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  • Category :  Agilent Knowledge Portal
  • Entry Type :  Article
  • Product Type :  GC Systems
  • Component :  GC Inlets GC System
  • Product Name :  6850 GC System 6890 GC System 7820 GC System 7890 GC System 8860 GC System 8890 GC System Intuvo 9000 GC System
  • Task :  Troubleshooting
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Loss of Peak Resolution in GC

Answer

This Information Applies To: Agilent GC Systems

Issue

Loss of peak resolution can be a combination of decrease in separation and increased peak width. Loss of resolution can impact on analytical reproducibility and accuracy.

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

 Loss of resolution can be caused by decreasing separation between peaks or an increase in width of peaks (Figure 1):

          
Figure 1. Decrease in peak separation and peak broadening
1. Normal retention time separation, 2. Retention time difference, 3. Peak width at half height
4. Decrease in separation, 5. Increase in peak width

 
Possible cause of decrease in separation Solution
Change in column temperature (all peaks) Check the column temperature
Change in column dimension  Verify that the installed column matches the configured column in the instrument and the method column.
Trimming the column many times over its lifetime will change the effective column length, and impact retention times. Adjust instrument set column length every time the column is trimmed 
Coelution with another peak Improve peak separation. Change column temperature or stationary phase

 

Possible cause of increase in peak width Solution
Overloading from a large change in analyte concentration Dilute the sample
Change in sample concentration (higher concentrations have wider peaks) Check if new standards have been recently prepared. Changes may also be caused by preparation error, degradation, evaporation, or variances in sample temperature or pH
Column contamination Bake out the column. Bake-out for 1 to2 hours or until baseline is stable 
 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. Trimming the column many times over its lifetime will change the effective column length, and impact retention times. Adjust instrument set column length every time the column is trimmed 
Column activity (active compounds) Irreversible. Replace the column
Change in carrier gas flow Check the carrier gas flow rate
Change in the injector settings Check injection volume, purge activation time (splitless only), split ratio, septum purge flow, column temperature
Improper solvent effect, lack of focusing (splitless) Lower initial oven temperature, choose a different solvent, sample phase polarity match, use a retention gap

 

 If these procedures have not resolved the resolution 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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