Detectors 5
Advanced Operation Manual 201
FPD
+
linearity
Several mechanisms produce sulfur emission. The excited
species is diatomic, so that emission intensity is
approximately proportional to the square of the sulfur atom
concentration.
The excited species in the phosphorus mode is monatomic,
leading to a linear relationship between emission intensity
and atom concentration.
FPD
+
Lit Offset
The default Lit Offset is 2.0 pA.
FPD
+
photomultiplier protection
The PMT is extremely sensitive to light. Always turn the PMT
voltage off (which turns off the high voltage to the PMT)
before removing the PMT housing or opening the emissions
chamber. Failing to do this can destroy the PMT.
Even with the PMT voltage off, protect the PMT from room
light. Cap the housing when removed, place it end down to
exclude light, reduce room light level before exposing the
PMT, and so on. A brief exposure (always with the PMT
voltage turned off) will not damage it but prolonged exposure
will cause a gradual loss of sensitivity.
FPD
+
optical filters
The filters are marked on the edge with the transmission
wavelength. Each filter has a small arrow or triangle on its
side which must point toward the PMT when installed.
The sulfur filter is silvery on both sides and transmits at
393 nanometers.
The phosphorus filter is yellow/green and transmits at
525 nanometers.
Inlet liners for use with the FPD
+
Compounds containing sulfur may adsorb on an inlet liner
and degrade the GC’s performance. Use deactivated, clean
liners or a cool on- column inlet, which injects directly onto
the column.
For best results with splitless injection, use liner 5181- 3316.
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