Isotope Ratio Determination in the Earth and Environmental Sciences: Developments and Applications in 2003

New analytical results are reported for rarely determined elements Be, B, Ge, As, Mo, Rh, Pd, Ag, Cd, In, Sn, Sb, W, Re, Ir, Pt, Au, Tl and Bi in MPI‐DING and USGS (BCR‐2G, BHVO‐2G, BIR‐1G) silicate glasses and the NIST SRM 610‐614 synthetic soda‐lime glasses using 193 nm ArF excimer laser ablation and quadrupole ICP‐MS. The method used involved external calibration against GOR132‐G for Ir and NIST SRM 610 for other elements, internal standardisation using Ca, and ablation with a crater diameter of 160 μm and a pulsed laser repetition rate of 10 Hz. Small amounts of nitrogen (5 ml min−1) were added to the central channel gas of the plasma to improve the limits of detection for most of these elements by a factor of 1.2–2.5 and to reduce the oxide interference level to 0.02% (ThO+/Th+). Under these conditions, the LODs for most of these rarely determined elements were within the range 0.1 to 10 ng g−1. The operating conditions that were required to minimise ICP‐induced fractionation (U+/Th+≈ 1) in the mode without nitrogen were accompanied by a 50–60% reduction in sensitivity for elements such as Ca, Au and Pt. In contrast, ICP‐induced fractionation could be minimised (U+/Th+≈ 1) with no loss of analyte sensitivity in the nitrogen mode. Interferences of CuAr+, ZnAr+, Cd+, Pb2+ and Sn+ on Pd+, Rh+, Cd+ and In+ were corrected. Oxide interferences were not considered due to their lower production rate. Analytical precision, as given by one relative standard deviation (% RSD) was less than 15% for most of the elements present at concentrations greater than 0.1 μg g−1. A significant negative correlation was found between logarithmic concentration and logarithmic RSD, with a correlation coefficient of −0.76. This trend indicates that possible chemical heterogeneities for most of these elements are smaller than the analytical uncertainty. Our results for Be, B, Ge, Sb and W are generally in good agreement with their reference values. In contrast, other elements in many of the reference glasses have only information values, upper limits or even no values, which restrict any detailed evaluation of the accuracy of the determined values. However, concentrations from multiple isotopes of one element analysed in this study showed excellent agreement, which guarantee the quality of our data to a certain extent.

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confidence: 99%

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confidence: 99%

Results for Rarely Determined Elements in MPI‐DING, USGS and NIST SRM Glasses Using Laser Ablation ICP‐MS

Liu

et al. 2009

“…Accurate determination of Nb and Ta is a prerequisite of these investigations. LA-ICP-MS has become one of the most powerful techniques for the in situ determination of chemical and isotopic compositions in geological samples (Jackson et al 1992, Günther et al 1997, Sylvester 2001, Kurosawa et al 2002, Eggins 2003, 2007, Hergt et al 2005, Jacob 2006, Woodhead 2006, Jochum et al 2007. Early limitations of LA-ICP-MS, such as the poor absorption of the laser energy by transparent samples, non-homogeneous energy distribution on the sample surface, limited spatial resolution and fluency related ablation characteristics, have been well studied and considerable progress has been made, particularly with the development of UV-laser ablation systems coupled to sensitive ICP-MS instruments (Jeffries et al 1995, Russo et al 2002, Günther and Hattendorf 2005.…”

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confidence: 99%

Niobium and Tantalum Concentrations in NIST SRM 610 Revisited

Gao

Liu

et al. 2008

Niobium and Ta concentrations in MPI‐DING and USGS (BCR‐2G, BHVO‐2G, BIR‐1G) silicate rock glasses and the NIST SRM 610–614 synthetic soda‐lime glasses were determined by 193 nm ArF excimer laser ablation and quadrupole ICP‐MS. Measured Nb and Ta values of MPI‐DING glasses were found to be consistently lower than the recommended values by about 15% and 25%, respectively, if calibration was undertaken using commonly accepted values of NIST SRM 610 given by Pearce et al. Analytical precision, as given by the 1 s relative standard deviation (% RSD) was less than 10% for Nb and Ta at concentrations higher than 0.1 μg g−1. A significant negative correlation was found between logarithmic concentration and logarithmic RSD, with correlation coefficients of ‐0.94 for Nb and ‐0.96 for Ta. This trend indicates that the analytical precision follows counting statistics and thus most of the measurement uncertainty was analytical in origin and not due to chemical heterogeneities. Large differences between measured and expected Nb and Ta in glasses GOR128‐G and GOR132‐G are likely to have been caused by the high RSDs associated with their very low concentrations. However, this cannot explain the large differences between measured and expected Nb and Ta in other MPI‐DING glasses, since the differences are normally higher than RSD by a factor of 3. Count rates for Nb and Ta, normalised to Ca sensitivity, for the MPI‐DING, USGS and NIST SRM 612–614 glasses were used to construct calibration curves for determining NIST SRM 610 concentrations at crater diameters ranging from 16 (im to 60 μm. The excellent correlation between the Nb/Ca1μgg‐1 signal (Nb represents the Nb signal intensity; Ca1μg g‐1 represents the Ca sensitivity) and Nb concentration, and between the Ta/Ca1μg g‐1 signal (where Ta represents the Ta signal intensity; Ca1μg g‐1 represents the Ca sensitivity) and Ta concentration (R2= 0.9992–1.00) in the various glass matrices suggests that matrix‐dependent fractionation for Nb, Ta and Ca was insignificant under the given instrumental conditions. The results confirm that calibration reference values of Nb and Ta in NIST SRM 610 given by Pearce et al. are about 16% and 28% lower, respectively. We thus propose a revision of the preferred value for Nb from 419.4 ± 57.6 μg g−1 to 485 ± 5 μg g−1 (1 s) and for Ta from 376.6 ± 77.6 μg g−1 to 482 ± 4 μg g−1 (Is) in NIST SRM 610. Using these revised values for external calibration, most of the determined average values of MPI‐DING, USGS and NIST SRM 612–614 reference glasses agree within 3% with the calculated means of reported reference values. Bulk analysis of NIST SRM 610 by standard additions using membrane desolvation ICP‐MS gave Nb = 479 ± 6 μg g−1 (1 s) and Ta = 468 ± 7 μg g−1 (1 s), which agree with the above revised values within 3%.

“…The previous two commentaries in this series (Woodhead , 2006, covering the years 2003 and 2004-2005, examined the changing roles of the benchmark methodology for isotope ratio determination-thermal ionisation mass spectrometry (TIMS)-and the newly emergent multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) instrumentation. In just a few short years it is probably true to say that this drama has now been largely played out and that, as far as is reflected in the literature, MC-ICP-MS technologies have come to dominate the analytical landscape, largely as a result of their comparative ease of use and enormous flexibility.…”

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confidence: 99%

Isotope Ratio Determination in the Earth and Environmental Sciences: Developments and Applications in 2006–2007

Woodhead¹

2008

Self Cite

This review documents developments and applications in the field of isotope ratio determination, as reflected in the literature for the Earth and Environmental Sciences for the years 2006 and 2007. The emphasis is predominantly on applications, reflecting the enormous diversity of problems to which isotopic analysis can now be applied, but viewed in the context of rapid uptake of new analytical technologies and significant new drivers of research output.