Conjugated and Unconjugated Bilirubin Determined in Icteric Sera by Direct Spectrophotometry

Abstract

The difference between the absorption curves of conjugated and unconjugated bilirubin is used for determining their ratio. The error due to oxyhemoglobin is eliminated.

Icteric serum is diluted at pH 8.3 and absorbances are read at three wavelengths: 460, 440, and 415 mμ. Per cent unconjugated bilirubin is calculated according to equations given in the text.

The difference between the total amount of bilirubin determined as azopigments and the fraction of unconjugated bilirubin expresses the amount of bilirubin-conjugates in icteric sera where absorbance due to nonbilirubin yellow pigments is negligible.

Values obtained by this method, by the Fog 1964 method, and by chloroform extraction agree within narrow limits.

Key Words:

• Bilirubin
• erythroblastosis
• fetal
• glucuronates
• jaundice
• spectrophotometry