GC-MS is good but depending on the analytes HPLC-MS is better or more general. Some of the analytes may not be volatile. In a mixture you might want something like a triple-quadrupole mass spec.

Do you want to look for proteins/other macromolecules or small molecules? This affects the ionization you want and the chromatography.

Also are you looking for a set of specific molecules or all molecules?

Hi Dear Mokhtar

this depends on the chemical nature of the plant.

Polar, typically non-volatile compounds such as sugars or hydroxy-carboxylic acids are easier to analyse by LC/MS (HPLC coupled to MS). Apolar, volatile compounds such as terpenes are ideally analysed by GC/MS.

Dear Nosrati, along stated above answers, you can also perform your crude samples in HR-LC-Q-Tof-MS to get phytochemical profile, here I attached a relevant research article for reference. But the accuracy of phytochemical compounds exploration is from isolation, then characterization through LC-MS and NMR.

Dear Mokhtar

as above, I recommend you GC-MS technique for volatile compounds and HPLC technique (eg. HPLC-MS) if your analytes are non-volatile.

Best regards

Monika

Dear Nosrati

If you want to know chemical composition of the extract you should have mass detector. selecting HPLC or GC depends on volatile nature of the compounds. if it contains volatile to semivolatile constituents, GC/MS works. for non volatile, if you wanna analyse it by GC/MS and can guss the compound categorry, derivitization is suggested. e. g. for fatty acid, their methyl esters can be separated on GC. Othervise LC/MS would be of help.

Liquid chromatography is less destructive to the components of biological extracts.