24.3 Principle........................................
Bilirubin reacts with diazotized sulfanilic acid to produce a red-purple-colored
compound called azobilirubin under acidic conditions. The color thus produced is
measured in a colorimeter at 540 nm and compared with that of bilirubin standard.
Direct (conjugated) bilirubin produces immediate color with diazo reagent, and the
indirect (conjugated) bilirubin produces color with diazo reagent only in the pres-
ence of 50% alcohol.
Fig. 24.1 Bilirubin metabolism and elimination
98 24 To Estimate Total and Direct Bilirubin in Serum