Troubleshooting help on Separation of peaks

I am currently working on Calibrating a HP 6890 Series GC. I am newer to GC (limited to college experience). I ran close to 20 solvents for my full calibration. Used a series of four for each solvent ranging from 1mL to 10mL. Majority of my solvents came out well and had good calibration curves. However, for two sets of solvents Isopropanol/Ethanol, and Toluene/Normal Propyl alcohol I am having separation issues. I attempted to change the temperature ramping, pressure flows, and even switched the detectors, but with my limited knowledge and not wanting to toy around with too many parts I am unsure what to try next. Thought about switching the column which is currently a 112-2032 J&W Carbowax/20m but again unsure due to previous statement. Looking for some advice or just knowledge to help me out.

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crystalnipp over 4 years ago +1

Hello there. Please see attached. Not sure how well the chromatogram will show, but we achieve separation of ETOH and IPA as well as Tol/NBuOH on a wax. Our set-up is a bit different than yours, we do…

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0 alfausett over 4 years ago

Hi vinqc -

If you are unable to pull apart your co-eluting pairs with flow or temperature, there is likely a chemistry situation between the analytes and the phase. I don't have first-hand experience with the CarboWAX column, but WAX phases are often used in solvents, so you started in an appropriate place. I'm attaching a link to a GC applications catalog released a few years ago. If you search the pdf for 'solvents', you will see many other columns that have been evaluated on various column phases. Each selection will give you basic GC parameters to get you started.

https://www.agilent.com/cs/library/catalogs/public/5991-5213EN_GC_Catalog_Applications.pdf

Are you looking for residual solvents in a finished product? Or more of a solvent purity scope?

Keep us posted on your progress!

Best,
Abbey
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0 alfausett over 4 years ago

Hi vinqc -

If you are unable to pull apart your co-eluting pairs with flow or temperature, there is likely a chemistry situation between the analytes and the phase. I don't have first-hand experience with the CarboWAX column, but WAX phases are often used in solvents, so you started in an appropriate place. I'm attaching a link to a GC applications catalog released a few years ago. If you search the pdf for 'solvents', you will see many other columns that have been evaluated on various column phases. Each selection will give you basic GC parameters to get you started.

https://www.agilent.com/cs/library/catalogs/public/5991-5213EN_GC_Catalog_Applications.pdf

Are you looking for residual solvents in a finished product? Or more of a solvent purity scope?

Keep us posted on your progress!

Best,
Abbey
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0 vinqc over 4 years ago in reply to alfausett

Hi Abbey,

i am looking for residual solvents in the finished product. Though we do test for solvent purity, its just a more rare occasion then the finished product testing. Thank you for the catalog, I will look through it and check to see how the basic GC parameters compare!

I will keep posting about progress as time allows,

Thanks,
Vinny
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