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  • Category :  Agilent Knowledge Portal
  • Entry Type :  Article
  • Product Type :  GC Sample Preparation and Introduction GC Systems
  • Component :  Automatic Liquid Samplers PAL Autosampler Systems
  • Product Name :  6850 Automatic Liquid Sampler 6850 GC System 6890 GC System 7650A Automatic Liquid Sampler 7683 Automatic Liquid Sampler 7693A Automatic Liquid Sampler 7820 GC System 7890 GC System 8850 GC System 8860 GC System 8890 GC System Intuvo 9000 GC System PAL 3 CTC Autosampler System PAL XT CTC Autosampler System
  • Task :  Troubleshooting
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Peak Fronting in GC

Answer

This Information Applies To: Agilent GC Systems

Issue

Peak fronting is present in a chromatography peak when it has an excessive asymmetry with a leading edge. A normal peak is almost symmetrical.  

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

Fronting can be caused by sample solvent, component concentration, injection conditions, column selection, and other reasons. Figure 1 shows no fronting, minimal fronting and excessive fronting. 

      
Figure 1. Peak fronting
1. Symmetrical peak with no fronting, 2. Nonsymmetrical with minor fronting, 3. Nonsymmetrical with major fronting 


Resolution

Possible causes of peak fronting include:

Possible cause of fronting Solution
Column overload (component concentration too high)

Dilute the sample, check that the correct volume has been injected, check the syringe size, decrease the injection volume, or increase the split ratio
Improper injection technique (slow/erratic plunger depression) Check that the syringe plunger is moving freely. The solution should be pulled into the syringe body (no solution left in the needle), and moving freely and fast when plunger is depressed. Use an autosampler
Component highly soluble in the injection solvent (Reverse Solvent Effect) Change the injection solvent or use a retention gap 
Mixed sample solvent with large differences in polarity or boiling points Change the sample solvent 
Improper column installation Remove and reinstall the column. See Capillary Column Installation Quick Reference Guide 
Column contamination Bake out the column. Limit the bake-out for 1 to 2 hours
 Caution
Caution: Do not exceed the manufacturer recommended maximum column temperate limit as it will damage your column.
Trim the column: Remove 0.5 to 1 m from the front of the column


If these procedures have not resolved the peak fronting problem, contact Agilent Technical Support.

 Tip 
Learn how to effectively troubleshoot your Agilent GC System:
GC-0GEN-1040z - Practical Steps in GC Troubleshooting e-learning course available from Agilent education
 
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