Screening and confirmation of drugs in urine: interference of hordenine with the immunoassays and thin layer chromatography methods.

Hordenine cross-reacted with various enzyme linked immunosorbent assay (ELISA) or radioimmunoassay (RIA) kits used for the screening of urine samples. Morphine-ELISA kit was most sensitive, whereas etorphine- and buprenorphine-ELISA kits were least sensitive to hordenine cross-reactivity. Hordenine also interfered with the thin layer chromatography of oxymorphone, hydromorphone and apomorphine. The major source of hordenine in humans is beer brewed from barley, whereas the major source of hordenine in horses is canary grass or barley. Therefore, the presence of hordenine in the urine of humans consuming beer or in the urine of horses consuming canary grass may give false positive values when the immunoassay and TLC methods are used for the screening of the urine sample. In order to distinguish hordenine from the opiate drugs, simple and sensitive gas chromatographic/mass spectrometric (GC/MS) and high performance liquid chromatographic (HPLC) methods have been developed in this study.