Extraction should be carried out under an extractor hood, with adequate ventilation.
Transfer the sample prepared under heading D to the extraction column.
Rinse the beaker with 10 ml of water and transfer the rinsing water to the column.
Leave the liquid to absorb for four minutes. Elute with 2 × 80 ml of dichloromethane. Collect the eluate in a 300 ml conical flask.
Evaporate the eluate from 2 to 3 ml in a water bath rotary evaporator at 30 °C. (
NB: do not allow to boil dry. U.K.
)
Transfer the concentrated residue to a 4 ml graduated tube with a Pasteur pipette.
Rinse the flask with 1 ml of dichloromethane and transfer the rinsing liquid to the tube. Concentrate the sample to 1 ml under a weak nitrogen stream.
If necessary, transfer the concentrate to auto sampler flask for GC/MS analysis.]