Isotope Ratio Analysis of NBS U010 Uranium Standard Using External NBS U500 Mass Fractionation Correction
Introduction The NBS Uranium Standard U010 has been analysed in the STATIC Faraday multi-collection mode. This standard has a large range in isotope abundance and the accuracy and precision of an analysis are a good test of the linearity and noise levels of the Faraday cups. Because Uranium does not have a stable isotope ratio,…
Total evaporation analysis (TE) of 500ng loads of U500 using Phoenix TIMS – Precision and Efficiency.
Zenon Palacz, Isotopx Ltd, Middlewich, Cheshire, UK Introduction Uranium does not have a stable isotope pair that can be used to correct for mass fractionation in a TIMS. Measurements have to be made using external mass fractionation control or by total evaporation of the sample and simultaneous (static) collection of all isotopes. Addition of a…
Measurement of NBS U010, NBL U030a and NBL U050 uranium standards by total evaporation using the Phoenix TIMS.
Zenon Palacz, Isotopx Ltd, Middlewich, Cheshire, UK Introduction Although Uranium lacks a stable isotope pair, a number of external techniques are available to correct for the mass fractionation that occurs during TIMS analysis. The ‘gold standard’ methodology is to add a 233U-236U double spike to the sample and use this to calculate the mass fractionation….
Determination of 234U and 236U in IRMM184 Uranium Standard on the Phoenix Thermal Ionization Mass Spectrometer
Introduction IRMM 184 has an extremely low level of 236U (0.12ppm relative to 238U) and a high quality analysis of this minor isotope requires the use of an ion counting detector equipped with a retarding filter. Application Brief G20111 describes a multi-step analysis routine combining Faraday and Daly ioncounting to measure 234U/238U and in this…
Determination of 234U in IRMM184 Uranium Standard on the Phoenix Thermal Ionization Mass Spectrometer
Introduction High precision measurements of 234U/238U are necessary for U-series applications in geological research. Typically, 234U is a low abundance isotope and must be determined with an ion counting detector whilst 238U is the most abundant isotope and must be determined on a Faraday collector. This note describes the performance of the Phoenix TIMS for…
Introduction Neodymium together with strontium isotope ratio measurements are the benchmark analyses that define the ultimate precision and accuracy of isotope ratio measurements that Thermal Ionization mass spectrometers are capable of. The mass fractionation which occurs during thermal ionization can be compensated for using the exponential mass fractionation law. This can lead to single analysis…
Introduction Very high precision Strontium isotope ratio measurements are particularly important in some geochronological applications. For example, variations as small as 0.00001 in 87Sr/86Sr are significant in high resolution dating of marine carbonates. (e.g. McArthur JM, Howarth RJ, Bailey TR. 2001.). In order to test the capabilities of the Phoenix Thermal Ionisation Mass Spectrometer to…
Introduction High sensitivity Sr isotope ratio measurements using TIMS can be used to evaluate sub millimetre isotope variations in zoned minerals and fluid inclusions. Sample sizes of a few nanograms of Sr are generated and so “every ion counts” to get a precise measurement. In this preliminary study a Phoenix TIMS was used to analyse…
Mass Fractionation behaviour of U isotopes during Thermal Ionization, the potential for mass fractionation correction using double spike
Introduction Until recently it was assumed that the terrestrial 235U/238U was 137.88. However high precision 235U/238U measurements using ICP multi collector mass spectrometers1 as well as double spiked TIMS have shown small variations in 235U/238U at the 1- 2 per mil level. In uranium ores these variations are possibly due to changes in environmental redux…
Introduction The study of Osmium isotopes is an important tool in geochemistry and cosmochemistry (e.g. Shirey and Walker 1998, Brandon et al. 2006, Ravizza and Turekian 1992). Side box 1 provides background on the two Os isotope systems of interest. Whilst 187Os/188Os ratios can vary by several percent, the variation in 186Os/188Os is far smaller…