High-performance liquid chromatographic separation of bilirubin conjugates

An assay for separating and quantifying four bilirubin fractions in untreated human serum using isocratic high-performance liquid chromatography

BACKGROUND

The quantification of serum bilirubin fractions has been widely performed with both the diazo-method and an enzymatic method; however, the accuracy of these methods has not been evaluated because quantitative fractional high-performance liquid chromatography (HPLC) reference methods have yet to be established.

METHODS

Samples were analyzed using HPLC and Shodex Asahipak GS-320HQ columns. Human serum was subjected to HPLC using direct injection, then eluted with acetonitrile: 0.3 mol/l phosphate buffer (pH 6.5) containing 1% Brij 35 and 0.08% sodium ascorbate (30:70, v/v).

RESULTS

Serum bilirubin was separated into 4 fractions; retention times of 9.24, 19.92, 24.07, 35.75 min were identified as delta bilirubin, bilirubin diglucuronide, bilirubin monoglucuronide, and unconjugated bilirubin, respectively. Mean recovery was 93.0%-99.2%. Total precision of peak retention time, height and area exhibited <4.26% variation. Detection range was 3.1 to 348 mg/l. Hemoglobin (6 g/l) and immunoglobins produced a small positive interference. beta-carotene (20 mg/l), vitamin-B2 (370 microg/l) and B(12) (9.5 microg/l) did not interfere with this analysis. Results (n=30) with this method were closely correlated to those by Adachi's HPLC method as r=0.9941 to 0.9960, slope=0.88 to 1.27, intercept=-3.2 to +4.9, for each fraction.

CONCLUSIONS

Since this method was a precise quantitative HPLC method for serum bilirubin fractionation, it might be used to evaluate the accuracy and the characteristics of various routine methods for bilirubin measurement.

High-performance liquid chromatographic analysis of bilirubin and biliverdin from jaundiced broilers

A sensitive and rapid high-performance liquid chromatographic (HPLC) method was developed and used for the simultaneous determination of bilirubin and biliverdin in pericardial fluid samples collected from broilers at a poultry inspection site. A photodiode array detector distinguishing the bilirubin (UV 450 nm) and biliverdin (365 nm) was used as an analytical detector for HPLC system. An internal-surface reversed-phase silica support column was used, and the mobile phase consisted of acetonitrile: 0.5 M Tris HCl buffer (20:80, pH 7.2). Bilirubin was detected from all of the jaundiced pericardial fluid samples, and a small amount of biliverdin was detected with bilirubin in some samples. These jaundiced broilers had hepatic or bile duct lesions similar to those found in edible animals. From these results, a working definition of jaundiced broilers for poultry inspection sites was suggested: bilirubin is detectable from pericardial fluid and the carcass is in a state of yellow color change.

Changes in bilirubin pigments secreted in bile after liver transplantation

The species of bile pigments secreted in T-tube fistula bile after liver transplantation were ascertained by high-performance liquid chromatography in 15 patients for 10 days after liver transplant. Nine glycosidic conjugates and unconjugated bilirubin were resolved by the analytical procedure. The principal pigments in bile and their proportions in normal patients were the following: bilirubin diglucuronide = 83.0% +/- 3.1% (S.D.); bilirubin monoglucuronide = 9.7% +/- 1.4% (S.D.); bilirubin monoglucuronide monoglucoside = 4.0% +/- 2.8% (S.D.); and bilirubin monoglucuronide monoxyloside = 1.5% +/- 1.8% (S.D.). All of the other possible glucuronide, glucose and xylose monoconjugates and diconjugates and unconjugated bilirubin were also found, but each was normally less than 1% of the total. In 13 of the 15 transplant patients, a significant depression in proportions of bilirubin diglucuronide and elevation in proportions of bilirubin monoglucuronide were found after the transplant, with an accompanying but generally small increase in the proportions of the minor conjugates. In two patients with rejection of the transplant, the changes were of larger magnitude, with improvement occurring only with recovery from the rejection. In one of these patients, kidney failure was present, and in addition to the diglucuronide and monoglucuronide conjugates, diglucoside and monoglucoside monoxyloside conjugates were found in plasma. The underlying metabolic abnormalities are not clear but likely reflect underlying abnormal intracellular cofactor levels for conjugation. Glycogen depletion with reduction of UDP-glucuronate levels or reduced UDP-glucuronate formation from UDP-glucose, secondary to elevation of UDP-xylose, could potentially account for the changes in pigment excretion.