Abstract: A colorimetric assay method for the detection of bilirubin in various liquid samples, particularly biological liquids. A multi-zone analytical element based on this assay method is also disclosed. The assay method employs an interactive mordant composition for bilirubin having one or more binding sites for bilirubin, such composition comprising a hydrophobic organic matrix and at least one charge-bearing cationic group. Upon mordanting of bilirubin by the interactive mordant composition, the mordanted bilirubin exhibits an absorption peak shift of at least 10 nm. and at least a 50% increase in molar extinction coefficient.

Abstract: A method for the determination of bilirubin in liquid samples, particularly biological liquid samples. An assay method, as well as an analytical element, is disclosed. In accord with the assay method there are contacted together a liquid sample containing bilirubin as analyte and an interactive composition containing a bilirubin-active complex, the complex comprising a diffusible, bilirubin-displaceable, detectable ligand bound to a carrier which can also bind bilirubin. As a result of a competitive binding-displacement interaction between bilirubin and the complex, bilirubin binds to the carrier and displaces detectable ligand which can be selectively detected and used to determine the presence or amount of bilirubin. Appropriate carriers and detectable ligands can be chosen on the basis of their first order binding constants.

Abstract: Heterocyclic N-oxides are useful as oxidants in photographic elements or film units.