A rapid, qualitative ELISA test for the specific detection of morphine in serum or urine

We describe a competitive inhibition ELISA technique, with a visual end-point, to detect free morphine in blood or urine. It has a sensitivity of 2 X 10(-7) mol/l using 5 microliter samples. No significant cross-reactivity was observed with other opiate derivatives. The assay has applications as a specific screen for morphine in drug abusers, or to study the metabolism of the drug in the body (as the metabolite, morphine-3-glucuronide, does not cross-react significantly with morphine in the assay).