Flame Photometric Detector (Fpd); Optimizing Fpd Sensitivity And Selectivity - HP 5890 Series II Plus Reference Manual

Detector Systems

Flame photometric detector (FPD)

Flame photometric detector (FPD)

Optimizing FPD sensitivity and selectivity

FPD sensitivity and selectivity are affected by several important
parameters. These are listed below, with suggested ways to optimize for
each application.
A. FPD Flow Rates. FPD flow rates are the most critical for optimizing
either sensitivity or selectivity (these do not necessarily have the
same optimal conditions). The most critical flow parameter is the
hydrogen/air (or hydrogen/oxygen) ratio. Less critical are the
auxiliary nitrogen/carrier combined flows.
A suggested way to set near•optimalflows is to begin with
recommended flow rates located in the HP 5890 Operating Manual.
Then vary each gas until a local maximum is reached. Optimize
hydrogen first, then air (or oxygen), and lastly the auxiliary nitrogen
flows. This may require a couple of iterations (tries). Adjusting these
flows is most easily done by just varying the supply pressure
regulator setting. Figure 7•1 1 plots approximate FPD flows versus
supply pressure for all FPD gases.
Note: Take care that adjusting the supply gas pressure does not
change some other flow supplied by the same regulator.
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