Biodiesel

[bdh]

Does a person really need cool on column injection for GC analysis of biodiesel? I know ASTM D6584 calls for it, but is it really neccessary? Why or why not?

Thanks

[chromatographer1]

Yes it is necessary if you wish to accurately measure the components as required.

best wishes,

Rod

[Bruce Hamilton]

If you want to measure the components in accordance with the standard methods ( either ASTM D6584-07 or DIN EN 14105 ), then you must use cool on-column injection, and the the derivatisation technique specified ( MSTFA, IIRC ).

If you are performing research, you can use any suitable derivative, and also use alternative injection technques - provided they give you the correct answer. My limited experience with MSTFA was that it could create a lot of artifacts, especially doing reseach trying to monitor reactions of differing lipid feeds.

I was using split injection, as I found cool on-column was inadequate for many of the lipids. They claim OCI avoids discrimination effects, but I suspect it avoids issues associated with active split liners and the use of MSTFA.

I suspect the method also excludes some lipids, as MSTFA can affect recovering of derivatives from lipids with high C12 and shorter chains, such as dairy and coconut, and longer chain PUFA TAGs will polymerise.

Please keep having fun,

Bruce Hamilton

[chromatographer1]

Triglycerides can be sensitive to thermal effects and active sites as well. The accurate measurement of such is very important in this analysis.

best wishes,

Rod