Varian 450-GC, User Manual

Page: 171 / 205

Pulsed Flame Photometric Detector (PFPD) - Detectors
Varian, Inc. User Manual 450-GC Page: 411
Change the Detectio n Mode and Reassemble t he PFPD
1. Go to the Adjustments page of the PFPD section.
2. Adjust the Gate Delay and Gate Width to correspond with the emission
profile of the element(s) you wish to detect.
3. Turn on the PFPD electronics.
4. Go to Optimizing the PFPD on page 368 for instructions on optimizing the
performance of the PFPD with the optical filter just installed.
Changing the Combustor Size
Although the PFPD can accommodate both narrow and wide bore quartz
combustors, either quartz combustor will work adequately when operating in
either the Sulfur or Phosphorus mode. If detectivity is not critical, you can
switch between the 2 modes without changing the size of t he quartz combustor.
However, if you require the maximum detectivity for an analysis, the choice of
the appropriate diameter (narrow bore or wide bore) of quartz combustor
depends on the detection mode that is to be used.

Sulfur mode: Use the narrow-bore (2 mm ID) quartz combustor for
sulfur, selenium, or tellurium detection.

Phosphorus mode: Use the wide-bore (3 mm ID) quartz combustor for
all other elements.

S + P mode: Use the narrow-bore (2 mm ID) quartz combustor to
enhance S response. Use a 3 mm ID combustor to enhance P response
or when quenching of S response is a problem.
For column flow rates over 5 mL/min, use t he wide bore quartz
combustor.
Proceed as on page 363.
Replacing a Dirty Combustor
The quartz combustor can become fouled after prolonged use, particularly with
samples containing high levels of organometallics. However, the PFPD has a
remarkable ability to clean itself of many deposits. Therefore, before replacing a
combustor, try baking the detector at high temperature with normal pulse rate
overnight or longer. If this does not restore expected noise and detectivity
levels, proceed as described on page 363.