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Methanol/Toluene
Posted: Mon Aug 22, 2005 9:12 am
by ozric
Hello all. I am trying to quantify the amount of methanol contaminating a batch of toluene. I am using headspace with an FID. I cant get a linear curve for the methanol standards having tried a number of different standards etc... Any suggestions??
methanol in toluene
Posted: Mon Aug 22, 2005 12:23 pm
by chromatographer1
Why are you bothering doing HS ?
Just do a direct injection of the toluene.
Your sample preparation is probably the cause of the linearity problems.
With 1 µL of toluene in a 22mL vial you should be able to get down to very low levels with HS.
How low are you looking? % 1000 ppm 100ppm 10ppm 1ppm?
This is a very easy application, almost any column will work. Methyl silicone through the intermediate polarities should be fine, any porous polymer capillary or packed will work.
Questions? call or email me. I will be glad to advise.
Rodney George
Senior Research and Development Scientist
Gas Separations Research
Supelco
595 North Harrison Road
Bellefonte, PA 16823
814-359-5737 voice
814-359-5459 fax
rgeorge@sial.com
Posted: Mon Aug 22, 2005 1:24 pm
by ozric
Thanks Rodney...I am using HS as we normally do qualitative work on a wide range of samples,varying constituents and concentrations!!
The methanol content can vary wildly. It has been as high as 6%!
What would you suggest?
Your help is appreciated method development is not one of my strong points...
KISS
Posted: Mon Aug 22, 2005 5:19 pm
by chromatographer1
"Keep It Simple, Silly" is a piece of old but good advice.
I have done 50 ppm to 20% with a simple porous polymer packed column.
FID
20 to 60 mL per min carrier (Helium Hydrogen Nitrogen)
1 to 3 meter packed column, preferably glass 1/4" OD or 1/8" OD FSOT lined SS
Add internal std if desired, isopropanol would work.
Use a chaney adapter 10µL syringe
inject 0.5 to 1.0µL
INJ 180°C DET 200°C
Almost any porous polymer will work. I would suggest Porapak Q or P, or Hayesep D or Q or P 100/120 mesh if you are using clean solvent samples (no non-volatiles dissolved in toluene)
You know my number if any other help is required.
best wishes,
Rod
Posted: Tue Aug 23, 2005 7:48 pm
by mcdonar2000
I'm sorry, but this must be one of the simplest applications out. Previous poster is right, go for direct injection of the toluene sample with an internal standard to improve repeatability (IPA is good). If you prefer capillary columns, then just about any standard column including HP-1 or b. pt column will eat up this separation and give good results.
Good luck (not that you should need it).
Cheers...
Posted: Wed Aug 24, 2005 9:14 am
by ozric
McD
Don't apologise! Thanks for your response.
But I gotta stick with HS!!
HS forever
Posted: Wed Aug 24, 2005 12:18 pm
by chromatographer1
Gotta stick with headspace?
Take 1µL of toluene and place into 22mL vial, heat to 80°C for 5 to 10 min. (see what works best), sample and inject.
Depending upon the inertness of your transfer line and injector, you should have excellent results.
Add internal std if needed.
Again, almost any column will work but I would suggest a Supel Q PLOT or a short micropacked porous polymer column, FSOT SS 1/16" OD, optionally, 1/8" if that works better with your system. Glass if that is all you can use.
Have a great day.
Rod