The Experts below are selected from a list of 1911 Experts worldwide ranked by ideXlab platform
Claudine H. Stirling - One of the best experts on this subject based on the ideXlab platform.
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High precision Faraday collector MC-ICPMS Thorium Isotope ratio determination
International Journal of Mass Spectrometry, 2005Co-Authors: Emma-kate Potter, Claudine H. Stirling, Morten B. Andersen, Alex N. HallidayAbstract:Abstract Uranium-series dating of carbonate materials requires precise determination of the spike sample Thorium Isotope ratio, 230 Th/ 229 Th. This ratio is commonly measured using ion counting techniques, however the precision of analyses using ion counting devices suffers from beam intensity limitations, drift in multiplier gain and non-linearities in electron multiplier response. Here, we describe the application of multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS) to determine Thorium Isotope ratios at hitherto unattained precision. For the first time, Thorium Isotope analyses were performed using only Faraday collectors coupled to 10 11 Ω feedback resistors in the amplifier system. Spiked Thorium solutions were concentrated to produce 230 Th and 229 Th signal intensities of around 50 mV and 100 mV, respectively (across a 10 11 Ω resistor) and are run at high intensity for a short period of time (∼1 min). These analyses yield a 230 Th/ 229 Th external reproducibility of better than 0.3‰ for ∼25–30 pg of consumed 230 Th. This is a factor of two better than the best published thermal ionisation mass spectrometry (TIMS) and MC-ICPMS techniques for similar sample sizes, and represents up to an order of magnitude improvement over many other established protocols. Combined with new techniques for high precision Faraday measurement of uranium isotopic composition [1] , this permits improvements in the uncertainty of U-series ages to better than 0.1 thousand years (ka) at 100 ka and 1 ka at 300 ka. It should also be possible to resolve events to ∼14 ka at 600 ka. Using these techniques, the U-series dating limit can be extended from 500–600 ka to 800 ka enabling a more detailed study of the frequency of late Pleistocene climate events.
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high precision u series dating of corals from western australia and implications for the timing and duration of the last interglacial
Earth and Planetary Science Letters, 1995Co-Authors: Claudine H. Stirling, Tezer M Esat, Malcolm T Mcculloch, Kurt LambeckAbstract:Abstract U-series ages using methods of thermal ionisation mass spectrometry (TIMS) are reported for Last Interglacial fossil reefs along the stable coastal margin of Western Australia. Thorium Isotope ratios were measured with superior precision using methods of charge collection. High levels of precision in the measurement of both uranium and Thorium Isotopes has reduced the age uncertainty due to analytical errors, excluding the uncertainty in the decay constants, by a factor of four over the precisions reported by many earlier TIMS workers. Uncertainties in δ234U(T), determined from both 230Th/238U and 234U/238U, are also significantly smaller than previously reported, allowing samples which have undergone diagenetic exchange of uranium and Thorium to be more easily identified. Strict criteria were adopted to screen the new Western Australian data. Reliable ages range from 127 to 122 ka. Published TIMS observations from other localities have been assessed using the same strict criteria. When these are combined with glacio-hydro isostatic sea-level models they indicate that the Last Interglacial period occurred from at least 130 to 117 ka. However, these age constraints are largely determined from single data points and need to be verified with additional ages before considering them to be robust estimates for the timing of onset and termination of the Last Interglacial. Globally, the main episode of reef growth appears to be confined to a narrow interval occurring from 127 to 122 ka, in direct agreement with the narrow range in ages obtained from the Western Australian sites. This may indicate that the Last Interglacial was of short duration, extending from 127 to 122 ka only. Alternatively, this interval may reflect a major reef-building event in the middle of a longer duration (130-117 ka) interglacial interval.
A I Saprykin - One of the best experts on this subject based on the ideXlab platform.
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determination of uranium and Thorium Isotope ratios by inductively coupled plasma mass spectrometry
Journal of Analytical Chemistry, 2004Co-Authors: M G Demidova, A I SaprykinAbstract:Measurement conditions were selected and a procedure was proposed for determining the 234U/238U and 230Th/232Th Isotope ratios using an ELEMENT single-channel double-focusing inductively coupled plasma mass spectrometer. The procedure was tested in analyzing bottom sediments from Lake Baikal with the extraction preconcentration of uranium and Thorium. The accuracy of the procedure was verified using certified reference materials and a model solution by comparing the results obtained with the data of α spectrometry.
Kurt Lambeck - One of the best experts on this subject based on the ideXlab platform.
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high precision u series dating of corals from western australia and implications for the timing and duration of the last interglacial
Earth and Planetary Science Letters, 1995Co-Authors: Claudine H. Stirling, Tezer M Esat, Malcolm T Mcculloch, Kurt LambeckAbstract:Abstract U-series ages using methods of thermal ionisation mass spectrometry (TIMS) are reported for Last Interglacial fossil reefs along the stable coastal margin of Western Australia. Thorium Isotope ratios were measured with superior precision using methods of charge collection. High levels of precision in the measurement of both uranium and Thorium Isotopes has reduced the age uncertainty due to analytical errors, excluding the uncertainty in the decay constants, by a factor of four over the precisions reported by many earlier TIMS workers. Uncertainties in δ234U(T), determined from both 230Th/238U and 234U/238U, are also significantly smaller than previously reported, allowing samples which have undergone diagenetic exchange of uranium and Thorium to be more easily identified. Strict criteria were adopted to screen the new Western Australian data. Reliable ages range from 127 to 122 ka. Published TIMS observations from other localities have been assessed using the same strict criteria. When these are combined with glacio-hydro isostatic sea-level models they indicate that the Last Interglacial period occurred from at least 130 to 117 ka. However, these age constraints are largely determined from single data points and need to be verified with additional ages before considering them to be robust estimates for the timing of onset and termination of the Last Interglacial. Globally, the main episode of reef growth appears to be confined to a narrow interval occurring from 127 to 122 ka, in direct agreement with the narrow range in ages obtained from the Western Australian sites. This may indicate that the Last Interglacial was of short duration, extending from 127 to 122 ka only. Alternatively, this interval may reflect a major reef-building event in the middle of a longer duration (130-117 ka) interglacial interval.
