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

TL;DR

This paper improves the calculation of the refractive index of human hemoglobin solutions by refining the absorption model and accounting for water's concentration dependence, using Kramers-Kronig relations over a broad spectral range.

Contribution

It introduces an enhanced absorption model for hemoglobin solutions that incorporates concentration dependence and deep UV absorbance, improving RI estimation accuracy.

Findings

More accurate RI values for hemoglobin solutions.

Effective modeling of deep UV absorbance.

Quantified uncertainty in RI calculations.

Abstract

The real part of the refractive index (RI) of aqueous solutions of human hemoglobin is computed from their absorption spectra in the wavelength range $250\,{\rm nm} - 1100\,{\rm nm}$ 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.