E4/E6 ratios

The ultraviolet-visible (UV-Vis) spectra of FIAs and FAs are somewhat featureless in showing a continuous increase of absorbance with decreasing wavelength. The absence of any well-defined UV-vis maxima and minima feasibly results from extended overlap of absorbances of a wide variety of chromophores affected by various substitutions (Stevenson, 1994 Senesi and Loffredo, 1999). Despite these limitations, the ratio of absorbances at 465 nm and 665 nm, referred to as the EJE6 ratio, has been found to vary with the nature of HS and has been widely used for characterization purposes (Stevenson, 1994 Senesi and Loffredo, 1999). In particular, the E4/E6 ratio appears to be inversely related to the MW and the degree of condensation of aromatic constituents of HS and is considered as an index of humification (Kononova, 1966 Chen et al., 1977). 

EVLS functions can be set up for the different selected ratios of scan rates. Then the new coefficients at 02 for El, E2, E3 or 01,02, 03 for E4, E5, E6 EVLS functions must be calculated [22], (ii) The elimination procedure is not limited to the number of particular currents. It can choose currents with different dependences on scan rate and calculate the corresponding elimination functions. 

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