| abstract |
Methods, compositions and elements for detecting a nitrogen-containing compound capable of releasing ammonia upon enzymatic action are described. The method comprises contacting in an aqueous medium a sample suspected of containing such a compound and a novel assay composition comprising at least one enzyme which catalyzes the decomposition of the compound to ammonia and detecting the ammonia by condensation with a beta -diketone in the presence of an aldehyde, preferably formaldehyde, and measuring the color or fluorescence produced by any resulting dihydropyridine. According to a preferred embodiment, the aldehyde is generated in situ and the beta -diketone is polymeric. The foregoing assay composition can be incorporated into single-layer or multilayer analytical elements of the type known in the prior art. A preferred such element comprises an isotropically porous spreading layer in fluid contact with a reagent layer. The spreading layer is most preferably non-fibrous. |