Chromatography Forum

Anyone have any experience to share with 1-propanol ratio to methanol internal standards for head space GC analysis?

Seeing some issues with system suitability consistency when using 1-propanol as an internal standard - could it be the compound itself?

Any suggestions welcome,

Quinn

Should be OK. May be insufficient extraction time?

I've found that 1,2-dimethoxyethane works well as an internal standard for alcohols for direct injection. AccuStandard sells it neat in 5mL ampules.
Cat# M-GRO-IS-5ML-PAK is 5x5mL pack. It might be more volatile for headspace use compared to 1-propanol. The BP is 85C vs 97C for 1-propanol.

Truly appreciate the responses...

Interesting suggestion on the extraction times... head space injections so perhaps it is in the sample preparation. I'm also curious if slight variations in column installation would create the inconsistencies in integration results.

Both Analysts have intermittently seen the issue, so perhaps it is in the method. The method requires the use of 1-propanol, so I'm unable to change the internal standard at this time.

One of the Analysts suggested carry-over from the head space transfer line, but I would think both the methanol and 1-propanol would be sufficiently volatilized as to not condense in a heated transfer line.

/puzzled

For ethanol analysis I use acetonitrile as an internal standard. It works pretty well. I see tiny amounts of 1-propanol in fussel alcohols and spirits but at the miniscule levels it is at it probably has no impact on results. Still I don't like using an internal standard that may be endogenous in some of the samples.

There is a simple and robust method for the direct determinatin of volatile compounds in ethanol-containing solutions. Practical usage of the method “Ethanol as Internal Standard” is presented, for example, here https://www.youtube.com/channel/UCXgL2c ... qtQ/videos
and here doi.org/10.1051/bioconf/20191502030

Best regards,
Siarhei