3
Troubleshooting
High Vacuum Symptoms
Thermo Scientific
DSQ II Hardware Manual
135
High Vacuum Symptoms
High Vacuum problems can manifest themselves in two ways. First, an intermittent vacuum
condition (the vacuum pressure in the vacuum manifold fluctuates intermittently) can cause
chromatographic signals to drop out, or, if the pressures exceed the maximum allowed
pressures by
Xcalibur
, then the DSQ II can automatically shut down. Second, if the vacuum is
consistent enough to where it does not exceed the maximum allowed pressure and avoids the
Xcalibur
automatic shutdown, non-reproducible false chromatographic peaks can be
generated in the chromatogram.
Typical fore pressure readbacks are 30-40 mTorr (in EI mode), and typical manifold pressure
(ion gauge readback) is 1-5 x 10
-5
Torr. For CI mode, fore pressure is usually 60-90 mTorr,
with manifold pressures no greater than 9 x 10
-4
Torr.
Running a leak check as part of an automatic tune is a good way to check for leaks. You can
also find vacuum leaks by spraying a gas around the vacuum manifold and looking for the
characteristics ions in full-scan EI. Argon produces
m/z
40. Alternatively, compressed
electronic dusting spray containing an HFC can be used. For example, Falcon
®
Dust-Off
®
and MicroCare
®
Micro-Blast
™
contain tetrafluoroethane, which produce ions at
m/z
69 and
m/z
83.
Automatic Tune reports “Air leak has been detected”.
Possible Solutions
There may be an air leak. Use the procedure described above for finding the leak. The most
common leaks are caused by:
• Tighten the transfer line nut or union
• Check the transfer line or inlet ferrules. Replace them if they are broken.
• Clean dust or debris from the top cover O-ring
• No helium flow from the GC. This causes the DSQ II to suck air through the column.
Содержание DSQ II
Страница 1: ...DSQ II Hardware Manual 120299 0002 Revision C December 1 2009 ...
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Страница 36: ...1 Basic Operations Shutting Down the GC MS System 20 DSQ II Hardware Manual Thermo Scientific ...
Страница 182: ...4 Vacuum System and Gas Inlets Gas Inlet Components 166 DSQ II Hardware Manual Thermo Scientific ...
Страница 198: ...5 Ion Source and Inlet Valve Inlet Valve Upgrade 182 DSQ II Hardware Manual Thermo Scientific ...
Страница 202: ...6 Prefilter and Quadrupole 186 DSQ II Hardware Manual Thermo Scientific ...
Страница 206: ...7 Ion Detector Electron Multiplier 190 DSQ II Hardware Manual Thermo Scientific ...
Страница 242: ...226 DSQ II Hardware Manual Thermo Scientific Index ...