Direct Spectrometric Determination of the Concentrations of (Unconjugated) Bilirubin and Conjugated Bilirubin in Serum

Abstract

On the basis of absorption data of most light-absorbing components in serum, including separate molar absorption curves for (unconjugated) bilirubin (UB) and conjugated bilirubin (CB), formulas are constructed for direct spectrometric determination of the substance concentration (c) of UB and CB in adult serum (aS) and infant serum (iS), respectively. One hundred formulas using different number and position of wavelengths were tested by inserting spectrometric data for UB, CB, oxyhemoglobin, methemalbumin, transferrin, and turbid components. The best formulas were evaluated on different groups of sera, and, finally, an empirical adjustment was made on two of the formulas. When c(UB + CB) is more than 20 μmol/1, the standard deviation of the between-series disturbance for c(aS-CB) was 0.1 times c(UB + CB). This is about four times larger than for c(UB + CB) because the moderate difference between the ϵ-curves for UB and CB, compared to the ϵ-curve differences bilirubin - hemoglobin and bilirubin - turbid components, reduces the sensitivity for a single component (ϵ = molar absorption coefficient).

Key Words:

• Bilirubin
• conjugated bilirubin
• direct spectrometric method
• unconjugated bilirubin