Abstract: A method for determining total and bound plasma bilirubin. The method utilizes zone fluidics to enable accurate determination of the bilirubin using small volumes of sample and reagents, and significantly reduces dilution errors caused by inherent changes in bilirubin-binding with sample dilution, as well as the effects of weak bilirubin-binding competitors.

Abstract: The present invention is directed to the determination of unconjugated and unbound bilirubin in a sample.

Abstract: A method is taught by which a sample can be analyzed for the selective determination of the total concentration of bilirubin (B.sub.t), the concentration of conjugated bilirubin (B.sub.c), the concentration of unconjugated bilirubin (B.sub.u), the concentration of unbound bilirubin (b), the concentration of unbound, unconjugated bilirubin (b.sub.u) using a unique combination of enzymatic and colorimetric methods in a single assay, so that the potentially neurotoxic, non-albumin bound, unconjugated fraction of total bilirubin in the sample (i.e., b.sub.u) can be measured in a simple, quick and accurate manner. A kit utilizing the same assay is also described. Both kit and methods will be of use to the clinician and general researcher. The B.sub.t, B.sup.c, B.sub.u, b and b.sub.u are determined using spectra, absorption or emission characteristics in combination with kinetic measurements of rates of reaction of chemical processes.