Can we run GC-MS for crude hexane, DCM and methanol extracts to characterize the possible type of compounds present in those extracts? If so then how can we prepare the sample to GC-MS? What solvents can be used for the mentioned crudes?
Yes you may if your compounds of interest are volatile.
PFA sample prep guide
Hello. Of course it is possible...but you might end up with a very thick "forest" of peaks in your chromatogram, and in the worst case you will pollute your GC-MS heavily (needle jammed, dirty injector & column polluted with material that won't exit etc. Not nice.). Without knowning the origin of the extracts, it's impossible to say what kind of compounds you have in your extracts. Do you have ANY idea what to expect, have you done similar tests as in your article in Bangladesh Pharmaceutical Journal? That could give some useful hints...it would at least be good to know if the expected type of compounds are chemically stable at the operation temperature of the injector AND if
they are volataile or non-volatile (=if they need derivatization prior to analysis). Another suggestion is to do TLC of your extracts with different eluent systems (different polarities) and when/if you find a suitable eluent system, do column chromatography of, say, 5-10 g of your extract, perform TLC of the fractions and THEN check different fractions by GC-MS. As solvent for GC-MS you can use Hexane, EtOAc, MeOH, ACN, (CH3)2CO etc. The important thing is that the solvent dissolves your sample completely. Hope it helped you.
Thank you all and specially to Jan Erick for your nice elaborate discussion. first I let you know that this work completely new, has no link with my published work. but as you said it may cause some problem in GC, yes i also agree with you. I have done TLC for these extracts but did not run column. yes it is always good to run fractions rather than the crude either HPLC/LC-MS/GC-MS, but i was little bit confused about GC-MS as it is for volatile compounds. but non polar extracts may definitely contain the volatile stuffs. Your discussion should be very helpful for me.
Thanks again
If you want to characterize the volatile compounds by using GC-MS, you may proceed the extraction of fresh materials with petroleum ether or any other solvent.
Yes, you can, but the separation of components will depend on the column you are using (solid phase and length). Normally, a DB-1 of 30 m gives you quite good resolution for fatty acids, fatty alcohols, steroids and triterpenoids like compounds from DCM extracts (check some of my publications for the method).
You can perform derivatization even using different methods simultaneously (sililation, methylation etc.) so you can obtain chromatogram with different classes of compounds. I suggest to start with highly diluted sample.
I also have problems to prepare Aq and MeOH crude extracts to run GCMS. From your experience before can you suggest what is better methods to characterize compounds in those extracts?