Determination of Absorption Coefficients for Complexes of Humic Acid 1S102H with Copper Ions in the Spectral Range 210–350 nm

Abstract

Absorption spectra were used to determine weight-specifi c absorption coeffi cients for free humic acid (HA) macromolecules and those forming a complex with the Cu 2+ metal ion. This was done using an approach involving measurement of the optical density in the absorption spectrum of the complexes and using known binding constants for binding of HA macromolecules with the copper ion. The weight-specifi c absorption coeffi cients of the complexes {HA-Cu 2+ } at e = 250 nm for [HA] = 5·10 –3 g/L were ec = 155 and 200 L·g –1 ·cm –1 for [CuSO4·5H2O] = 1.25·10 –4 and 2.5·10 –4 M. The values obtained are several times higher than the absorption coeffi cients for the free form of HA, e0 = 46 L·g –1 ·cm –1 .