Enzymic Digestion–High-pressure Homogenization Prior to Slurry Introduction Electrothermal Atomic Absorption Spectrometry for the Determination of Selenium in Plant and Animal Tissues

Abstract

Homogenization, in combination with partial enzymic digestion with a crude protease alone or admixed with lipase or cellulase, was investigated as a means of releasing Se residues from zoological and botanical matrices prior to slurry introduction ETAAS. Preliminary timed trials with two zoological certified reference materials (CRMs), one botanical CRM and one animal feed indicated that Se release became quantitative with 4–8 h of digestion, that homogenization prior to digestion increased the initial rate of analyte release, but that homogenization post-digestion and immediately prior to ETAAS did not significantly improve the precision of replicate digestions. Storage of the crude botanical digests at 4 °C for 5 d resulted in quantitative recoveries of Se from each of the digests. Storage at 4 °C for 10 d of 4 and 8 h lipase/protease digests of six other CRMs resulted in quantitative recoveries of Se unless their certified concentrations were appreciably less than the levels determined in control digests containing the enzyme(s) alone. Apparently, Se residues were transferred virtually quantitatively to the liquid phase of the digested suspension and showed no tendency to segregate during the 10 d of storage. Eight other mixtures of ground plant matter (0.13 ≤ [Se] ≤ 1.31 µg g^-1), formulated as animal feed supplements, behaved identically when stored post-digestion. The technique was also applied successfully to freeze-dried fresh and boiled fish tissues The principal advantages of the enzymic digestion procedure are its simplicity and lack of operator intervention.

References

1. I. Novozamski, H. J. van der Lee and V. J. G. Houba, Microchim. Acta, 1995, 119, 183.
2. B. Sansoni and V. K. Panday, in Analytical Techniques for Heavy Metals in Biological Fluids, ed. Fachetti, S., Elsevier, Amsterdam, 1983, p. 91.
3. J. Mincwewski, J. Chwastowska and R. Dybczynski, Separation and Preconcentration Methods in Inorganic Trace Analysis, Ellis Horwood, Chichester, 1982.
4. J. Matusiewicz and R. E. Sturgeon, Prog. Anal. Spectrosc., 1989, 12, 21.
5. H. J. Reid, S. Greenfield and T. E. Edmonds, Analyst, 1995, 120, 1543.
6. F. J. Langmyhr, Analyst, 1979, 104, 993.
7. F. J. Langmyhr, Prog. Anal. At. Spectrosc., 1985, 8, 193.
8. N. J. Miller-Ihli, Anal. Chem., 1992, 64, 965A.
9. Z. A. de Benzo, M. Velosa, C. Ceccarelli, M. de la Guardia and A. Salvador, Fresenius' J. Anal. Chem., 1991, 339, 235.
10. C. Bendicho and M. T. C. de Loos-Vollebregt, J. Anal. At. Spectrom., 1991, 6, 353.
11. N. J. Miller-Ihli, Fresenius' J. Anal. Chem., 1993, 345, 482.
12. S. C. Stephen, D. Littlejohn and J. M. Ottaway, Analyst, 1985, 110, 1147.
13. D. D. Thompson and R. J. Allen, At. Spectrosc., 1981, 2, 53.
14. Y. Madrid, M. Bonilla and C. Camara, J. Anal. At. Spectrom., 1989, 4, 167.
15. I. López García, F. Ortiz Sobejano and M. Hernández Córdoba, Analyst, 1991, 116, 517.
16. M. Hoenig and P. V. Hoeyweghen, Anal. Chem., 1986, 58, 2614.
17. D. Albers and R. Sacks, Anal. Chem., 1987, 59, 593.
18. D. L. Tsalev, V. I. Slaveykova and P. B. Mandjunkov, Spectrochim. Acta, Rev., 1990, 13, 225.
19. N. J. Miller-Ihli, J. Anal. Atom. Spectrom., 1989, 4, 295.
20. C. Bendicho and M. T. C. de Loos-Vollebregt, Spectrochim. Acta, Part B, 1990, 45, 679.
21. N. J. Miller-Ihli, J. Anal. At. Spectrom., 1988, 3, 73.
22. S. Lynch and D. Littlejohn, J. Anal. At. Spectrom., 1989, 4, 157.
23. F. Fagioli, S. Landi, C. Locatelli, F. Righini, R. Settimo and R. Magarini, J. Anal. At. Spectrom., 1990, 5, 519.
24. D. L. Hansen and E. T. Bush, Anal. Biochem., 1967, 18, 320.
25. A. J. Jackson, L. M. Michael and H. J. Schumacher, Anal. Chem., 1972, 44, 1064.
26. L. Murthy, E. E. Menden, P. M. Eller and H. G. Petering, Anal. Biochem., 1973, 53, 365.
27. T. Uchida, H. Isoyama, K. Yamada, K. Oguchi, G. Nakagawa, H. Sugie and C. Iida, Anal. Chim. Acta, 1992, 256, 277.
28. B. Dion, M. Ruzbie, F. R. van de Voort, A. A. Ismail and J. S. Blais, Analyst, 1994, 119, 1765.
29. Y. Tan, W. D. Marshall and J.-S. Blais, Analyst, 1996, 121, 483.
30. Y. Tan, J.-S. Blais and W. D. Marshall, Analyst, 1996, 121, 1419.
31. L. Ebdon and H. G. M. Perry, J. Anal. At. Spectrom., 1988, 3, 131.
32. D. Bradshaw and W. Slavin, Spectrochim. Acta Part B, 1989, 44, 1245.
33. D. Wagley, G. Schmiedel, E. Mainka and H. J. Ache, At. Spectrosc., 1989, 10, 106.
34. C. Bendicho and A. Sancho, At. Spectrosc., 1993, 14, 187.
35. C. Cabrera, M. L. Lorenzo and M. C. Lopez, J. AOAC Int., 1995, 78, 1061.
36. I. López-García, P. Viñas, N. Campillo and M. Hernández-Córdoba, J. Agric. Food Chem., 1996, 44, 836.
37. N. Gilon, A. Astruc, M. Astruc and M. Potin-Gautier, Appl. Organomet. Chem., 1995, 9, 623.
38. J. Dedina and D. L. Tsalev, Hydride Generation Atomic Absorption Spectrometry (Chemical Analysis, vol. 130), ed. Wineforder, J. D., and Kolthoff, I. M., Wiley, Chichester, 1995.
39. K. Johansson, X. Luo and A. Olin, Talanta, 1995, 42, 1979.
40. N. J. Miller-Ihli, At. Spectrosc., 1992, 13, 1.
41. D. S. Forsyth and W. D. Marshall, Environ. Sci. Technol., 1986, 20, 1033.