Abstract: The present invention provides a novel immunoassay for the detection of multiple analytes such as amphetamine and methamphetamine in a single assay of a biological fluid sample. In this assay, a single labelled binding partner is utilized capable of cross reacting at differing sensitivities to antibodies derived from conjugate derivatives of the different analytes such that the presence of the analytes at selected levels of concentration of the analytes singly or in combination can be detected.

Abstract: A reactor/separator device is provided for use in automated solid phase immunoassay. The device is a column, fitted at the bottom portion thereof with a water impermeable disc which can hold immunoabsorbents immobilized antisera, ion exchange resins and the like. When the contents of the column supported by the disc are brought into contact with an aqueous phase containing reagents or reactants by centrifugal force, a chemical reaction is initiated. After reaction, centrifugally applied pressure forces the aqueous phase through the filter disc making it water permeable and separating a desired component for subsequent analysis.