Chromatography Forum

Hello I have been attempting a fiehn like derivatisation (methoxyamination followed by TMS derivatisation), but I am not confident it is working perfectly as I am unsure if I get any methoxyamination products. This is on a plant matrix. I can clearly get the TMS products, but am unsure of common methoxyaminated products to look for.

I am looking for a suitable internal standard and I tested corticosterone (as contains both hydroxy and carbonyl functional groups), but this did not seem to show up in the sample matrix. I tested and sugar for the TMS part and this seems to work fine and a single carbonyl containing compound and this seemed to work for the methoxyamination part, but when I try a compound that contains both functional groups it doesn't seem obivous if it has worked.


So was wandering if anyone had any experience of this reaction and suggest any alternative standards to try. Or any common compounds to look out for to test to see if the reaction is working fully.

Sugars DO contain hydroxils and carbonyls. Actually the methoximation reaction is performed to derivatize sugars

Yes sugars contain carbonyl in the chain form I always thought in aqeaous media the ring form is more likely.

sugars are in the closed chain form also when dry. Anyway, you run the Fiehn derivatizion on dry samples

I prefer paan (peracetylated aldonitrile derivatives.
Blow down sample
add 200 ul of hydroxylamine in pyridine
heat 100 deg C for 1-2 hours
cool
add 200 ul acetic anhydride
heat 100 deg C for 1-2 hours
add 0.5 water and 0.5 MeCl2 (looking to replace with toluene next time I run)
inject MeCl2 layer.

It works well on mono and disaccharides. Can be less sensitive and precise with fructose (ketoses) as the resulting derivative is a cis and trans oxime peracetate otherwise each sugar gives one derivative peak.