58 Model 5380 PFPD Operator’s Manual
Rev. 3.1
The combustor and wall gas flow rates can be optimized for the installed column,
column gas flow rate, and detector temperature by delivering analyte to the PFPD.
Final optimization can be easily achieved either by temporarily installing a stan-
dard permeation source or by making multiple manual injections of a standard
analyte.
Using a Permeation Source
OI Analytical offers permeation kits for sulfur (Part #290411) and phosphorus
(Part #290429) that include a permeation source and associated hardware.
Installing a permeation source between the injector and the GC column or between
the GC column and the PFPD facilitates delivery of a steady concentration of
analyte to the combustor. Since the permeation rate is a function of temperature
and may be too low at room temperature, the GC oven temperature may have to be
adjusted to obtain a readily detectable emission in WinPulse. However, excessive
heating of the permeation source may alter the diffusion characteristics of the
matrix containing the analyte. Care should be taken not to exceed the upper
temperature limit recommended for the permeation source being used. The recom-
mended temperature range for the permeation sources supplied by OI Analytical
(Part #290452 for sulfur source, Part #290460 for phosphorus source) is 35°–60°C.
Note: When a permeation device is used for the first time, it may be necessary to
heat it at 60°C for 24 hours to obtain detectable emission.
Once a steady permeation rate has been achieved, the PFPD response can be easily
optimized. In order to optimize the operation of the PFPD, the column flow should
be set to the minimum flow rate that will occur during the chromatographic
analysis. Failure to do this may result in the PFPD gravitating toward the tick-tock
mode as column flow decreases due to increasing GC oven temperature. This will
result in elevated PFPD noise. For this reason, it is preferable to maintain constant
column gas flow with an EPC gas flow regulator. The following procedure is used
for installing the permeation device and optimizing the PFPD response.
1. Remove one end of the already installed GC column from the detector. (If
installing a sulfur permeation tube, the injector side may be used, but phos-
phorus tubes must be installed on the detector side of the column.)
2. Install one end of an additional short piece of column (about 18" long) into
one of the two inlets of the permeation chamber using a reverse ferrule nut
(Part #223057) and an appropriate ferrule (Part #208330 for 0.25 mm I.D.
column; Part #196113 for 0.32 mm I.D. column).
3. Install the other end of the short piece of column either into the detector or the
injector. Remove the detector cap, combustor tube, and detector body as
described in Chapter 4, “Installation.” Ensure that the end of the short piece of
column inserted into the detector projects 0.5 mm to 1.5 mm above the top of
the combustor support (see Figure 4.11). Rebuild the detector assembly as
described in the installation section.
!
CAUTION: The
permeation
device should
never by heated
to more than
60°C.
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