22 Troubleshooting
3 Chromatographic Symptoms
Retention Times Not Repeatable
• Replace the septum.
• Check for leaks in the inlet, liner (as applicable), and column
connection. (See “Checking for Leaks” .)
• Check for sufficient carrier gas supply pressure. The
pressure delivered to the GC must be at least 40 kPa (10 psi)
greater than the maximum inlet pressure required at final
oven temperature.
• Run replicates of known standards to verify the problem.
• Check for leaks at the inlet. (See “Leak Check Tips” .)
• Verify that you are using the correct liner type for the sample
being injected.
• Consider if this is this first run. (Has the GC stabilized?)
• If using an FID or NPD and retention times increase (drift),
check the jet for contamination.
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