Chromatography Forum

Hi all,

I will be running an analysis for residual solvents in a pharmaceutical product. The method is by direct injection of a solution of the substance. My issue is that invariably the drug substance itself is involatile compared to the residual solvents and so I will have a gradual build up of residues from this substance on the column with obvious deterioration of the column performance. I though that it could help if I add a pre/guard column before my column so that it takes up the residue and this could be replaced regularly. My question is what type of column should I use for this application? Should I use a piece of the same column material as my analysis column or can I do with a piece of untreated capillary? Furthermore what type of length should I use for the guard column?

thanks and regards.

Either deactivated capillary tubing or coated capillary tubing would work. A guard column of 2m should be enough. But deactivated capillary is not the same as untreated capillary.

If it's not on-column injection, then you can also use a split insert design that will trap most of the non-volatile gunge.

Please keep having fun,

Bruce Hamilton

Dear Omar,

Have you already looked in the European Pharmacopoeia, under "Control and identification of residual solvents". There are detailed procedures for control and identification of residual solvents using headspace gas chromatography. With that method you'll avoid contamination of the inlet / column with your involatile matrix substances.

Best regards