Preferential solvation in the THF–water mixtures. Dissociation constants of acid components of pH reference materials

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Dolores Barrón, Salvador Butí, Montserrat Ruiz and José Barbosa


Abstract

Dissociation constants of acid components of pH reference materials in tetrahydrofuran–water mixtures containing 0, 10, 20, 30, 40, 50, 60, 70 and 100% (w/w) tetrahydrofuran, THF, were obtained. Dissociation constant values determined were: pK1 and pK2 for tartaric and phthalic acid; pK1, pK2 and pK3 for citric acid; pKa for acetic and boric acid and pK2 for phosphoric acid. These values are essential to the determination of the reference pHS values of the standard buffer solutions, which are needed for accurate pH measurements in THF–water mixtures. In order to explain the variation of the pKa values obtained over the whole composition range studied, the quasi-lattice quasi chemical (QLQC) theory of preferential solvation was applied. To identify the solvent characteristics affecting the pKa values, the results are discussed in terms of average macroscopic properties of the mixed solvent and in terms of the solvation shells around the solute. Thus, the methodology of linear solvation energy relationships (LSER) was used to relate pKa values with parameters of THF–water mixtures. The equations obtained allow calculation of the pKa values of substances in THF–water mixtures.


References

  1. C. F. Poole and S. K. Poole, Chromatography Today, Elsevier, Amsterdam, 1991 Search PubMed.
  2. A. K. Covington, R. G. Bates and R. A. Durst, Pure Appl. Chem., 1985, 57, 531.
  3. P. R. Mussini, T. Mussini and S. Rondinini, Pure Appl. Chem., 1997, 69, 1007 CAS.
  4. J. Barbosa, D. Barrón and S. Butí, Anal. Chim. Acta, 1998, submitted Search PubMed.
  5. M. F. Camoes, M. J. Guiomar Lito, M. I. A. Ferra and A. K. Covington, Pure Appl. Chem., 1997, 69, 1325 CAS.
  6. Y. Marcus, J. Chem. Soc., Faraday Trans. 1, 1988, 84, 1465 RSC.
  7. J. Barbosa, D. Barrón, R. Bergés, V. Sanz-Nebot and I. Toro, J. Chem. Soc., Faraday Trans., 1997, 93, 1915 RSC.
  8. J. Barbosa, I. Marques, G. Fonrodona, D. Barrón and V. Sanz-Nebot, TRAC-Trends Anal. Chem., 1997, 16, 140 CrossRef CAS.
  9. W. Cheong and P. W. Carr, Anal. Chem., 1988, 60, 820 CrossRef CAS.
  10. J. H. Park, M. D. Jang, D. S. Kim and P. W. Carr, J. Chromatogr., 1990, 513, 107 CrossRef CAS.
  11. Y. Marcus, J. Chem. Soc., Faraday Trans., 1994, 90, 1751 Search PubMed.
  12. J. Barbosa and V. Sanz-Nebot, Anal. Chim. Acta, 1991, 244, 183 CrossRef CAS.
  13. J. Barbosa, D. Barrón and S. Butí, Electroanal., 1998, submitted Search PubMed.
  14. E. Powell and M. A. Hiller, J. Chem. Educ., 1957, 34, 330.
  15. R. G. Bates, Crit. Rev. Anal. Chem., 1981, 10, 247 Search PubMed.
  16. F. G. K. Baucke, R. Naumann and C. Alexander-Weber, Anal. Chem., 1993, 65, 3244 CrossRef CAS.
  17. J. Barbosa and V. Sanz-Nebot, Fresenius' J. Anal. Chem., 1995, 353, 148 CAS.
  18. S. Rondinini, P. R. Mussini and T. Mussini, Pure Appl. Chem., 1987, 59, 1549.
  19. J. Barbosa, D. Barrón, J. L. Beltrán and V. Sanz-Nebot, Anal. Chim. Acta, 1995, 317, 75 CrossRef CAS.
  20. G. Kortum, W. Vogel and K. Andrussow, Dissociation Constants of Organic Acids in Aqueous Solution, IUPAC, Butterworths, London, 1961 Search PubMed.
  21. D. D. Perrin, Dissociation Constants of Inorganic Acids and Bases in Aqueous Solution, IUPAC, Butterworths, London, 1969 Search PubMed.
  22. U. Muinasmaa, C. Rafols, E. Bosch and M. Rosés, Anal. Chim. Acta, 1997, 340, 133 CrossRef CAS.
  23. R. Reynaud, Bull. Chem. Soc. Fr., 1967, 4597 Search PubMed.
  24. J. Barbosa, D. Barrón, E. Bosch and M. Rosés, Anal. Chim. Acta, 1992, 264, 229 CrossRef CAS.
  25. J. Barbosa, D. Barrón, E. Bosch and M. Rosés, Anal. Chim. Acta, 1992, 265, 157 CrossRef CAS.
  26. J. Barbosa and V. Sanz-Nebot, Talanta, 1991, 38, 425 CrossRef CAS.
  27. Y. Marcus, Pure Appl. Chem., 1983, 55, 977 CAS.
  28. Y. Marcus, J. Chem. Soc., Faraday Trans. 1, 1989, 85, 381 RSC.
  29. J. Barbosa and V. Sanz-Nebot, J. Chem. Soc., Faraday Trans., 1994, 90, 3287 RSC.
  30. F. E. Critchfield, J. A. Gibson and J. L. Hall, J. Am. Chem. Soc., 1953, 75, 6044 CrossRef CAS.
  31. J. Barbosa, D. Bartrón, J. L. Beltrán and S. Buti, Talanta, 1998, 45, 817 CrossRef CAS.
  32. J. Barbosa, V. Sanz-Nebot and I. Toro, J. Chromatogr. A, 1996, 725, 249 CrossRef CAS.
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