This is the machine I’m using
Just noticed that Hugh used 140C here.
So it’s possible I pulled 180C out of nowhere…
So…as pentane and acetone seem to have very similar affinities for the stationary phase (Hayes sepD?!?), my best bet is to start below the boiling point of one of my analytes?
So 40-50C, isothermal for a min or 4, then ramp to something warmer to get everything else moving and through the column. ?!?
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Yeah that’s what I’d do
Subbed for some gc goodness. One day I’ll find an eBay unit with an fid for under 500 dolla
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Yes, that’s exactly it. The iso hold allows for separation. Can you go even lower than 40C on your initial temp?
We currently supply a 3 foot packed column that is one half Haysep R and the other half is Haysep D for this application. We used to just use the Haysep D. The combo column works better.
I would be happy to send you a free Haysep R/D.
I think acetone and pentane separate on this column at pretty much any temperature program, but the one I currently favor is 180 isothermal for 10 minutes.
Call me a 310-214-5092 and I will get the column shipped to you.
Hugh Goldsmith
SRI
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Apparently I am gonna try changing what the column is packed with…
Big thanks to @srihugh1 !!
(And every one else who chimed in).
Had I not run out of time before my plane flight, I probably would have gotten around to the 40C start temp…but guessing and not making progress isn’t my favorite pastime 
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It will always seem more worthwhile in retrospect. You’ve probably heard the old Edison quote “I haven’t failed, i’ve discovered 10,000 things that don’t work”
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As in I wasn’t hallucinating?
that makes me feel better about starting with 180C… 
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I’ m sorry in fact Im not aware of how it works with such packed column. The progressive temperature gradient I and other here advised works well for long capilarry column where solvents are weakly retained.
As Mr Goldsmith appears to favor a hot isothermal approach, I guess the separation relies in that case much more on the interactions of the solvents with this kind of column, rather than on their differences in boiling point.
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The reason I like the isothermal approach is that packed columns drift ( column bleed ) more than capillary columns. So if you just stay at one temperature the signal is stable ( flat ). In the case of Haysep packed columns the temperature program does not affect the separation as much as it would a capillary column. We use a combination of non-polar Haysep D and more polar Haysep R.
The Haysep D does not separate normal butane from ethanol but the more polar Haysep R does.
The Haysep R does not separate methanol from propane but the Hay D does. The combo column solves both problems.
You can still temperature program if you want to and can tolerate the signal drift. For large peaks its a non-issue, but when close to the detection limit its nice to have a flat signal.
Hugh Goldsmith
SRI
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Would a column compensation (substracting a recent blank) be ok for correcting the drift ?
Yes, you can subtract the drift. The SRI software ( PeakSimple ) lets you do this.
But it’s never perfect.
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Grab some scientific data processing software. Origin is probably the broadest solution, but I personally prefer LabSpec. If you want free, there’s a decent open source program called Spectral Workbench. Maybe even buy a book on data analysis. Deconvolution of peaks is by far one of the hardest things to do correctly in data analysis. Now you do have some experimental options as mentioned above, but I haven’t seen anyone get those peaks resolved well enough to just tell by looking. You may need to order standards if nothing else works.
Order standards?!?
MeOH, EtOH,IsoP-OH, pentane, Acetone.
No, I need the correct stationary phase!
I’ll gladly go check out the software though. I’m a sucker for good data analysis.
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Wow, sorry. In my daze I was thinking about the CBC/D10 convolution.
Definitely check out those software choices though. I can provide an older copy of LabSpec if you are interested, but it’s probably easier to find an even newer version.
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That’ll be my fault for the lead in 
Sorry about the misdirection…it’s a specialty of mine.
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No worries! I like talking science even when it’s not the same thing everyone else is talking 
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Did you make any progress with this?
I’m curious if the lower starting temp was the solution or if you still think you need a new column.
Not yet. Just got back to the machine today. Probably going to wait for the new column to arrive…
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