New TA-MS coupling system with increased sensitivity for low volatile materials

Abstract

The quantitative transfer of condensable gases and vapours from a thermal analysis instrument to a quadrupole mass spectrometer presents technical and physical problems, particularly at high temperatures. This paper describes a new orifice system for coupling a simultaneous TG-DTA unit with a quadrupole mass spectrometer, able to measure quantitatively the vapour pressures of iodine, selenium, tellurium, lead, silver, etc. up to 1200°C. In designing the new two-stage orifice system the laws for gas flow dynamics were considered. A new high temperature furnace guarantees both small temperature gradients within the system and optimal flow conditions (1). The paths for released vapours, i.e. distances between sample, orifices and MS analyser, have been kept as short as possible. The measurements reported demonstrate the greatly increased sensitivity of the new system, particularly necessary when analysing metal vapours.