Centrifugal analyzer method for total bilirubin in serum by use of diazotized 2-chloroaniline-5-sulfonic acid.

We describe two centrifugal analyzer methods for measuring total bilirubin in serum. Diazotized 2-chloroaniline-5-sulfonic acid is used in both. In the first procedure, ethylene glycol and methanol are used as an accelerator solvent; results correlate well with those by a Jendrassik and Grof method adapted to the centrifugal analyzer, but there is considerable hemolysis interference. In the second method, dimethyl sulfoxide is used with the ethylene glycol/methanol solvent and almost all hemolysis interference is eliminated. For either method, a 15-microliter sample is required. In the second method, instrument response is linearly related to concentration to 250 mg/L and the within-run precision (CV) is about 1%.