Jo Boden
Carlos VargasThis Information Applies To: Agilent GC Systems
Issue
Excessive baseline noise can be introduced at different points including sample preparation, sample introduction, separation, and the detector. The excessive background can cause reduced signal-to-noise (detection limit), creating inaccurate quantitative or qualitative results.
Other chromatographic problems are identified in Basic Troubleshooting for GC Systems . Regular maintenance of your instrument in accordance with the recommended maintenance schedule will reduce the incidence of chromatography problems.
Background
Over time sample deposits can accumulate in the analytical pathway and slowly leach out during subsequent sample analyses (Figure 1). The background can be consistently high across the entire sample run, or vary with the temperature program, and can vary significantly when the instrument is run continuously and after sitting idle.
Figure 1. Excessive background noise
1. Normal background with peaks visible, 2. Excessive background with peaks partially obscured
Resolution
Possible sources of ghost peaks and carry over include:
- Sample preparation
Background noise from the sample can be present during the run due to sample preparation:
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Sample introduction system
Perform the GC Condensation Test to determine if the sample introduction system is the source of the contamination.
Possible source of contamination Solution Low quality or contaminated gas supply Check to see if the problems coincided with a change in gas cylinder. If they did, change the gas cylinder and flush the gas lines for sufficient time to clear the volume of the gas system Contaminated gas filter Check the gas filter indicator (if available). If not, replace as per the maintenance schedule or after using contaminated gas Septum bleed or degradation Replace the septum. Use an Agilent high-quality septum appropriate for your inlet temperature. See Replacing the Inlet Septum for Split/Spitless and Multimode Inlets Inlet liner dirty Replace the inlet liner. Use an Agilent inlet liner appropriate for your injection volume, solvent, and injection mode Gold seal is dirty Replace the gold seal. See How to replace the Gold Seal on the Split/Splitless (SSL) Inlet for an Agilent GC Inlet is contaminated Clean or bake out the inlet. See How to Bake-out the Split/Splitless Inlet (SSL) on Agilent GC Systems -
Analytical column
Possible source of contamination Solution Column contamination Bake out the column. Limit the bake-out for 1 to 2 hours
Trim the column: Remove 0.5 to 1 m from the front of the column
Caution: Do not exceed the manufacturer recommended maximum column temperate limit as it will damage your column.Column inserted too far/not far enough into the detector Remove and reinstall the column. See Capillary Column Installation Quick Reference Guide -
Detector
Possible source of contamination Solution Detector contamination Typically detector contamination increases over time and not suddenly. Clean the detector Incorrect detector flow rates Check that the flow rates are within recommended specifications Detector leak (for MS, ECD, TCD) Leak test the detector Old detector filament, lamp, electron multiplier, or ion source Review instrument logs. Clean or replace affected components
If these procedures have not resolved the excessive baseline noise, contact Agilent Technical Support.
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Learn how to effectively troubleshoot your Agilent GC System:
GC-0GEN-1040z - Practical Steps in GC Troubleshooting
GC-0GEN-2040zs - GC Troubleshooting Series e-learning courses available from Agilent education |
