The extinction coefficient of human hemiglobincyanide

Abstract

This chapter presents a discussion of spectrophotometry of hemoglobin and hemoglobin derivatives. Many special photometers (hemoglobinometers, oximeters, etc.) presently available for the determination of hemoglobin and hemoglobin derivatives are mentioned only incidentally. Numerous (spectro) photometric methods are developed for the determination of oxyhemoglobin, either as oxyhemoglobin fraction or as oxygen saturation. Many conventional two-wavelength spectrophotometric methods are available, most of them involving the use of an isobestic point in the absorption spectra of Hb and HbO2—for example, a wavelength at which the absorptivity of the two components has the same value. This yields a single, linear relationship between the oxygen saturation and the ratio of the light absorbances of the sample at the two wavelengths used. All methods for the spectrophotometric determination of hemoglobin derivatives depend on the validity of the Lambert-Beer law. Many two-wavelength methods are also used in the determination of common dyshemoglobins in human blood (HbCO, Hi, SHb). In all of these methods, the samples undergo some kind of pretreatment so that, besides the dyshemoglobin species to be determined, only one other hemoglobin derivative is present.