GC after column chromatography

[bubblebubble]

Dear all,
I ran a column chromatograph of a crude methanol plant extract in silica gel (packed with hexane) and got a few column fractions. One had the activity I was interested in. I wanted to know what was the chemical make-up so I sent it through GCMS-I got a propionic acid peak. Its to good to be true to be able to get a pure compound after column chromatography.....any thoughts? I am new to phytochemistry...

[Peter Apps]

The vast majority of organic compounds are not compatible with GC, and so unless you have independent evidence that your activity is in the volatile fraction - can you steam distill it out for example ? - you need to use liquid chromatography, MS, fractionation, purification, NMR etc etc etc to characterize your active compound(s).

Good luck.

Peter

[bubblebubble]

Makes sense. Thank you. I shall look for protocols. Should you have any for guidance, kindly help.

[Don_Hilton]

If you have some kind of activity associated with a particular compound that can be purchased, obtain some, put it in solution at the same concentration, and see if the pure compund gives the activity you think is coming from the fraction you have obtained.

Elution of a plant extract under the conditions you describe - silica gel with hexane and having a few fractions, sounds like a very rough fractionation of the extract.
I would expect that there should be other compunds in the fraction with the propionic acid. This should be one of many compunds that move slowly in hexane across sillica gel - if it will move at all.