ethanol and isopropyl alcohol separation

[tellest81]

Hey, I wasn't talking about YOU, but about the guy who wrote the USP method.

You are excused as it was a learning experience. But the USP guy should have known better.

best wishes to you.......

Rod

!! sorry!!
the bibliography not mentioned usually use of the HP INNOWAX column...

[tellest81]

sorry rod! i tried your previous methods but even if my peak are more resoluted (thank a lot) with the decreasing of my injection volume and the helium flow, no separation was obtained.

i found as other internal standard for alcohol on this column :
for c6-alcohol: 3 octanol
for methanol and the higher alcohol: 4 methyl 2 pentanol or pentan3ol
for volatile phenols: 3.4dimethyl phenol
these products are not in my sample. there is someone who use also the HP INNOWAX column? what others internal standard can i use? i will compare before paying.

[Consumer Products Guy]

Sorry I wrote "^&%#$%^&$%$##^&#".

I meant &%$#$&@$^&*$$^^#%*%#


Ditch the IPA, use n-propyl alcohol. You need your assay and separation to be robust and the operators not to have issues /difficulties running the assay. Start over if you need to.

[tellest81]

i forgot to say that, the internal standard that i have chosen in my last message were been very good for my analyses !!

[jgarey]

I've gotten good resolution between IPA and EtOH using a Stabilwax 30m x .32 x 1um column. I think I originally tried the same innowax column you are using but had to change to a column with a greater film thickness to get good resolution. I had to use the wax instead of 624 because of the co-elution of IPA and ethyl formate on the 624. But I don't think you will be able to separate IPA and EtOH on your current column.

[tellest81]

I agree with you jgarey. thank a lot for this recommandation. it is useful for an other application. I changed the internal standard (IPA by the methyl3pentan2ol because this column allowed me to get good compounds separation.

[Consumer Products Guy]

Separation of ethanol and IPA can be important as well in the consumer products business. For example, Purell Advanced hand sanitizer gel has 70% ethanol as cGMP active, but also has a few percent IPA in the formulation as well. So Purell OTC analysts and QC operators need to separate the ethanol from the IPA and any other components for their validated cGMP assays.

[Karen01]

When I wanted to separate acetone, acetonitrile, methanol, ethanol, IPA, nPrOH, and many other solvents at the same time I put a 3 meter piece of wax capillary in front of a 30m 624 capillary.

For the solvents you listed (and few more) I know a Blood Alcohol column works well and all those can done in a short time isothermally.

- Karen

[dpr]

Have achieved good seperation of Alcohols and actone using a poraplot column on FID.
We used a 50m column but that was for sample matrix reasons.
A 10-20m column should do the job just as well for the various alcohols in water.

[CharapitsaS]

Hi!!!

I have since the last few days a co-elution problem of ethanol and isopropyl on my new column Agilent HP-INNOWax
19091N-133 30 m x 0,25 mm, 0,25 μm, recommended for better separation of alcohols. to analyse my sample i use the following program
Helium 1 ml/min, 35°C, constant flow
oven : 35 °C during 6 min
35 à 150 °C at 5 °C/min
150 à 250 °C at 15 °C/min
250 °C during 2 min
Splitless Injection, 220 °C (in waiting of a split liner)
vol injected: 1 μl

the others molecules in my sample are very well separated due to their polarity, but the ethanol and isopropanol (isopropanol was the internal standard) are not separated. which is not theoretically logical. so I equilibrated the column, Check for leaks. I find always with the same problem. therefore, I removed isopropanol by acetonitrile : another co-elution . I am in search of appropriate maintenance to perform elution . I work with an Agilent GC 7890A Series MSD. does someone can help me?

Dear Tellest81 !

May be method "Ethanol_as_ISTD" ( http://www.inp.bsu.by/labs/lar/eis.html ) will solve your problems.

Regards,
Siarhei

[chromatographer1]

Not knowing all the solvents and the concentrations thereof, it is difficult to give you solution.

The solution I gave earlier separates methanol, acetaldehyde, ethyl ether, ethanol, IPA, nPrOH, Methyl acetate, EtoAc, DCM, hexane, Isobutanol from ethanol.

Perhaps you might wish to share why the 624 (1301) capillary won't do the job for you. The Alc colum Karen mentioned also will separate many of these solvents.

Good luck,

Rod

[Peter Apps]

Hi!!!

I have since the last few days a co-elution problem of ethanol and isopropyl on my new column Agilent HP-INNOWax
19091N-133 30 m x 0,25 mm, 0,25 μm, recommended for better separation of alcohols. to analyse my sample i use the following program
Helium 1 ml/min, 35°C, constant flow
oven : 35 °C during 6 min
35 à 150 °C at 5 °C/min
150 à 250 °C at 15 °C/min
250 °C during 2 min
Splitless Injection, 220 °C (in waiting of a split liner)
vol injected: 1 μl

the others molecules in my sample are very well separated due to their polarity, but the ethanol and isopropanol (isopropanol was the internal standard) are not separated. which is not theoretically logical. so I equilibrated the column, Check for leaks. I find always with the same problem. therefore, I removed isopropanol by acetonitrile : another co-elution . I am in search of appropriate maintenance to perform elution . I work with an Agilent GC 7890A Series MSD. does someone can help me?

Dear Tellest81 !

May be method "Ethanol_as_ISTD" ( http://www.inp.bsu.by/labs/lar/eis.html ) will solve your problems.

Regards,
Siarhei

Take a look at viewtopic.php?f=2&t=18782&hilit=ethanol+as+ISTD on this forum for some discussion of Siarhei's proposal.

Peter