Microwave Digestion of Plant and Grain Reference Materials in Nitric Acid or a Mixture of Nitric Acid or a Mixture of Nitric Acid and Hydrogen Peroxide for the Determination of Multi-elements by Inductively Coupled Plasma Mass Spectrometry

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SHAOLE WU, XINBANG FENG and ADOLPH WITTMEIER


Abstract

The closed-vessel microwave digestion of four plant standard reference materials (SRMs) and two grain reference materials (RMs) in nitric acid or in a mixture of nitric acid and hydrogen peroxide was explored for the direct determination of 26 elements, Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mo, Ni, Pb, Sb, Se, Sn, Sr, Ti, Tl, Th, U, V and Zn, by ICP-MS. In 2.5 or 5 ml of HNO3 with or without the presence of 2 ml of H2O2, 0.5 g of grain or plant sample was pre-digested overnight at room temperature, then at an elevated temperature of 120–165 °C with a pressure limit of 13.8 bar (200 psi) for 20 min. The presence of H2O2 helped to maintain a higher temperature under the pressure limit and reduced the carbon content in the digestates; but its impurities hampered the ICP-MS analysis for certain elements at low levels. The ICP-MS system was calibrated by the method of external standards prepared in reagent blank solutions with In as the internal standard. Interferences from the sample matrices were eliminated, corrected or reduced by subtracting the blank signals, selecting suitable isotopes and applying the appropriate interference correction equations. Using this method, nearly all of the predigestion spike recoveries for the 26 elements were within 90–110%. For the grain RMs studied including Corn Bran and Wheat Flour, the majority of the recoveries for most elements studied were within 85–115%. For the plant SRMs studied including Pine Needles, Tomato Leaves, Apple Leaves and Peach Leaves, the majority of the recoveries were within 90–115% for the determination of As, B, Ba, Ca, Cd, Cu, Mg, Mn, Mo, Pb, Sr, and Zn, within 70–100% for Al, Co, Cr, Fe, K, Sb and V, but were 40–80% for Ni, Th, Ti and U. The low recoveries were caused by the siliceous materials in these samples which were not decomposed during digestion.


References

  1. K. Shiraishi, Y. Takaku, K. Yoshimizu, Y. Igarashi, K. Masuda, J. F. Mclnroy and G. Tanaka, J. Anal. At. Spectrom., 1991, 6, 335 RSC.
  2. J. Thompson and N. I. Ward, Journal of Micronutrient Analysis., 1989, 6, 85 Search PubMed.
  3. W. T. Buckley and M. Ihnat, Fresenius' J. Anal. Chem., 1993, 345, 217 CrossRef CAS.
  4. S. Munro, L. Ebdon and D. J. McWeeny, J. Anal. At. Spectrom., 1986, 1, 211 RSC.
  5. J. Goossens, T. De Smaele, L. Moens and R. Dams, Fresenius' J. Anal. Chem., 1993, 347, 119 CrossRef CAS.
  6. D. Beauchemin, J. W. McLaren and S. S. Berman, J. Anal. At. Spectrom., 1988, 3, 775 RSC.
  7. T. D. B. Lyon, G. S. Fell, K. McKay and R. D. Scott, J. Anal. At. Spectrom., 1991, 6, 559 RSC.
  8. K. Günther, A. von Bohlen, G. Paprott and R. Klockenkämper, Fresenius' Z. Anal. Chem., 1992, 342, 444 CrossRef.
  9. L. Ebdon, A. S. Fisher, P. J. Worsfold, H. Crews and M. Baxter, J. Anal. At. Spectrom., 1993, 8, 691 RSC.
  10. S. Evans and U. Krähenbühl, Fresenius' Z. Anal. Chem., 1994, 349, 454 CrossRef CAS.
  11. M. Krachler, H. Radner and K. J. Irgolic, Fresenius' Z. Anal. Chem., 1996, 355, 120 CAS.
  12. H. Liu, A. Montaser, S. P. Dolan and R. S. Schwartz, J. Anal. At. Spectrom., 1996, 11, 307 RSC.
  13. D. Amarasiriwardena, A. Krushevska, M. Argentine and R. M. Barnes, Analyst, 1994, 119, 1017 RSC.
  14. A. Krushevska, A. Lásztity, M. Kotrebai and R. M. Barnes, J. Anal. At. Spectrom., 1996, 11, 343 RSC.
  15. K. Subramanian, Spectrochim. Acta, Part B, 1996, 51, 291 CrossRef.
  16. E. S. Beary and P. J. Paulsen, Anal. Chem., 1993, 65, 1602 CrossRef CAS.
  17. R. Pepelnik, A. Prange and R. Niedergesäβ, J. Anal. At. Spectrom., 1994, 9, 1071 RSC.
  18. S. Evans and U. Krähenbühl, J. Anal. At. Spectrom., 1994, 9, 1249 RSC.
  19. H. Matusiewicz, R. E. Sturgeon and S. S. Berman, J. Anal. At. Spectrom., 1989, 4, 323 RSC.
  20. V. E. N. De Brätter, P. Brätter, A. Reincke, G. Schulze, W. O. L. Alvarez and N. Alvarez, J. Anal. At. Spectrom., 1995, 10, 487 RSC.
  21. M. A. Vaughan and G. Horlick, Appl. Spectrosc., 1986, 40, 434 CAS.
  22. S. H. Tan and G. Horlick, Appl. Spectrosc., 1986, 40, 445 CAS.
  23. S. Wu, Y. Zhao, X. Feng and A. Wittmeier, J. Anal. At. Spectrom., 1996, 11, 287 RSC.
  24. R. A. Nadkarni, Anal. Chem., 1984, 56, 2233 CrossRef CAS.
  25. P. Tothill, L. M. Matheson, J. F. Smyth and K. McKay, J. Anal. At. Spectrom., 1990, 5, 619 RSC.
  26. H. Vanhoe, J. Goossens, L. Moens and R. Dams, J. Anal. At. Spectrom., 1994, 9, 177 RSC.
  27. M. A. Vaughan and D. M. Templeton, Appl. Spectros., 1990, 44, 1685 Search PubMed.
  28. Y. Shao and G. Horlick, Appl. Spectros., 1991, 45, 143 Search PubMed.
  29. Compilation of Elemental Concentration Data for NBS Clinical, Biological, Geological, and Environmental Standard Reference Materials, U.S. Department of Commerce, National Bureau of Standards, 1987.
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