A method determines an analyte concentration in a sample including the
analyte and a substance. The method includes providing an absorption
spectrum of the sample. The absorption spectrum has an absorption
baseline. The method further includes shifting the absorption spectrum so
that the absorption baseline approximately equals a selected absorption
value in a selected absorption wavelength range. The method further
includes subtracting a substance contribution from the absorption
spectrum. Thus, the method provides a corrected absorption spectrum
substantially free of a contribution from the substance.
