Abstract: Angiotensin I and iodinated angiotensin I solutions are stabilized against enzymatic degradation by the addition of phenylmethylsulfonyl fluoride (PMSK). Such solutions are used as standards and reagents in immunoassay kits for determinatin of plasma renin levels. Stabilized solutions prepared in accordance with this disclosure can be shipped at ambient temperature which represents a substantial advantage in convenience over previously available solutions of angiotensin I and radioiodinated angiotensin I.

Abstract: An improved immunoassay for methadone is disclosed. The subject radioimmunoassay utilizes a novel antigen, antibody and novel labelled methadone derivatives.

Abstract: Compositions useful for conducting a plurality of different radioimmuno-assays simultaneously and methods for preparing same. The compositions radioimmunoassaya a plurality of labeled antigens and their respective antibodies present in selected concentrations so that the response curves observed for each antigen are essentially superimposable on the response curve of all other antigens present in the composition. Particularly preferred compositions include a mixture of radiolabeled morphine, a radiolabeled 5- or 5,5-substituted barbituric acid, i.e., secobarbital and their respective antibodies useful for performing a bivalent radioimmunoassay and a mixture of radiolabeled morphine, radiolabeled amphetamine, a radiolabeled 5- or 5,5-substituted barbituric acid and their respective antibodies useful for performing a trivalent radioimmunoassay.