Chromatography Forum

I have some toxi-tubes to use in a student research project, but haven't been told much about them. I am going to add pure urine spiked with a known amount of caffiene and nicotine, and attempt to extract. After gently "shaking" I have been told to extract the top layer and place in a chromatography tube....are there any additional steps to take to ensure a good extraction? Do I need to let my extract dry and resuspend it in methanol or other similar solvent?

Add specimen to Toxitube.
Add some type of internal standard.
QS to volume/line with DI Water.
Mix for 5 minutes.
Centrifuge for 5 minutes.
Transfer top layer to a new culture tube.
Evaporate under Nitrogen at 40 degrees C.
Reconstitute with 100 µL of Ethyl Acetate (GC) or Methanol/Acetonitrile (LC)