168 User Information
Troubleshooting and Error Messages
Chromatographic Results
No peaks or reduced sensitivity
There are no peaks when the sample does not reach the GC
detector. Check the following general areas for problems:
The GC
First verify that the GC works properly. If possible, mount an
automatic liquid sampler (ALS) over the inlet and inject a
sequence of internal or calibration standard directly into the
inlet. If peaks appear then the problem is not in the GC.
The Headspace Sampler gas source
The gas source may be low on gas or set to the wrong pressure.
Check the following gas settings:
• Use 60 to 80 psi for MPC carrier and vial pressurization gas.
• Use a pressure above the pressure inside the sample vial
after equilibration for EPC vial pressurization gas (usually
10 to 20 psi).
• Use the inlet pressure setting for EPC carrier gas.
The sample vial
Check for the sample vial for cracks or a defective seal.
The internal Headspace Sampler flow paths
Check the following areas of the Headspace Sampler flow paths:
• The source gas for vial pressurization is connected to the
correct bulkhead fittings. For example, do not connect the
vial pressurization gas to the MPC inlet when running the
vial pressurization gas in EPC mode.
• The source gas for carrier gas is connected to the correct
bulkhead fittings. For example, do not connect the carrier gas
to the MPC inlet when running the carrier gas in EPC mode.
In GCs with EPC, a lack of flow from the Headspace Sampler
to inlet usually causes an inlet shutdown error.
medium_standard.book Page 168 Tuesday, February 17, 2004 10:14 AM
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