| Abstract
| - A highly sensitive enzyme-linked immunosorbent assay(ELISA) has been developed for tetrahydrogestrinone(THG), the new designer anabolic steroid responsible forthe well-known Balco scandal announced in year 2003.Antibodies have been raised against 18a-homo-pregna-4,9,11-trien-17β-ol-3-carboxymethyl oxime coupled tohorseshoe crab hemocyanin. The hapten has been synthesized from gestrinone by controlled reduction of thetriple bond of the ethinyl group at position C-17, withoutaffecting the double bonds of the steroidal rings, followedby reaction of the keto group at C-3 with (carboxymethoxy)amine hemihydrochloride to form the oxime bond. Theantisera obtained has been used in combination with18a-homo-pregna-4,9,11-trien-17β-ol-20-yn-3-carboxymethyl oxime, a hapten derivative of gestrinone, coupled tobovine serum albumin to establish a competitive ELISA.Under the conditions used, THG can be detected in bufferwith a limit of detection (LOD) of 0.045 ± 0.015 μg L-1(N = 9). The assay is very selective since other steroidsassessed are not recognized. Preliminary experimentsperformed with human urine samples demonstrate thatthe assay can be applied to the analysis of these samplesafter a simple sample treatment method reaching a LODof 0.25 ± 0.14 μg L-1. Accuracy is very good as demonstrated by the excellent correlation obtained when analyzing blind spiked urine samples (slope 0.93, R2 = 0.992).
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