 0·1 µg of oxygen, 0·1 µg of nitrogen and 0·01 µg of hydrogen.