There are a vast number of such assays in the literature, mainly because
hyperbilirubinemia is the most common medical diagnosis in the newborn.
It's a fairly mature field, so you may find many of the references in
papers from 1960-1980 or so.
I'm not sure how accurate you need to be nor whether you need to separate
certain isomers. I think Tony McDonough in San Francisco published several
papers on HPLC assay of bilirubin, but I don't have the references.
Rod
NIH
Bldg 3, Room 106 MSC 0320
Bethesda, MD 20892-0320
email: rlevine@nih.gov
voice: 1 (301) 496-2310
fax: 1 (301) 496-0599