Total and unbound bilirubin determination using an automated peroxidase micromethod

The peroxidase micromethod has been automated to measure total and unbound bilirubin. The apparatus consists mainly of a spectrophotometer monitored by a programmable computer. A comparison with the Alkali Azobilirubin Blue method showed a highly significant correlation of 0.976 for total bilirubin. The correlation coefficient between the automated and the manual peroxidase micromethod was 0.974 for unbound bilirubin. The addition of hemolysates caused minimal effects on the values obtained for total and unbound bilirubin, even at levels of hemoglobin above those usually encountered in sera of infants. An adequate control of the temperature is essential to secure precision and accuracy in the measurements. The analysis requires only 25 μl of serum. The apparatus is portable, easy to operate, and the results are obtained almost immediately. All of these make possible its routine use in the nursery.