A new method was designed and used for determining the half-life of the isotope 10 Be. The method is based on (1) accurate 10 Be/ 9 Be measurements of 9 Be-spiked solutions of a 10 Be-rich master solution using multicollector ICP mass spectrometry (MC-ICP-MS) and (2) liquid scintillation counting (LSC) using the CIEMAT/NIST method for determining the activity concentrations of the solutions whose 10 Be concentrations were determined by mass spectrometry. Important requirements for the success of this approach (a) was the previous coating of glass ampoules filled for counting experiments with 9 Be, thereby reducing the risk of the adsorptive loss of 10 Be; (b) the removal of Boron from solutions to be measured by MC-ICP-MS by cation chromatography without the introduction of mass fractionation and (c) the accurate determination of the mass bias of 10 Be/ 9 Be measurements by ICP-MS which are always affected by the space-charge effect. The mass bias factor was determined to be 1.1862 ± 0.071 for 10 Be/ 9 Be from careful fitting and error propagation of ratios of measured Li, B, Si, Cr, Fe, Cu, Sr, Nd, Hf, Tl and U standard solutions of known composition under the same measurement conditions. Employing this factor, an absolute 10 Be/ 9 Be ratio of 1.464 ± 0.014 was determined for a first dilution of the 10 Be-rich master solution. This solution is now available as an absolute Be ratio standard in AMS measurements. Finally, a half-life of (1.386 ± 0.016) My (standard uncertainty) was calculated. This value is much more precise than previous estimates and was derived from a fully independent set of experiments. In a parallel, fully independent study using the same master solution, Korschinek et al. [35] have determined a half-life of (1.388 ± 0.018) My. The combined half-life and uncertainty amounts to (1.387 ± 0.012) My. We suggest the use of this value in nuclear studies and in studies that make use of cosmogenic 10 Be in environmental and geologic samples.

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Determination of the 10Be half-life by multicollector ICP-MS and liquid scintillation counting

This chapter is devoted to the analytical methods employed for making high precision isotope ratio measurements that preserve naturally occurring mass-dependent isotopic variations. The biggest challenge in making these types of measurements is deconvolving mass-dependent isotopic fractionation produced in the laboratory and mass spectrometer, from naturally occurring mass-dependent isotopic fractionation, because the patterns of isotope variation produced by these processes are identical. Therefore, the main theme of this chapter is the description and mathematical treatment of mass-dependent isotopic variations and the possible pitfalls in deconvolving instrumental mass bias from naturally occurring mass-dependent isotopic variations. This chapter will not attempt to catalog methods for isotopic analysis of different elements. These details are better discussed in later chapters where ‘element specific’ analytical issues are covered. Rather, the effort in the chapter will be to focus on those specific items that make mass analysis of non-traditional isotopes challenging and unique, and the methods that can be employed to make precise and accurate isotope ratios.

Isotopic analysis of non-traditional isotopes is made using three main types of mass spectrometers. Elements that can easily be introduced as gases, such as Cl or Br, are typically analyzed using a gas source mass spectrometer. In contrast, metal elements are analyzed using either a thermalionization mass spectrometer (TIMS) or a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS). The main difference between these three types of instruments is how the sample is introduced into the instrument, and how the sample is ionized. In contrast, the analyzer part of each instrument is similar. All three types of instruments use a stack of lenses with variable potential to focus the ion beam, a magnet to resolve the ion beam into different masses, and a series of collectors to measure ion currents of different isotopes simultaneously. The core of the mass analyzer …

Analytical Methods for Non-Traditional Isotopes

Interferences in inductively coupled plasma mass spectrometry. A review

Precise and accurate isotope ratio measurements are an 
important task in many applications such as isotope dilution 
mass spectrometry, bioavailability studies or the determination 
of isotope variations in geological and cosmic samples. There 
is much more interest in ICP-MS for isotope ratio 
determinations at present compared with GDMS, which is 
preferred for the direct measurement of the isotopic 
composition of metallic solid samples. Spectroscopic 
interferences and a limited abundance sensitivity can influence 
the accuracy of isotope ratio determinations by GDMS and 
ICP-MS. In addition, in ICP-MS the space charge effect 
always influences the accuracy and a nozzle separation effect 
may also contribute to the total mass bias. Using a quadrupole 
ICP-MS the mass discrimination per mass unit can be >10% 
for elements with mass numbers <10, about 1–5% for mass 
numbers in the range of 20–120 and only <1% for heavier 
elements. Mass discrimination is strongly dependent on the 
potential of the different lenses of the ion optics and on the 
nebulizer gas flow. Even in magnetic sector field ICP-MS 
instruments a distinct mass discrimination is observed. 
Different procedures such as calibration by substances of 
consistent natural isotopic composition of the same or a 
neighbouring element and by isotopic standard reference 
materials, respectively, in combination with various 
mathematical functions, linear and exponential ones, are used 
for mass bias correction. In addition to the ion counting 
statistics, stability of the ion current is one of the most 
important topics which influences the precision of isotope ratio 
determinations. Magnetic sector field instruments, producing 
flat topped peak shapes, coupled with a multi-collector system 
for simultaneous measurement of different isotopes achieve the 
best relative standard deviation in the range of typically 
0.005–0.02%, which is only comparable with precisions 
obtained by TIMS. However, ICP-TOFMS also has the 
potential for similar results. Typical relative standard 
deviations for other types of plasma source mass spectrometers 
for isotope ratio determinations are as follows: GDMS 0.1–1, 
quadrupole ICP-MS 0.1–0.5, and high resolution ICP-MS 
0.05–0.2%.

Precision and accuracy in isotope ratio measurements by plasma source mass spectrometry

Inductively coupled plasma mass spectrometry (ICP-MS) is an analytical technique that can be used to measure elements at trace levels in biological fluids. Although older techniques such as atomic absorption and atomic emission are still in use by some laboratories, there has been a slow shift toward ICP-MS, particularly in the last decade. As this shift is likely to continue, clinical scientists should be aware of the analytical aspects of ICP-MS, as well as the potential for both spectroscopic and non-spectroscopic interference, and strategies that can be employed to eliminate or mitigate these issues.

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Kenneth W. Halligan

Papers

Nonspectroscopic interelement interferences in inductively coupled plasma mass spectrometry