Solid-phase reactors as high stability reagent sources in flow analysis: selective flow injection spectrophotometric determination of cysteine in pharmaceutical formulations

Abstract

The flow injection spectrophotometric determination of cysteine was carried out by reaction with cobalt(II) ions entrapped in a polymeric material and filling a packed-bed reactor; the released cobalt(II) complexed with the amino acid was monitored at 360 nm. The method worked with a high repeatability, even with independent reactors, days and solutions. Selectivity of the procedure was tested with twenty different foreign compounds found in pharmaceutical formulations containing cysteine, parent amino acids included; no serious interferences were observed. The calibration graph for cysteine was linear over the range 1–90 µg ml^–1 with a relative standard deviation of 0.8% at 60 µg ml^–1 (n = 158). The calculated sample throughput was 90 h^–1. The method was applied to determine the content of cysteine in pharmaceutical formulations.

References

1. W. F. Pickering, Chem. Anal., 1964, 53, 91.
2. J. V. García Mateo and J. Martínez Calatayud, Chem. Anal. (Warsaw), 1993, 38, 1.
3. J. Martínez Calatayud, Flow Injection Analysis of Pharmaceuticals. Automation in the Laboratory, Taylor and Francis, Cambridge, 1996.
4. J. V. García Mateo and J. Martínez Calatayud, Pharm. Technol. Int., 1992, 4, 17.
5. J. V. García Mateo and J. Martínez Calatayud, Pharm. Technol. Int., 1992, 4, 30.
6. J. V. García Mateo and J. Martínez Calatayud, Anal. Chim. Acta, 1993, 274, 275.
7. L. Lahuerta Zamora, J. V. García Mateo and J. Martínez Calatayud, Anal. Chim. Acta, 1992, 265, 81.
8. L. Lahuerta Zamora and J. Martínez Calatayud, Talanta, 1993, 40, 1067.
9. L. Lahuerta Zamora and J. Martínez Calatayud, Anal. Chim. Acta, 1994, 280, 145.
10. J. L. López Paz and J. Martínez Calatayud, J. Pharm. Biomed. Anal., 1993, 11, 1093.
11. M. Catalá Icardo, L. Lahuerta Zamora and J. Martínez Calatayud, LRA, 1998, 10, 33.
12. A. V. López Gómez, J. V. García Mateo and J. Martínez Calatayud, Analyst, in the press.
13. A. A. Alwarthan and H. A. Al-Lohedan, Talanta, 1994, 41, 225.
14. M. M. Amer, M. F. El-Tarras, S. A. Fattah and F. M. Metwally, Egypt J. Pharm. Sci., 1989, 30, 1.
15. A. K. Sen and T. K. Das, Indian Drugs, 1989, 27, 124.
16. Y. Kumar, Y. K. S. Rathore, S. C. Mathur, N. Murugesan and P. D. Sethi, Indian Drugs, 1992, 29, 416.
17. J. Hernández-Martínez, P. J. Martínez, P. Gutiérrez and M. I. Martínez, Talanta, 1992, 39, 637.
18. A. Besada, Anal. Lett., 1988, 21, 435.
19. P. K. Chatterjee, C. L. Jain and P. D. Sethi, Indian J. Pharm. Sci., 1987, 49, 34.
20. N. Q. Jie, J. H. Yang and Z. G. Zhan, Anal. Lett., 1993, 26, 2283.
21. M. Khodari, A. M. Ali and N. A. El-Maali, Anal. Lett., 1993, 26, 1099.
22. A. MacDonald and T. A. Nieman, Anal. Chem., 1985, 57, 936.
23. A. A. Alwarthan, S. A. Al-Tamrah and A. A. Akel, Anal. Chim. Acta, 1994, 292, 201.
24. F. Feigl, Análisis cualitativo mediante reacciones a la gota. Aplicaciones inorgánicas y orgánicas, Paraninfo, Madrid, 1949. p. 131.
25. H. Willard and S. Kaufmann, Anal. Chem., 1947, 19, 505.
26. W. H. Shipman and J. R. Lai, Anal. Chem., 1956, 28, 1151.
27. S. L. Morgan and S. N. Deming, Anal. Chem., 1974, 46, 1170.
28. J. A. Nelder and R. Mead, Comput. J., 1965, 808.
29. J. Martinez Calatayud and J. V. García Mateo, Recent research developments in pure and applied analytical chemistry, Transworld Research Network, Trivandum, India, in the press.
30. J. Bjerrum, G. Schwarzenbach and L. G. Sillen, Stability constants of metalion complexes, The Chemical Society, London, 1964, p. 348.
31. A. E. Martell and M. Calvin, Chemistry of the Chelate Compounds, Prentice-Hall, Englewood Cliffs, NJ, 1956.
32. British Pharmacopoeia, Her Majesty's Stationery Office, London, 1993.
33. Martindale, The Extra Pharmacopoeia, The Pharmaceutical Press, London, 30th edn. 1993.