SIMULTANEOUS KINETIC SPECTROPHOTOMETRIC DETERMINATION OF BILIRUBIN AND ALBUMIN IN HUMAN SERUM USING THE DIAZO METHOD

A kinetic-spectrophotometric study based on the reaction of bilirubin with p-diazobenzene sulfonic and sulfanilic acid with sodium nitrite i s described. The simultaneous addition of caffeine reagent, diazo reag ent, and alkaline tartrate, reagents used in the determination of bili rubin, in the presence of albumin leads to a time evolution of absorpt ion spectra. This evolution is proportional to albumin concentration a nd constitutes the basis of a new method (based on the diazo method) f or the determination of albumin. Albumin concentrations determined fro m the proposed method are compared with those obtained by using the br omcresol green method. The method is also applied to the simultaneous determination of bilirubin and albumin in human serum samples. A study of the accuracy in the determination is carried out by means of Youde n's method and the standard additions method. It is conclusively shown that the method is not affected by constant or proportional bias erro rs. Finally, the interference caused by hystidine, tyrosine, lysine, a scorbic acid, and hemoglobin is also studied. (C) 1994 Academic Press, Inc.