glycerol

[sepscientologist]

Any advice on measuring glycerol? I can measure at high levels but lower levels disapear and it does not appear to be linear.
Perhaps it is decomposing in the inlet at lower levels or?

Any advice would be much appreciated

[MSCHemist]

I measure 3-MCPD as one of my primary analyses as I work for a company where HVP is a primary product. It is glycerol with a OH replaced with a Cl on the end. It is a long procedure involving derivitization with HFBI on each of the OH's followed by GC/MS SIM mode. My LOD is about 10ppb.

[chromatographer1]

sepscientologist

I would advise you to be a bit more forthcoming in the details of your work if you want any help that would be worth your while, or the time of anyone trying to help you.

One could talk for hours (which here means typing by hand) about possibilities. You don't need a library of methods about every possible matrix that could contain glycerol.

You could be talking about booze, cake mixes, sewer contents, air, gasoline, water supplies, etc.

General advice. Derivitize glycerol.

Don't try to inject it as is
or
this happens:

" I can measure at high levels but lower levels disapear and it does not appear to be linear."

best wishes,

Rod

[sepscientologist]

Thanks guys. Looks like derivatization. I will be looking at residual glycerol in biodiesel waste. Currently
all I have tried is standards and they were not linear.

Sounds like I need derivatization.

Thanks!

[Consumer Products Guy]

We've used capillary GC with BSTFA derivatization to do this for decades, see "Quantitative Determination of Glycerin in Soap by Capillary Gas Chromatography", JAOCS, Vol. 64, No. 9 (September 1987)

We use this also for liquid products, and for similar materials such as propylene glycol, glycol ethers, sorbitol, etc. Very straightforward and easy. Biodiesel should be no issue this way, can also do mono and diglycerides.

[chromatographer1]

Unless your sample has a LOT of water, CPG's suggestion is a good, if not the best, way to go.

Alternatively, TMS-imidazole can tolerate a lot of water.

I would prefer a RI-HPLC method, especially if it is routine, repeated test, but with variable amount of water content.

good luck,

Rod

[Consumer Products Guy]

The consumer products we deal with can have 90% water, so that is not an issue to us.