METHOD OF ANALYZING GAS BY COUNTERCURRENT PRICIPLE

摘要

PURPOSE: To achieve clear distinction between finger prints in the same structure without using any soft ionization by performing control so that no mass analysis is displayed from a gas with high molecular weight. CONSTITUTION: A gas to be analyzed is supplied via an entrance valve 4 at the discharge side of a molecular pump 2 or its corresponding middle entrance. The molecular pump 2 is driven by a motor with a regulator 6 for setting a rotary speed. Then, when the rotary speed of the pump 2 is increased, a light molecule forms a countercurrent from a pumping direction and is carried to a mass analysis cell 3. The compression ratio of the pump 2 depends on the rotary speed of the pump 2. Therefore, by controlling the ratio between a partial pressure and a primary vacuum pressure to a specific ratio, propane can still reach the mass analysis cell 3 but has a peak due to such a mass 43 as carbon dioxide and all substances that generate similar fragments with another peak by a mass 4 cannot reach the mass analysis cell 3, thus distinguishing finger prints in a similar structure.