Broad Peaks

Broad Peaks

If you are seeing the peaks in the chromatogram starting to get broader, then first perform a couple of checks to ensure there’s not a system fault:

- Check if you have potential for large dead volumes in the GC system. Dead volume is unwanted space in the carrier gas flow path where the sample can linger and results in the peaks becoming broader. Dead volume should be minimised where possible by ensuring the column is fitted correctly and right connectors are being used, as well as inlet liners.

- Check that you’re not suffering from low flow rates, if you haven’t done this already and increase if necessary.

If that all looks good, then it might be that you have a problem with the method parameters:

- An old method transferred from a different instrument may require optimisation, or has a colleague tweaked the method parameters without you realising?

- Are you using the best column for your application? The obvious problem here would be that the column film is too thick for the sample, so you might want to try a column with a reduced film thickness and/or length.

- Are the oven temperatures suitable? Try increasing the GC oven temperature ramp, and/or reducing the GC oven start temperature.

- If you are unsure what would be the best column to use, there are online chromatogram modellers available that will create a virtual method for specific compounds and will allow you to see how different columns and carrier gases change the elution times and resolution.

Comparison of chromatograms before and after a change of method