XAD-2 resin drug extraction methods for biologic samples.

The XAD-2 resin extraction procedure is rapidly becoming an important tool for both the clinical and forensic toxicology laboratory. Although different investigators use different elution solvents and techniques, the basic procedure is to adsorb drugs onto the XAD-2 resin and then elute these drugs with an appropriate organic solvent. A number of parameters have been shown to be involved in obtaining good results. These include pH of sample, flow rate, type and volume of eluting solvent. These parameters can be adjusted so that maximum overall drug recoveries are obtained. Since XAD-2 extraction of urine by Fujimoto and Wang [2] was introduced, the procedure has been extended to all types of biologic specimens. Various elution techniques have been reported [12, 13], namely, the differential elution of drugs from the resin into acid and neutral, and basic drug fractions. Overall, the techniques vary from rapid simple procedures for drugs of abuse in urine to more elaborate methods of extraction of autopsy material. The extraction procedure itself is flexible enough so as to suit the needs of almost any toxicology laboratory.

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.