Coupling of Purge and Trap with GC-MS Systems

There are two fundamentally different possibilities for the installation of a P T instrument coupled to a GC-MS system, which depend on the areas of use and the number of P T samples to be processed per day. 

When the sample is transferred to the GC column, it should be ensured that adequate focussing of the analytes is achieved. For this purpose, GC columns are available with film thicknesses of about 1.8 pm or more, which are used as well for the analysis of volatile halogenated hydrocarbons with GC-MS systems (types 502, 624 or volatiles). The injector system is operated using a split ratio, which can be selected depending on the detection limit required. 

As large quantities of water are also focussed together with the analytes in the case of moist or aqueous samples, removal of moisture in the desorption phase is particularly important with cryofocussing techniques. Insufficient removal of water leads to the deposition of ice and blockage of the capillaries. The consequences are poor focussing or complete failure of the analysis. 

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