Methanol and Triethylamine analysis

[Bangkok34]

I thought we are talking about headspace all the time

No. Don't have that but may well have to purchase if the acetonitrile extraction does give me joy. Trying that now and so far seems good. Thanks Peter.

Regards

Gung

[Bangkok34]

I now have a slight problem. To check whether I had some TEA left in the aqueous layer I injected this layer directly into my GC. This layer contained a lot of minerals and now I can hardly see any response even for the solvent peak.

I have replaced the liner and the septum but the problem persists. Does my detector now need cleaning?

Is it possible that the capillary column is blocked?

Thanks

Gung

[gcguy]

You could try a liquid/liquid extraction with a non-polar solvent. Adding even more salt would promote the efficency of the extraction. Or I wonder if there is a suitable SPE cartridge available?

[Peter Apps]

Hi Gung

Depending on injector and column tempratures and split ratio you might have deposited some muck in your column. If you remove the column form the gc and examine it against a bright light you might be able to see deposits inside it. If these are close to the inlet end just cut off the affected piece of column - this will not materially affect the resolution. If the deposits are further in you might have to try rinsing the column with methanol or even water, bust check first with the manufacturers that the column is likely to survive this.

A better way to check if there are any analytes left in the aqueous phase is to do another extraction with acetonitrile and then run that - the ratio between the first and second peak areas gives the % of analyte that is extracted each time.

Peter

[Bangkok34]

Hi Gung

Depending on injector and column tempratures and split ratio you might have deposited some muck in your column. If you remove the column form the gc and examine it against a bright light you might be able to see deposits inside it. If these are close to the inlet end just cut off the affected piece of column - this will not materially affect the resolution. If the deposits are further in you might have to try rinsing the column with methanol or even water, bust check first with the manufacturers that the column is likely to survive this.

A better way to check if there are any analytes left in the aqueous phase is to do another extraction with acetonitrile and then run that - the ratio between the first and second peak areas gives the % of analyte that is extracted each time.

Peter

Thanks a lot Peter. Will try cleaning the column and also the double extraction.

Great suggestions.

Regards,

Gung

[oscarBAL]

Hello Gong; I think you could try SPME instead to buy a Head Space; using a very polar fiber; may some one else in this forum could tell you more about it.

Regards.

Oscar

[Bangkok34]

Hello Gong; I think you could try SPME instead to buy a Head Space; using a very polar fiber; may some one else in this forum could tell you more about it.

Regards.

Oscar

Thanks Oscar. I looked this up a few days ago and it sounds like this will indeed be suitable. I am trying to avoid purchasing more equipment though. We'll see what I can do.

Cheers
Alex

[Bangkok34]

Thanks Peter and everyone else who provided help and advice. I am now happy to report. That liquid-liquid extraction with MeCN (as per Peter's suggestion) works a treat. The 2nd extraction of the aqueous layer shows that the MeCN extract contains no detectable TEA or MeOH concluding that a single MeCN extraction is sufficiet.

Very pleased...

Thanks

Alex