Humic substances as a background electrolyte in capillary electrophoresis

Abstract

Humic substances (HS) as a background electrolyte in capillary electrophoresis afford the possibility to characterise HS/reagent interactions. Thus, added Pb(NO₃)₂ reveals specific characteristic regions in electropherograms that correlate with the salt concentration. These regions form because of the on-capillary complexation of Pb²⁺ with HS: fulvic acid, hymatomelanic acid and humic acid. The formation of two complexes (Pb/HS fractions I and II), which have different mobility, was observed. Each of the HS fractions contains those complexes in a different ratio. Differences in the electropherograms apparently reflect structural differences in the fractions. The peak areas of both complexes have a good linear correlation with the concentration of injected Pb²⁺.

Keywords:

• capillary electrophoresis
• electrophoretically mediated microanalysis
• fulvic acid
• humic acid
• hymatomelanic acid
• Pb²⁺ complexes

Acknowledgements

We thank the Estonian Ministry of Education and Research for financial support (Doctorate Grant No. 0172062s01) and Kati Helmja for technical assistance.