On-line deoxygenation for reductive electrochemical detection of artemisinin and dihydroartemisinin in liquid chromatography

Abstract

A straightforward method for the deoxygenation of mobile phases and samples required for reductive detection in liquid chromatography is described. The method, which is based on the use of a commercially available on-line deoxygenator placed between the column and the detector, eliminates the problems associated with separate deoxygenations of the mobile phase and samples and restrictions imposed by work in an oxygen-free environment. The method is compatible with determinations of artemisinin and its main metabolite, dihydroartemisinin, and also artelinate, in liquid samples. With the deoxygenator, efficiencies of the order of 4000–10 000 theoretical plates were obtained for artemisinin using 3.0, 4.0 and 4.6 mm diameter columns. The extra-column band broadening due to the deoxygenator was not found to be a limiting factor. Amperometric detection with a gold electrode gave rise to lower background currents and better peak current reproducibilities than that with glassy carbon and gold amalgam electrodes. The relative standard deviations in the peak current for 10 injections of 100 pmol of artemisinin, dihydroartemisinin and artelinate were 3.0, 1.4 and 3.3%, respectively. The peak currents for the compounds depended linearly on the amount injected in the range 10–200 pmol and the detection limits for artemisinin and dihydroartemisinin were calculated to be 2 and 3 pmol, respectively.

References

1. S. M. Lunte, C. E. Lunte and P. T. Kissinger, in Laboratory Techniques in Electroanalytical Chemistry, ed. Kissinger, P. T., and Heineman, W. R., Marcel Dekker, New York, 2nd edn., 1996, ch. 27.
2. H. Gunasingham and B. Fleet, in Electroanalytical Chemistry, ed. Bard, A. J., Marcel Dekker, New York, 1989, vol. 16, p. 89.
3. Z. M. Zhou, J. M. Anders, H. Chung and A. D. Theoharides, J. Chromatogr., 1987, 414, 77.
4. V. Navaratnam, S. M. Mansor, L. K. Chin, M. N. Mordi, M. Asokan and N. K. Nair, J. Chromatogr. B, Biomed. Appl., 1995, 669, 289.
5. K. Lam Chan, K. Hay Yuen, S. Jinadasa, K. Khiang Peh and W. Tuck Toh, Planta Med., 1997, 63, 66.
6. S. D. Yang, L. M. Ma, J. H. Sun and Z. Y. Song, Acta Pharm. Sin., 1985, 20, 457.
7. V. Melendez, J. O. Peggins, T. G. Brewer and A. D. Theoharides, J. Pharm. Sci., 1991, 80, 132.
8. A. D. Theoharides, J. O. Peggins, T. G. Brewer, V. Melendez and J. M. Boyd, LC-GC, 1989, 7, 925.
9. Z.-M. Zhou, Y.-X. Huang, G.-H. Xie, X.-M. Sun, Y.-L. Wang, L.-C. Fu, H.-X. Jiang, X.-B. Guo and G.-Q. Li, J. Liq. Chromatogr., 1988, 11, 1117.
10. D. Dinh Duc, P. J. De Vries, N. Xuan Khan, H. L. Nguyen Binh, P. A. Kager and C. J. van Boxtel, Am. J. Trop. Med. Hyg., 1994, 51, 785.
11. P. A. Kager, M. J. Schultz, E. E. Zijlstra, B. van den Berg and C. J. van Boxtel, Trans. R. Soc. Trop. Med. Hyg., 1994, 88, 53.
12. J. F. S. Ferreira, D. J. Charles, K. Wood, J. Janick and J. E. Simon, Photochem. Anal., 1994, 5, 116.
13. Y. Huang, G. Xie, Z. Zhou, X. Sun and Y. Wang, Biomed. Chromatogr., 1987, 2, 53.
14. J. Karbwang, K. Na-Bangchang, P. Molunto, V. Banmairuroi and K. Congpuong, J. Chromatogr. B, Biomed. Appl., 1997, 690, 259.
15. N. Sandrenan, A. Sioufi, J. Godbillon, C. Netter, M. Donker and C. van Valkenburg, J. Chromatogr. B, Biomed. Appl., 1997, 691, 145.
16. K. C. Zhao and Z. Y. Song, Acta Pharm. Sin., 1993, 28, 342.
17. P. L. Olliaro and P. I. Trigg, Bull. W. H. O., 1994, 75, 565.
18. N. Pras, J. F. Visser, S. Batterman, H. J. Woerdenbag and T. M. Malingre, Phytochem. Anal., 1991, 2, 80.
19. D. L. Klayman, Science, 1985, 228, 1049.
20. Z. Song and K. Zhao, Proc. Chin. Acad. Med. Sci. Peking Union Med. Coll., 1989, 4, 229.
21. Z. M. Zhou, J. C. Anders, H. Chung and A. D. Theoharides, J. Chromatogr., 1987, 414, 77.
22. T. T. Hien and N. J. White, Lancet, 1993, 341, 603.
23. A. D. Theoharides, M. E. Smyth, R. W. Ashmore, J. M. Halverson, Z. M. Zhou, W. E. Ridder and A. J. Lin, Anal. Chem., 1988, 60, 115.
24. G. Edwards, Trans. R. Soc. Trop. Med. Hyg., 1994, 88, Suppl. 1, 37.
25. P. O. Edlund, D. Westerlund, J. Carlqvist, W. B. Liang and J. Yunhua, Acta Pharm. Suec., 1984, 21, 223.
26. N. Acton, D. L. Klayman and I. J. Rollmani, Planta Med., 1985, 51, 445.
27. K. T. Batty, T. M. E. Davis, L. T. Anh Thu, T. Quang Binh, T. Kim Anh and K. F. Ilett, J. Chromatogr. B, Biomed. Appl., 1996, 677, 345.
28. C. Franco and J. Olmsted, Talanta, 1990, 37, 905.
29. J. M. Achord and C. L. Hussey, Anal. Chem., 1980, 52, 601.
30. W. Stumm and J. J. Morgan, Aquatic Chemistry, Wiley, New York, 2nd edn., 1981, p. 44.
31. J. R. Poulsen, K. S. Birks, M. S. Gandelman and J. W. Birks, Chromatographia, 1986, 22, 231.
32. C. F. Poole and S. A. Schuette, Contemporary Practice of Chromatography, Elsevier, New York, 1984, p. 521.
33. H. Lingeman and W. J. M. Underberg, Detection-Oriented Derivatization Techniques in Liquid Chromatography, Marcel Dekker, New York, 1990.
34. F. Zhang, Jr., D. K. Gosser and S. R. Meshnick, Biochem. Pharmacol., 1992, 43, 1805.