Flow-injection Potentiometric Detection of Phosphates Using a Metallic Cobalt Wire Ion-selective Electrode

Abstract

Flow-injection potentiometric detection of phosphate has been undertaken using a metallic cobalt wire ion-selective electrode. The electrode response to phosphate was characterised by potential readings of high stability versus a Ag/AgCl reference electrode, and results have shown that the electrode displays high sensitivity and selectivity towards the phosphate ion. The metallic cobalt wire electrode was used for the flow-injection potentiometric detection of phosphate using a 0.04 mol l^-1 potassium hydrogen phthalate carrier at pH 5.0. A linear response with a slope of -38.00 ± 0.5 mV decade^-1 change in phosphate activity was obtained in the range 1.0 × 10^-5–5.0 × 10^-3 mol l^-1, and the detection limit was 1 × 10^-6 mol l^-1. The phosphate electrode described in this paper is robust, simple to use, highly selective, inexpensive and highly stable.

References

1. B. Moss, Ecology of Fresh Waters, Blackwell, Oxford, 1980, p. 248.
2. J. Ruzicka and E. H. Hansen, Flow Injection Analysis, Wiley, New York, 2nd edn., 1988.
3. K. Itaya and M. Ui, Clin. Chim. Acta, 1966, 14, 361.
4. H. Van Belle, Anal. Biochem., 1970, 33, 132.
5. D. T. Burns, D. Chimpalee, N. Chimpalee and S. Ittipornkul, Anal. Chim. Acta, 1991, 254, 197.
6. N. A. Chaniotakis, K. Jurkschat and A. Ruhlemann, Anal. Chim. Acta, 1993, 282, 345.
7. W. Godiker and K. Camman, Anal. Lett., 1980, 2, 1237.
8. S. A. Glazer and M. A. Arnold, Anal. Chem., 1991, 63, 754.
9. I. Novozamsky and W. A. Van Riemsdijk, Anal. Chim. Acta, 1976, 85, 41.
10. N. Conrath, B. Grunding St. Huwel and K. Cammann, Anal. Chim. Acta, 1995, 309, 47.
11. D. Xiao, H. Y. Yuan and R. Q. Yu, Anal. Chem., 1995, 67, 288.
12. J. F. Vanstaden, South African J. Chem., 1993, 46, 14.
13. J. F. Coetzee and C. W. Gardner, Jr., Anal. Chem., 1986, 58, 608.
14. H. Hara and S. Kusu, Anal. Chim. Acta, 1992, 261, 411.
15. T. Tanaka, Fresenius' Z. Anal. Chem., 1985, 320, 278.
16. P. W. Alexander and J. Koopetngrm, Anal. Chim. Acta, 1987, 197, 353.
17. D. E. Davey, D. E. Mulcahy and G. R. O'Connell, Talanta, 1990, 37, 683.
18. P. W. Alexander, M. Trojanowicz and P. R. Haddad, Anal. Lett., 1984, 17, 309.
19. A. E. Martell and R. M. Smith, Critical Stability Constants, Plenum Press, No 1–2, 1977.
20. P. L. Bailey, Analysis with Ion-selective Electrodes, Heyden, London, 1978.