J. S. Becker - One of the best experts on this subject based on the ideXlab platform.
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Stability study of Isotope ratio measurements for uranium and Thorium by ICP-QMS
Atomic Spectroscopy, 1999Co-Authors: I. T. Platzner, J. S. Becker, H.-j. DietzeAbstract:Uranium and Thorium Isotope ratios were determined in 1 to 10 μg/L solutions with an inductively coupled plasma quadrupole mass spectrometer (ICP-QMS). The solutions used 235 U/ 238 U had isotopic abundance ratios ranging from 1 to 0.007 and a 230 Th/ 232 Th ratio of 0.2. The analytical procedure comprised several measurements of eight aliquots (each 18 minutes duration) within a period of up to about 20 hours. It was shown that for 5 to 10 μg/L U solutions, with ratios of 235 U/ 238 U as low as 0.07, relative external standard deviations (RESDs) of 0.03-0.05% can be achieved. RESDs of 0.07% and 0.03%, respectively, were obtained for 1 to 3 pg/L Thorium solutions. Uranium isotopic abundances of the CCLU-500 laboratory standard, calculated from measured and corrected ratios, were in excellent agreement with the accepted values. The RESD results for U and Th Isotope ratio measurements are clearly compatible with single-collector thermal ionization mass spectrometry (TIMS). The advantages and disadvantages of ICP-QMS vs. TIMS and the applicability to Isotope dilution mass spectrometry will be discussed briefly.
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precise Isotope ratio measurements for uranium Thorium and plutonium by quadrupole based inductively coupled plasma mass spectrometry
Fresenius Journal of Analytical Chemistry, 1999Co-Authors: J. S. Becker, Hansjoachim DietzeAbstract:Precise long-term measurements of uranium and Thorium Isotope ratios was carried out in 1 μg/L solutions using a quadrupole inductively coupled plasma mass spectrometer (ICP-QMS). The isotopic ratios of uranium (235U/ 238U = 1, 0.02 and 0.00725) were determined using a cross-flow nebulizer (CFN, at solution uptake rate of 1 mL/min) and a low-flow microconcentric nebulizer (MCN, at solution uptake rate of 0.2 mL/min) over 20 h. For 1 μg/L uranium solution (235U/238U = 1) relative external standard deviations (RESDs) of 0.05% and 0.044% using CFN and MCN, respectively, can be achieved. Additional short term Isotope ratio measurements using a direct injection high-efficiency nebulizer (DIHEN) of 1 μg/L uranium solution (235U/238U = 1) at a solution uptake rate of 0.1 mL/min yielded an RSD of 0.06–0.08%. The sensitivity of solution introduction by DIHEN for uranium, Thorium and plutonium (145 MHz/ppm, 150 MHz/ppm and 177 MHz/ppm, respectively) increased significantly compared to CFN and MCN and the solution uptake rate can be reduced to 1 μL/ min in DIHEN-ICP-MS. Isotope ratio measurements at an ultralow concentration level (e.g. determination of 240Pu/ 239Pu Isotope ratio in a 10 ng/L Pu waste solution) were carried out for the characterization of radioactive waste and environmental samples.
R Garciatenorio - One of the best experts on this subject based on the ideXlab platform.
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determination of trace element concentrations and stable lead uranium and Thorium Isotope ratios by quadrupole icp ms in norm and norm polluted sample leachates
Journal of Hazardous Materials, 2012Co-Authors: J L Mas, M Villa, S Hurtado, R GarciatenorioAbstract:This work focuses on the monitoring of the potential pollution in scenarios that involve NORM-related industrial activities (environmental or in-door scenarios). The objective was to develop a method to determine extent and origin of the contamination, suitable for monitoring (i.e. simple, fast and economical) and avoiding the use of too many different instruments. It is presented a radiochemical method that allows the determination of trace element concentrations and 206Pb/207Pb/208Pb, 238U/234U and 232Th/230Th Isotope ratios using a single sample aliquot and a single instrument (ICP-QMS). Eichrom UTEVA® extraction chromatography minicolumns were used to separate uranium and Thorium in sample leachates. Independent ICP-MS determinations of uranium and Thorium Isotope ratios were carried out afterwards. Previously a small aliquot of the leachate was used for the determination of trace element concentrations and lead Isotope ratios. Several radiochemical arrangements were tested to get maximum performances and simplicity of the method. The performances of the method were studied in terms of chemical yields of uranium and Thorium and removal of the potentially interfering elements. The established method was applied to samples from a chemical industry and sediments collected in a NORM-polluted scenario. The results obtained from our method allowed us to infer not only the extent, but also the sources of the contamination in the area.