Determining the Refractive Index of Human Hemoglobin Solutions by Kramers-Kronig Relations with an Improved Absorption Model

The real part of the refractive index (RI) of aqueous solutions of human hemoglobin is computed from their absorption spectra in the wavelength range $250\mathrm{n}\mathrm{m}-1100\mathrm{n}\mathrm{m}$ using the Kramers-Kronig (KK) relations and the corresponding uncertainty analysis is provided. The strong ultraviolet (UV) and infrared absorbance of the water outside this spectral range were taken into account in a previous study employing KK relations. We improve these results by including the concentration dependence of the water absorbance as well as by modeling the deep UV absorbance of hemoglobin’s peptide backbone. The two free parameters of the model for the deep UV absorbance are fixed by a global fit.