weigh 25 to 150 mg of sample,
depending on the anticipated purity, to obtain a final concentration of 1 mg/ml of analyte salt, into a 25 ml volumetric flask and make up to the
mark with water. The anticipated sample purity is determined empirically.*
Pipette an aliquot of 1 to 5 ml of this solution into a 10 ml glass stoppered
test tube. Add drop-wise a 5% solution of sodium hydroxide until pH 10. Then
add 5 ml of the extracting solvent (e.g., chloroform).
Stopper and invert the test tube at least 10 times or vortex for 1 min and let
stand until the layers separate. Using a Pasteur pipette, transfer the solvent layer
through anhydrous sodium sulphate layer into a GC vial.
Inject 1-2 l of the solvent layer into the GC