Advances in Isotope Ratio Mass Spectrometry and Required Isotope Reference Materials

Abstract

The article gives a condensed version of the keynote lecture held at the International Mass Spectrometry Conference 2012 in Kyoto. Starting with some examples for isotope research the key requirements for metrologically valid procedures enabling traceable and comparable isotope data are discussed. Of course multi-collector mass spectrometers are required which offer sufficiently high isotope ratio precision for the intended research work. Following this, corrections for mass fractionation/ discrimination, validation of the analytical procedure including chemical sample preparation and complete uncertainty budgets are the most important issues for obtaining a metrologically valid procedure for isotope ratio determination. Only the application of such metrologically valid procedures enables the generation of traceable and comparable isotope data. To realize this suitable isotope and/or δ-reference materials are required, which currently are not sufficiently available for most isotope systems. Boron is given as an example, for which the situation regarding isotope and δ-reference materials is excellent. Boron may therefore serve as prototype for other isotope systems.

Organic Reference Materials for Hydrogen, Carbon, and Nitrogen Stable Isotope-Ratio Measurements: Caffeines, n-Alkanes, Fatty Acid Methyl Esters, Glycines, l-Valines, Polyethylenes, and Oils

“…Semiautomated, economical, and fast stable isotope-ratio analysis (SIRA) in continuous flow mode with online elemental analysis (EA), gas chromatography (GC), or liquid chromatography (LC) interfaced with isotope-ratio mass spectrometry (IRMS) has become a routine and invaluable tool in science and industry, including applications in ecology, (paleo)­environmental research, fossil fuel and biofuel research, food authentication, forensics, medical diagnostics, paleoceanography, archeology, and other fields. − Accurate determinations of relative stable isotope ratios of hydrogen (δ 2 H), carbon (δ 13 C), and nitrogen (δ 15 N) require two-point normalization using at least two isotopic reference materials (RMs, also called standards) with contrasting isotopic compositions to (i) anchor the isotopic scale and (ii) compensate for differences in responses of instruments, which commonly compress isotope−δ scales. − The development of suitable organic stable isotope RMs has not kept pace with the rapid development of analytical continuous flow IRMS methods, forcing many practitioners to resort to a single RM and accept the increased analytical uncertainties that accompany ignorance of the relevant isotope−δ scale compression factor. In order to minimize matrix effects, a standard should be chemically as similar as possible to the unknown sample, and therefore organic RMs should be used to normalize δ values of organic samples.…”

Preparation and characterisation of uranium and plutonium quality control samples for isotope dilution mass spectrometry measurements and uncertainty estimation

“…It can be seen that reducing the uncertainty of IDMS results will, in many cases be limited by the uncertainty of the spikes and isotopic standards for mass fractionation. Further improvement, can be achieved by performing double IDMS, which means additional in-house spike preparation and characterisation [13,40].…”

Evaluation of precision of hydrogen isotopic composition determinations by EA-IRMS, GC-IRMS and Py-GC-IRMS

“…Calibration was performed by injecting gas into the chromatograph inlet. There is no standard for use via the pyrolyzer (Faghihi et al, 2012;Renterghem et al, 2012;Vogl, 2013;Cengiz et al, 2014).…”