After extracting with water, dry your crude extract by bubbling with nitrogen. If possible, also use drying agents (e.g. Na2SO4, CaSO4, etc.) for thorough removal of water. Then redissolve and dilute your extract in ethyl acetate. Make sure you know the concentration of your extract prior to GC injection. This method is done in our laboratory when we are analyzing aqueous, methanolic, or ethanolic extracts via GC-MS.

Thank you Jovale sir... Concentration of injecting the solution matters in GC MS ? and as you told if I am dissolving in ethyl acetate all the components (which are soluble in watrer) may not be soluble in ethyl acetate.. If such a thing happens?

I think by using GC and GC-MS u can detect only the compounds which are volatile or those that can be made by drivatizations etc. But mostly non volatile compounds are present in the aqueous plant extracts. So to detect these compounds you should opt for other techniques like TLC, HPLC or spectroscopic assays as well. These techniques will give you clear information about the composition of the compounds, present in aqueous extract of plant material.

Plants are mostly made up with carbohydrates. So best way to analyze plant aqueous extract is the HPLC method. You can follow any literature in this area for better knowledge of HPLC operating parameters. Further if you feel some aromatic part also extracted in water solution, then you can dry it and then the mass can be analyzed with GC/GC-MS after redissolving in appropriate organic solvent. In this case, you may have to use various organic solvents to check solubility of all the components.

Thank you ..... could you please explain the term Spectroscopic assays ?

GC is mainly for volatile components... TLC- MS or LC- MS can be good option.

Spectroscopic assays means, qualitative assay methods used for determination of phenolic, flavanoids and other class of compounds. They are colorimetric methods in which we estimate the specific group of compounds under UV or Visible region based on their absorbance of light following Beer-Lambert Law.

Thank you sir

Extract with water, dry your crude extract by bubbling with nitrogen. use drying agents (. Na2SO4), for complete removal of water. Redissolve and dilute your extract in ethyl acetate. Make sure you know the concentration of your extract prior to Chromatography injection.

You can choose HPLC for identifying the known compounds. If you don't know the compounds which present in the extract, then you need to separate the compounds using Preparative TLC / Column chromatography. The purified individual compounds can be identified using UV, IR, 1D-2D NMR & LCMS techniques.