RADIOIMMUNOASSAY OF BENZOYLECGONINE IN SAMPLES OF FORENSIC INTEREST

A simple and economical radioimmunoassay for benzoylecgonine in human blood or urine is described. Hemolysis, decomposition, common anticoagulants and NaF do not affect the results. A commercially available antiserum is used at a dilution of 1:600. The tracer is radioiodinated p-hydroxybenzoylecgonine. It is prepard by reacting p-acetoxybenzoic anhydride with methyl ecgonine followed by mild hydrolysis and radioiodination by the Iodo-gen method. The product is purified on a disposable silica cartridge and has s specific activity of .apprx. 30 TBq/mmol. Polyethylene glycol is used to separate the bound and free fractions in the assay. The range of the dose-response curve is 0-400 ng/ml benzoylecgonine. The assay is largely specific for benzoylecgonine. Cocaine, ecgonine, methylecgonine and cinnamoyl cocaine have slight or negligible cross-reactivities. The inter-assay coefficient of variation is 7.5% and the recovery of benzoylecgonine from spiked blood is 103%. The cut-off is 20 ng/ml benzoylecgonine for both blood and urine. Radioimmunoassay and high-performance liquid chromatography results agree well. [Cocaine is a local anesthetic and potent sympathomimetic that is abused orally, intranasally, i.v. or by smoking.].