GC Column Bleed

The answer to the following question was provided by LCGC’s “GC Connections” editor John Hinshaw.

Q: What is the best way to minimize GC column bleed? What factors increase column bleed?

A:John Hinshaw: Follow these pointers to minimize GC column bleed:
• Select a low-bleed column type as designated by the manufacturer
• Conform to the specified upper temperature limits
• Avoid injecting dirty samples
• Use split injection when possible
• Use high-temperature low-bleed septa
• Replace the inlet liner when it becomes contaminated
• Keep the the carrier gas free of oxygen and leaks

Column bleed is increased with thicker stationary phase films and larger column inner diameters. Also, not taking care to keep the column inlet section above the ferrule clean during installation can result in increased bleed. A retention gap — an uncoated but deactivated section of column — inserted between the injector and the column inlet can help to trap sample residue, and the retention gap is easily exchanged when dirty.

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