Detection and Measurement of Total Bilirubin in Serum, with Use of Surfactants as Solubilizing Agents

Abstract

Abstract We describe a new method for measuring total bilirubin in serum. Nonionic, cationic, or anionic surfactants can be used as solubilizing agents to promote the diazo coupling of indirect-reacting bilirubin. A representative surfactant—azobilirubin system is illustrated, in which absorbance is maximum at 560 nm and linear to a concentration of 200 mg of bilirubin per liter. At pH 2.5 and in the presence of Du ponol (an anionic surfactant), bilirubin is completely coupled within 6 mm at 37 °C. All ingredients required for an assay are combined in two dry reagents, which are stable for a year at room temperature. Sensitivity is comparable to that of procedures routinely used in clinical laboratories; precision, linearity, and stability of the reagents in solution are excellent. Results for fresh sera correlated well with those obtained by the Jendrassik—Grof method. Hemolysis is minimized and turbidity eliminated.