A polypyrrole-coated, piezoelectric sensor for Cr^VI. Preliminary results

Abstract

The piezoresonators of a quartz-crystal microbalance were surface-coated with electropolymerised polypyrrole films. After potentiostatic reduction at –0.9 V, the reduced PPy-coated resonators were allowed to react with solutions containing different concentrations of Cr^VI. Mass changes of the polymer film, originated by ionic transfer during the oxidation reaction of PPy by hexavalent chromium, produced frequency shifts proportional to the concentration of Cr^VI. Also, frequency shifts were obtained by reaction of some antioxidants at oxidised PPy-coated resonators. The observed responses depend on several experimental parameters.

References

1. S. A. Katz and H. Salem, The Biological and Environmental Chemistry of Chromium, VCH, New York, USA, 1994.
2. Chromium in soil: Perspectives in Chemistry, Health, and Environmental Regulation, ed. D. M. Proctor, B. L. Finley, M. A. Harris, D. J. Paustenbach and D. Rabbe, CRC Lewis Publishers, Boca Raton, FL, USA, 1997.
3. G. J. Willems, N. M. Blaton, O. M. Peeters and C. J. De Ranter, Anal. Chim. Acta, 1977, 88, 345.
4. R. Milăcic̆, J. Štupar, N. Kožuh and J. Korošin, Analyst, 1992, 117, 125.
5. N. A. Malakhova, A. V. Chernysheva and K. Z. Brainina, Electroanalysis, 1991, 3, 803.
6. M. J. Marques, A. Salvador, A. E. Morales-Rubio and M. de la Guardia, Fresenius' J. Anal. Chem., 1998, 362, 239.
7. C. Wei, S. German, S. Basak and K. Rajeshwar, J. Electrochem. Soc., 1993, 140, L60.
8. R. Senturchelvan, Y. Wang, S. Basak and K. Rajeshwar, J. Electrochem. Soc., 1996, 143, 44.
9. C. S. C. Bose, S. Basak and K. J. Rajeshwar, Electrochem. Soc., 1992, 96, 9899.
10. J. N. Kaufman, K. K. Kanazawa and G. B. Street, Phys. Rev. Lett., 1984, 53, 2461.
11. C. Ehrenbeck and K. Jüttner, Electrochim. Acta, 1984, 41, 1815.
12. G. G. Guibault and J. M. Jordan, CRC Crit. Rev. Anal. Chem., 1988, 19, 1.
13. M. R. Deakin and D. A. Buttry, Anal. Chem., 1989, 61, 1147A.