Mass spectrometer tuning, effect

Figure 3. The effect of temperature and WHSV on the distribution of selected products from the conversion of pine wood pyrolysis vapors over HZSM-5 catalyst. (Note % of total ion abundance should not be equated with % of neutral products since mass spectrometer tuning and cross sections favor aromatics.)...

In the vast majority of GC-MS applications, the chromatographic conditions employed have little or no effect on the operation of the mass spectrometer. This means that the spectrometer may be tuned for optimum performance and a number of samples containing different analytes can be analysed without operator intervention. This is not the case with LC-MS where the chromatographic conditions will invariably have a significant, compound-dependent, effect on the mass spectrometry conditions required to obtain useful analytical data. 

GC/MS. GC/MS is used for separation and quantification of the herbicides. Data acquisition is effected with a data system that provides complete instrument control of the mass spectrometer. The instrument is tuned and mass calibrated in the El mode. Typically, four ions are monitored for each analyte (two ions for each herbicide and two ions for the deuterated analog). If there are interferences with the quantification ion, the confirmation ion may be used for quantification purposes. The typical quantification and confirmation ions for the analytes are shown in Table 4. Alternative ions may be used if they provide better data. 

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