VICI D-2-IM - Manual (Page 21)

17
Installation
From this point, the standing current should be observed and logged after any
system change. In addition, logging the standing current (with and without the
column) on a regular basis is an effective monitor of system integrity (leak-
tightness and cleanliness). We also recommend tracking the internal standard
(quantity on column/area count) for sensitivity continuity.
Troubleshooting High Background Current
If the background current does not drop below 2 nA even after a 12 hour bakeout,
there is either a leak in the system or the column effluent is not clean. To see if the
high background current is due to the column:
1. Make sure the controller is in the un-zeroed condition. (Refer to the discussion
about the ZERO push button on page 5.)
2. Completely disconnect the column from the column inlet tube, leaving the inlet
open.
3. Watch the detector standing/background current, indicated in the controller
DISPLAY. If the current remains high, then either the system has a leak in the
discharge gas supply line or the discharge gas has impurities in it. Proceed to
the next section, “Checking for Leaks in the Discharge Gas Plumbing”. If the
current decreases dramatically, then either the carrier gas supply has leaks
and/or contaminants, or the column is the source of contamination and needs
a bakeout. Read the “Column Bakeout Precautions” below before proceeding.
Checking for Leaks in the Discharge Gas Plumbing
Leaks can be detected with hydrogen. A small lecture bottle of hydrogen with a
regulated flow of 10-15 mL/min through a small outlet tube is all that is required.
(This method can only be used to detect leaks on the discharge gas side of the
plumbing and between the column and detector inlet.)
1. Make sure the controller is in its un-zeroed condition. (Refer to the discussion
about the ZERO push button on page 5.)
2. Hold the hydrogen outlet tube at a fitting connection for ten seconds while
monitoring the standing current display on the controller.
3. If the current remains the same, proceed to the next fitting. If the current
increases, there is a leak at that connection. Tighten the fitting and test it again,
repeating as necessary until there is no change in the standing current.
4. Repeat the test for every fitting in the discharge gas plumbing.
5. Reinstall the column according to the instruction on page 14. When the
standing current reaches an acceptable level, the detector is ready for use.
Proceed to the next chapter, “Mode Selection and Setup”. If the current stays
high, use this method to check for leaks at the column/detector connection.
Column Bakeout Precautions
To prevent detector contamination, we strongly recommend disconnecting the
column from the detector during column bakeout procedures.
When the column in reinstalled after bakeout (refer to page 14 if necessary), the
standing current should be at an acceptable level. If you have exhausted these
troubleshooting methods and the standing current is still high, consult the factory.