Chromatography Forum

Hello, dear colleagues,
I have limited experience in gas chromatography and need some advice. Recently, I developed a method for determining pesticides in water using GC-ECD, following the parameters outlined in the ISO standard. However, I noticed that the specified parameters are designed for a 30m column, whereas I am working with a 60m column.
Could anyone advise on the necessary adjustments when switching to a longer column?
Your insights would be greatly appreciated.

Why not just buy a 30m column? They're slightly cheaper so should save you money in the long run.

I suggest you go to Restek's website and look at their chromatogram modeler. Enter your method info, and compare what it looks like on columns of different lengths: retention times, peak widths, etc. I would guess you don't *need* to change anything but if you're just concerned about performance being "good enough" and not about following a regulation. If you want to optimize performance using a 60m column the modeler will do that for you too, but consider it a 'rough draft" you need to test in real life.

Ms. Vardumyan,

Maintain your linear velocity. Agilent used to have a flow/velocity/pressure calculator on their website (have not looked in a while since I have it downloaded) that you can use to calculate the ISO linear velocity from their specifications. Then you calculate for your situation. Your run will be longer because you have twice the column (although probably not double) so extend the run. Once you have established the appropriate retention order you can start to move from there if you desire.

Best regards,

AICMM

Here's the link to Restek's online calculator:
https://ez.restek.com/ezgc-mtfc