Evaluation of absorption and first- and second-derivative spectra for simultaneous quantification of bilirubin and hemoglobin.

We discuss the relative merits of absorption and first- and second-derivative spectra for the simultaneous quantification of bilirubin and hemoglobin, and evaluate single-, two-, and multiwavelength methods. Although both species can be quantified from single- or two-wavelength absorption data, lipids or other absorbing or light-scattering components introduce systematic errors that can be substantially decreased by using first- or second-derivative spectra. Multi-wavelength data-processing methods with derivative spectra permit quantification of components with overlapping spectra and decrease the random error usually associated with derivative methods. A typical least-squares equation for quantifying bilirubin in the presence of hemoglobin and bovine serum albumin from multi-wavelength second-derivative data is y(computed) = 0.999x(prepared) + 0.00 mg/L.