Using the Condensation Test to Troubleshoot the GC Inlet

This Information Applies To: Agilent GC Systems 

Issue

This test isolates the point of contamination to the sample introduction system, which includes the gas supply, gas supply lines, and the sample inlet. It does not include the syringe or autosampler. 

Background

Typical chromatographic features that indicate possible contamination problems include ghost peaks, carryover, excessive baseline noise or baseline drift, and instability. See Basic Troubleshooting for GC Systems .

Steps to Follow

To identify if the inlet is the source of contamination: 

1. Leave the GC between 40 to 50 °C for eight or more hours

2. Run a blank analysis (i.e., start the GC, but with no injection) using the normal temperature conditions and instrument settings

3. Collect the chromatogram for this blank run

4. Immediately repeat the blank run when the first run one is completed. Do not allow more than 5 minutes to elapse before starting the second blank run

5. Collect the chromatogram for the second blank run and compare it to the first chromatogram. If:

   1. Both chromatograms contain few peaks or little baseline drift, the carrier gas, carrier gas lines, gas filters and inlet are relatively clean

   2. The first chromatogram contains a larger number of peaks and baseline instability, any combination of the incoming carrier gas, carrier gas line, gas filters or the inlet is contaminated. See Basic Troubleshooting for GC Systems .

      Tip: Gas supply problems are most likely to occur immediately after changing gas cylinders.

Learn how to effectively troubleshoot your Agilent GC System: GC-0GEN-1001e - Gas Management Best Practices GC-0GEN-1012s - GC Inlets Theory and Operation e-learning courses available from Agilent education