Selection of Most Suitable Mode for MS Operation

Together with determination of the optimum GC operating conditions, selection of an apropriate MS mode is of primary importance in conducting a successful GC-MS analysis. 

Under the operating conditions employed in the Cl mode, the reagent gas, e.g., methane, can also act only as a moderating gas to produce a high population of near-thermal energy electrons which are captured by the sample molecules (Harrison 1983). Formation of negative ions by interaction of these electrons and sample molecules (AB) can occur by three different mechanisms (Hunt et al. 1976)  

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