The differential elution of drugs from XAD-2 resin.

Biological fluids and tissue extracts prepared according to a previously published method were passed through a column of Amberlite XAD-2 resin for removal of drugs. The differential elution of the adsorbed drugs from the resin was performed by sequential elution of the drugs in four steps. The column was first washed with 30 ml of 0.05M sodium acetate buffer, pH 4.55. Drugs exhibiting acidic or neutral characteristics were then eluted from the column with 100 ml of chloroform in 20-ml aliquots. The column was then washed with 30 ml of 0.1M potassium carbonate, which was discarded. Drugs exhibiting basic characteristics were then eluted from the column with 100 ml of chloroform:isopropanol (3:1) in 20-ml aliquots. Sensitivity of drug detection with this method by thin-layer chromatography was 0.5 mug/ml in a 10-ml sample for nearly all drugs tested.