Gas flow detectors

Column temperature Injection port temperature Detector Gas flow rates... 

Decrease the carrier flow and then check the detector gas flow rates. 

WDXRF systems commonly use one or more of the following detectors gas flow proportional counter (flow counter [FC]), sealed gas-proportional counter, and scintillation counters (SC). 

The optimized detector gas flow rates are different for N and P detection and also from that of the FID. Formation of CH radicals is suppressed in the NPD. The NPD is a selective detector for N- and P-containing compounds and the MD is about lOpgN and 5 pg P. Other detector characteristics can be found in Table 2.4. The NPD is used, for example, for pesticide determination in food and environmental applications. 

Once the open tubular column has been properly installed into the gas chromatograph and tested to be leak free, set the column and detector gas flows. Before heating the column, allow the system to purge with carrier gas at ambient temperature for at least 30 min. 

B molecular mass of hexadecane, and 16 B number of carbon atoms in hexadecane molecule. The measured RRF for each component in the test mixture must be within 10 % of the theoretical value as calculated with Eg 5 or summarized in Table 1. If this is not attained, it will be necessary to vary the injection volume, restrictor position, or detector gas flows, or combination thereof, until agreement is attained. 

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