Measurement of Attogram Quantities of 231Pa in Dissolved and Particulate Fractions of Seawater by Isotope Dilution Thermal Ionization Mass Spectroscopy
详细信息 查看全文
- 作者：Chuan-Chou Shen ; Hai Cheng ; R. Lawrence Edwards ; S. Bradley Moran ; Henrietta N. Edmonds ; John A. Hoff ; and Rebecca B. Thomas
- 刊名：Analytical Chemistry
- 出版年：2003
- 出版时间：March 1, 2003
- 年：2003
- 卷：75
- 期：5
- 页码：1075 - 1079
- 全文大小：85K
- 年卷期：v.75,no.5(March 1, 2003)
- ISSN：1520-6882
文摘
A technique has been developed to quantify ultratrace231Pa (50-2000 ag; 1 ag = 10-18 g) concentrations inseawater using isotope-dilution thermal ionization massspectrometry (TIMS). The method is a modification of aprocess developed by Pickett et al. (Pickett, D. A.;Murrell, M. T.; Williams, R. W. Anal. Chem. 1994, 66,1044-1049) and extends the technique to very low levelsof protactinium. The procedural blank is 16 ± 15 ag (2
),and the ionization efficiency (ions generated/atom loaded)approaches 0.5%. Measurement time is <1 h. The amountof 231Pa needed to produce 231Pa data with an uncertaintyof ±4-12% is 100-1000 ag (~3 × 105 to 3 × 106atoms). Replicate measurements made on known standards and seawater samples demonstrate that the analytical precision approximates that expected from countingstatistics and that, based on detection limits of 38 and49 ag, protactinium can be detected in a minimum samplesize of surface seawater of ~2 L for suspended particulatematter and <0.1 L for filtered (<0.4 
m) seawater,respectively. The concentration of 231Pa (tens of attogramsper liter) can be determined with an uncertainty of ±5-10% (2) for suspended particulate matter filtered from5 to 10 L of seawater. For the dissolved fraction, 0.5-1L of seawater yields 231Pa measurements with a precisionof 1-10%. Sample size requirements are orders ofmagnitude less than traditional decay-counting techniquesand significantly less than previously reported ICP-MStechniques. Our technique can also be applied to otherenvironmental samples, including cave waters, rivers, andigneous rocks.
),and the ionization efficiency (ions generated/atom loaded)approaches 0.5%. Measurement time is <1 h. The amountof 231Pa needed to produce 231Pa data with an uncertaintyof ±4-12% is 100-1000 ag (~3 × 105 to 3 × 106atoms). Replicate measurements made on known standards and seawater samples demonstrate that the analytical precision approximates that expected from countingstatistics and that, based on detection limits of 38 and49 ag, protactinium can be detected in a minimum samplesize of surface seawater of ~2 L for suspended particulatematter and <0.1 L for filtered (<0.4 m) seawater,respectively. The concentration of 231Pa (tens of attogramsper liter) can be determined with an uncertainty of ±5-10% (2) for suspended particulate matter filtered from5 to 10 L of seawater. For the dissolved fraction, 0.5-1L of seawater yields 231Pa measurements with a precisionof 1-10%. Sample size requirements are orders ofmagnitude less than traditional decay-counting techniquesand significantly less than previously reported ICP-MStechniques. Our technique can also be applied to otherenvironmental samples, including cave waters, rivers, andigneous rocks.