Publication detail

Utilization of In-electrode Coulometric Titration in Humic Research

KLUČÁKOVÁ, M. VIKTORINOVÁ, J.

Original Title

Type

abstract

Language

English

Original Abstract

In this work, the in-electrode coulomeric titration is used for analysis of humic acids in aqueous solutions. The method is based on the galvanostatical reduction of splitting off hydrogen ions at a suitable potential. The method was valited using simple organic acids (acetic acid, benzoic acid, citric acid, oxalic acid, phthalic acid and salicylic acid). It was found that efficiency of the method depends on acid concentration and strength. The limits are concentration of 20 mmol.dm-3 and pKa 5. Humic acids are analysed as extract in solution of sodium sulfate (1,5 % wt.). The efficiency of galvanostatic reduction depended on concentration of humic acids as in previous case. The limit obtained for used sample was 20 g of humic acids per litre. It is well-known that humic acids are soluble in neutral aqueous solutions only partially1. Their carboxylic groups have various strength which influences their solubility and activity in natural systems. Humic fractions rich with carboxylic groups are much more soluble. The composition of dissolved fraction is the dependent on initial ratio between humic acids and aqueous medium. Solubility of humic acids in water and aqueous solutions is thus far from simple as might be expected from their solubility-based definition and a multi-mechanism of their dissolution and dissociation. In contrast to measurement of pH, which deteremines the amount of dissociated hydrogen ions, the in-electrode coulomeric titration gives results corresponding with total content of COOH groups in humic extract. The combination of these two methods can be utilized for determination of pKa of dissolved humic acids without titration. Regarding gradual dissolving of various humic fractions with increasing humic content we can compute mean value of pKa in dependence on initial ratio between humic acids and aqueous medium.

Keywords

humic acids, acidity, coulometry

Authors

KLUČÁKOVÁ, M.; VIKTORINOVÁ, J.

Released

17. 8. 2011

Publisher

Czech Chemical Society

Location

Brno

ISBN

0009-2770

Periodical

Chemické listy

Year of study

105

Number

State

Czech Republic

Pages from

897

Pages to

897

Pages count

BibTex

@misc{BUT74081,
  author="KLUČÁKOVÁ, M. and VIKTORINOVÁ, J.",
  title="Utilization of In-electrode Coulometric Titration in Humic Research",
  booktitle="Chemické listy",
  year="2011",
  journal="Chemické listy",
  volume="105",
  number="18",
  pages="897--897",
  publisher="Czech Chemical Society",
  address="Brno",
  issn="0009-2770",
  note="abstract"
}