Ultraviolet absorbance titration for determining stability constants of humic substances with Cu(II) and Hg(II)

We describe an ultraviolet (UV) absorbance titration method that can be used to determine complexing capacities ( C L) and conditional stability constants (log K) of humic substances (HSs) with metal ions such as Cu(II) and Hg(II). Two fulvic acids (FA) and one humic acid (HA) were used for this stu...

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Bibliographic Details
Published in:Analytica chimica acta 2008-05, Vol.616 (1), p.115-121
Main Authors: Bai, Y.C., Wu, F.C., Liu, C.Q., Li, W., Guo, J.Y., Fu, P.Q., Xing, B.S., Zheng, J.
Format: Article
Language:English
Subjects:
Analytical chemistry
Benzopyrans - analysis
Benzopyrans - radiation effects
Binding
Chemistry
Copper - chemistry
Copper - radiation effects
Exact sciences and technology
Fluorescence
Fresh Water - chemistry
Humic substance
Humic Substances - analysis
Humic Substances - radiation effects
Mercury - chemistry
Mercury - radiation effects
Metal ion
Reproducibility of Results
Sensitivity and Specificity
Spectrometric and optical methods
Spectrometry, Fluorescence - methods
Spectrophotometry, Ultraviolet - methods
Titrimetry - methods
UV absorbance
Water Pollutants, Chemical - chemistry
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Summary:We describe an ultraviolet (UV) absorbance titration method that can be used to determine complexing capacities ( C L) and conditional stability constants (log K) of humic substances (HSs) with metal ions such as Cu(II) and Hg(II). Two fulvic acids (FA) and one humic acid (HA) were used for this study. UV absorbance of HSs gradually increased with the addition of Cu(II) or Hg(II) after blank correction, and these increases followed the theoretical 1:1 (ligand:metal ion) binding model. The results from the absorbance titration calculation for HSs with Cu(II) and Hg(II) compared well with those from fluorescence quenching titration. The titration of the model compound l-tyrosine with Cu(II) proved the validity of this method, and the K and C L were within 2.3% and 7.4% of the fluorescence quenching titration. The results suggest that the UV absorbance titration can be used to study the binding capacities of HSs and/or dissolved organic matter (DOM) with trace metals. The advantages and disadvantages of the absorbance titration method were also discussed.
ISSN:0003-2670
1873-4324
DOI:10.1016/j.aca.2008.04.003