Our method for the butanol determination in the water use AT-624 Column (30mx0,53mmx3mcm). We dilute the sample in the ethanol and use internal standard n-propanol. However the repetability is poor. Have anyone suggest me another method?
By Consumer Products Guy on Wednesday, January 14, 2004 - 06:38 am:
For small alcohols we use a 10 meter 0.53mm PEG-type column, and use n-propanol as internal standard. We dilute samples and standards in water and keep injection volumes to 0.5ul so we don't overload the volume of the inlet, and our reproducibility is excellent, looks like same chromatogram overlaid upon itself.
By Anonymous on Wednesday, January 14, 2004 - 09:57 am:
Don't want to buy another column?
The reason for your problem is that the water is eluting about the same time as your butanol and internal std on the 624 (OV1301) capillary. Your column is flooded and I am certain you will have problems.
I would dilute your sample in another solvent, perhaps DMF or DMAc to reduce your capillary on-column water loading. Unless you are looking for ppb amounts of alcohol, it should be no problem.
Or, use a packed column in glass or deactivated steel to perform the analysis more cheaply but also more effectively. A porous polymer like Chromosorb 101 or Hayesep/Porapak P (lots of vendors carry these) would work nicely, or even a 5% Carbowax 20M on Carbopack B (Supelco). You can use a 1/8" OD or a 1/16" OD column, 6 to 8 feet should be more than enough. Check with your vendors.
By Anonymous on Wednesday, January 14, 2004 - 10:03 am:
"The reason for your problem is that the water is eluting about the same time as your butanol and internal std on the 624 (OV1301) capillary. Your column is
and I am certain you will have problems."
Sorry about the pun. It was unintentional.
By Anonymous on Thursday, January 15, 2004 - 01:11 am:
Thank you for help. Guy-Is PEG column suitable for water injections? Which vendor do you use?
Anonymous-I'll try DMF, we use it a lot.But maybe will not be any difference, because we use ethanol as a solvent 1g sample e.g.water/5ml ethanol.
By Anonymous on Thursday, January 15, 2004 - 06:09 am:
The Peg column will last a long time if you elute the water completely after each injection (cook it off by time or by temperature)
The ethanol(and or water) carrier solvent can also cause plug dispersion of the slightly later eluting peaks (IPA and BuOH) and affect the reproducibility of the analysis, a problem you noted above. The later eluting carrier solvent (DMF) will minimize this effect and should give you superior results.
By Consumer Products Guy on Thursday, January 15, 2004 - 07:02 am:
We normally use 15 m x 0.53 mm Nukol poly(ethylene oxide) fused silica capillary column with 0.5u film thickness (Supelco #2-5326) and the column is 7 years old. We use it for consumer products such as hand sanitizers, liquid detergents, etc., all diluted with water. We've also used in the past used 15 m x 0.32 mm or 15 m x 0.25 mm HP Innowax crosslinked poly(ethylene oxide) fused silica capillary column with 0.5u film thickness (Agilent #19091N-211 or #19091N-231 respectively) but went with Nukol only because it happened to be the only 0.53 mm column of its type that we had at that time. Injecting from water doesn't seem to be any detriment, as long as injection volumes are kept to 0.5ul so the expanded volume doesn't overload the inlet liner capacity.
By Anonymous on Wednesday, January 21, 2004 - 11:18 pm:
It is also possible to determine butanol (and other alcohols, up to about hexanol) using conventional HPLC and a C18 column. Mobile phase: water with refractive index detection.
By Anonymous on Thursday, January 22, 2004 - 01:36 pm:
I have not done this, and I expect the separation of isomer alcohols might not be that good, but this question is in the wrong discussion section.