Retention Times Not Repeatable - Agilent Technologies 7890 Series Troubleshooting Manual

3
Chromatographic Symptoms

Retention Times Not Repeatable

42
• Replace the septum.
• Check for leaks in the inlet, liner (as applicable), and column
connection. (See "Checking for
• To Perform an Inlet Leak Check
• To Check for Leaks in a Split/Splitless Inlet
• To Perform a PP Pressure Decay Leak Test
• To Check for Leaks in a Multimode Inlet
• To Perform a COC Pressure Decay Leak Test
• To Perform a PTV Pressure Decay Test
• To Perform a VI Pressure Decay Test
• 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.
• Verify that you are using the correct liner type for the sample
being injected. (See
• Consider if this is the first run. (Has the GC stabilized?)
• If using an FID or NPD and retention times increase (drift),
check the jet for contamination or replace the jet.
• To Replace an FID Jet
• To Check for a Plugged FID Jet
• To Maintain the NPD Collector, Ceramic Insulators, and
Jet
• To Check for a Plugged NPD Jet
Leaks".)
Selecting the correct inlet
Agilent 7890 Series Troubleshooting
liner.)