Environmental Chemistry

Determination of insoluble soap in agricultural soil and sewage sludge samples by liquid chromatography with ultraviolet detection

  1. Samuel Cantarero1,
  2. Alberto Zafra-Gómez1,*,
  3. Oscar Ballesteros1,
  4. Alberto Navalón1,
  5. José L. Vílchez1,
  6. Guillermo Crovetto1,
  7. Coral Verge2,
  8. Juan A. de Ferrer2

Article first published online: 9 SEP 2010

DOI: 10.1002/etc.303

Issue

Environmental Toxicology and Chemistry

Environmental Toxicology and Chemistry

Volume 29, Issue 11, pages 2470–2476, November 2010

Additional Information

How to Cite

Cantarero, S., Zafra-Gómez, A., Ballesteros, O., Navalón, A., Vílchez, J. L., Crovetto, G., Verge, C. and de Ferrer, J. A. (2010), Determination of insoluble soap in agricultural soil and sewage sludge samples by liquid chromatography with ultraviolet detection. Environmental Toxicology and Chemistry, 29: 2470–2476. doi: 10.1002/etc.303

Author Information

  1. 1

    Faculty of Sciences, Department of Analytical Chemistry, University of Granada, E-18071 Granada, Spain

  2. 2

    Cepsa Química. Avenida del Partenón 12, E-28042 Madrid, Spain

*Faculty of Sciences, Department of Analytical Chemistry, University of Granada, E-18071 Granada, Spain.

Publication History

  1. Issue published online: 9 JUL 2010
  2. Article first published online: 9 SEP 2010
  3. Accepted manuscript online: 9 JUL 2010 12:00AM EST
  4. Manuscript Accepted: 11 JUN 2010
  5. Manuscript Revised: 9 APR 2010
  6. Manuscript Received: 1 MAR 2010

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Keywords:

  • Agricultural soil;
  • Sewage sludge;
  • Soap;
  • Microwave-assisted extraction;
  • Liquid chromatography

Abstract

We have developed a new analytical procedure for determining insoluble Ca and Mg fatty acid salts (soaps) in agricultural soil and sewage sludge samples. The number of analytical methodologies that focus in the determination of insoluble soap salts in different environmental compartments is very limited. In this work, we propose a methodology that involves a sample clean-up step with petroleum ether to remove soluble salts and a conversion of Ca and Mg insoluble salts into soluble potassium salts using tripotassium ethylenediaminetetraacetate salt and potassium carbonate, followed by the extraction of analytes from the samples using microwave-assisted extraction with methanol. An improved esterification procedure using 2,4-dibromoacetophenone before the liquid chromatography with ultraviolet detection analysis also has been developed. The absence of matrix effect was demonstrated with two fatty acid Ca salts that are not commercial and are never detected in natural samples (C13:0 and C17:0). Therefore, it was possible to evaluate the matrix effect because both standards have similar environmental behavior (adsorption and precipitation) to commercial soaps (C10:0 to C18:0). We also studied the effect of the different variables on the clean-up, the conversion of Ca soap, and the extraction and derivatization procedures. The quantification limits found ranged from 0.4 to 0.8 mg/kg. The proposed method was satisfactorily applied for the development of a study on soap behavior in agricultural soil and sewage sludge samples. Environ. Toxicol. Chem. 2010;29:2470–2476. © 2010 SETAC

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