Chapter 6 75
Maintenance
4. Take care not to dislodge the large aluminum seal washer (Part #288050)
from either the bottom of the detector body or the top of the detector base.
5. Examine the top of the column extending beyond the top of the combustor
support. It should be nearly transparent—the polyimide coating should be
burnt away leaving only a clean section of fused silica tubing exposed. If the
polyimide coating is not completely burnt away, the flame is not terminating
at the bottom of the combustor. The Air 1 flow rate should be increased (or
the H
2
flow should be decreased) in subsequent operation of the PFPD. If poor
performance is the reason for changing the combustor, the detector’s perfor-
mance can be retested by adjusting the gas flows, which may eliminate the
need to replace the combustor. If so, go to “Reinstalling the Detector Body”
in this chapter.
Replacing the Combustor Support
1. Remove the combustor sleeve and store it in a clean plastic bag.
2. Using a clean E/i" wrench, remove the combustor support (Part #280461C for
2-mm I.D. combustor; Part #280453C for 3-mm I.D. combustor) from the
detector base. Place the combustor support onto a clean lab tissue or store in a
clean, sealable plastic bag.
3. Loosen the column nut (Part #223057) in the GC oven and pull the column
down.
4. Using clean forceps, replace the aluminum combustor support washer (Part
#288076) from the counter bore in the center of the detector base.
5. Using a clean lab tissue, place the desired combustor support into the detector
base and finger-tighten. Using a clean E/i" wrench, tighten an additional Q/i–Q/r
turn.
6. Reinstall the combustor sleeve.
7. Carefully slide the column back up through the column nut and into the
detector base until it protrudes beyond the top of the combustor support.
(Refer to the appropriate GC manuals for general instructions on how to
install a capillary column into a detector.)
8. Using a magnifying lens, determine if the column needs to be trimmed. If so,
trim the column using a column scribe and verify that a square cut has been
achieved. Carefully pull the column back down until it is 0.5–1.5 mm above
the top of the combustor support. Tighten the column nut. Check and verify
that the column’s position above the combustor support is still correct.
!
CAUTION:
If the tip of the
capillary tube is
crushed due to
misplacement of
the detector body,
chromatographic
performance will
be impaired and
the column must
be reinstalled.
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