Varian 450-GC, User Manual

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Pulsed Flame Photometric Detector (PFPD) - Detectors
Varian, Inc. User Manual 450-GC Page: 371
To Maximi ze ... Cons id er ...
Phosphorus
response
•
Install wide bore quartz combustor.
•
Use moderately hydrogen-rich flame.
•
Adjust split valve such that detector is just out of tick-tock.
•
Set detector temperature
≥
300
°
C.
Sulfur response
•
Install narrow bore quartz combustor.
•
Set hydrogen carrier gas flow rate to a value that is near, but
just above, the minimum of the van Deemter curve for the
column and maximum column temperature used.
•
Adjust split valve such that detector is just out of tick-tock.
•
Use optimum hydrogen-rich flame.
•
Increase Air2 to enhance ignition and flame propagation in the
hydrogen-rich flame.
•
Set detector temperature
∼
200
°
C.
NOTE: For some compounds, sulfur response decreases with
increasing detector temperature. Set the detector temperature
as low as possible while preserving chromatographic peak
shape.
Phosphorus-to-
Carbon selectivity
•
Install wide bore quartz combustor.
•
Use hydrogen as carrier gas.
•
Use moderately hydrogen-rich flame.
•
Adjust split valve such that detector is just out of tick-tock, then
turn counterclockwise an additional 1/2 turn.
•
Detector temperature
≥
300
°
C.
NOTE: The Gate Delay can be adjusted to increase or decrease
selectivity. However, as the selectivity increases, the
detectivity often decreases. Set the Gate Delay to balance
these performance criteria at levels that are appropriate to the
application. Also, the gate should be set to open (or trigger) as
close to the main peak as possible rather than before or after.
Setting the gate correctly prevents the h ydrocarbon and
phosphorus responses from overlapping as the flame
propagation slows in hydrocarbon-rich flames.