Absorptions spectra of indirect and direct bilirubin

Direct bilirubins in vivo was fractionated into bilirubin diglucuronide, bilirubin phosphate and bilirubin sulfate. Influence of pH concentration on the absorptions maximum of each azopigment was studied. The schift of absorptions maximum was the same in the former two direct bilirubins and the latter moved as nearly as the indirect bilirubin-azo pigment yielded after an addition of methanol. These results was supposed to the difference was based on the structual difference of bilirubin due to the conjugation type of bilirubin.