Single-pH extraction procedure for detecting drugs of abuse.

If the extract, prepared as described, is too contaminated for reliable analysis, a double small-volume extraction can be used. In this modification, the buffered urine is extracted with 1.0 ml of extraction solvent. After centrifugation, an aliquot of this extract is transferred to a tube containing 100 il of HC1 (0.4 mol/liter). After the mixture has been shaken and centrifuged, the HC1 layer is removed and made alkaline with 50 jl of NaOH (1 mol/ liter). This mixture is then extracted with 50 il of extraction solvent, an aliquot of which is injected into the chromatograph. We have used the described procedure effectively and reliably for longer than a year as a confirmatory test for organic bases, other than morphine and codeine, in urine. We favor the described procedure over other techniques for several reasons. (a) Evaporation of large volumes of