High accuracy and precision isotope dilution mass spectrometry: An application to the determination of Mo in seawater

被引：0
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作者：
Yang, Lu [1 ]
Sturgeon, Ralph E. [1 ]
机构：
[1] Chemical Metrology, Institute for National Measurement Standards, National Research Council Canada, Ottawa, ON K1A 0R6, Canada
来源：
Journal of Analytical Atomic Spectrometry | 2009年 / 24卷 / 10期
关键词：
Two isotope dilution calibration approaches; a standard two-step and a curve method; were examined in an effort to achieve highest accuracy and precision for determination of Mo in seawater. On-line matrix separation using immobilized 8-hydroxyquinoline permitted transient measurements to be made by both sector field sequential (SF-ICP-MS) and multicollector (MC-ICP-MS) inductively coupled plasma mass spectrometry. Concentrations of 9.42 ± 0.22 and 9.396 ± 0.053 ng g-1 Mo (U; 95% confidence interval; k; 3.18; n = 4) were obtained in NASS-5 seawater using the standard two-step ID method with SF-ICP-MS and MC-ICP-MS; respectively; in good agreement with the certified value of 9.4 ± 1.0 ng g-1 (U; 2; concentration converted from ng ml-1 to ng g -1). A 4-fold enhancement in the precision of determination was evident using MC-ICP-MS. Performance of the standard two-step ID and the ID curve method was also compared following an off-line column separation which permitted steady-state solution nebulization with MC-ICP-MS detection. Undertaking mass bias drift correction during a measurement sequence generated identical concentrations of 9.383 ± 0.016 and 9.383 ± 0.014 ng g-1 Mo (U; n = 4) in NASS-5 using the two-step ID and the ID curve method; despite significant blank correction arising from the off-line column separation which amounted to 4-5% of the total Mo in the sample. Although the ID curve method uses an additional set of reverse ID calibration solutions; it benefits from the advantages of not needing to employ a certified isotopic reference material for mass bias correction or to know isotope abundances of the analyte in the sample; the standard or the enriched spike. An analysis of the sources of uncertainty suggests that the contribution from determination of the ratio is no longer dominant. Further improvements below 0.1% could be achieved by optimizing other sources of uncertainties; such as increasing the masses of enriched spike and natural abundance Mo standard solutions as well as the mass of high purity Mo standard used for its preparation; assuming similar measurement precision for the ratios and the same number of replicate samples measured. © The Royal Society of Chemistry 2009;
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页码：1327 / 1335
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