Direct Spectrophotometry of Total Serum Bilirubin in the Newborn

A simple, rapid direct spectrophotometric method for the determination of total serum bilirubin on a micro basis, with a 1:21 dilution of serum in phosphate buffer, is presented for use with the Junior Coleman spectrophotometer. The formula, mg./100 ml. bilirubin = 50 A455 - 119 A575, is applied, where A represents the absorbancy at the wave length specified. The method for obtaining this or a similar equation is presented. The spectrophotometric method, when applied to sera obtained from newborns, gives apparently reliable results in the presence or absence of hemolysis. An evaluation of the method and its limitations is presented.