Recent developments in isotope analysis by advanced mass spectrometric techniques - Plenary lecture

An outstanding feature of mass spectrometry is the possibility of determining exact masses and accurate abundances of stable and unstable isotopes with high precision. The importance of isotope ratio measurements by mass spectrometry has grown in the last few years due to a significant improvement of instrumentation with respect to sensitivity, detection limits, precision and accuracy, whereby especially the determination of very small abundances of stable isotopes and radionuclides at the ultratrace concentration level is of increasing importance. The improvement of mass spectrometers for isotope ratio measurements with respect to more efficient and powerful ionization techniques, improved ion separation systems and especially the development of sensitive ion detectors using single ion and multiple ion collectors with increased abundance sensitivity has been accelerated by the necessity of obtaining the most precise and accurate isotope ratio data from the smallest possible amount of sample. Advancement in the determination of stable isotopes and long-lived radionuclides at very low concentration levels and low abundances has been achieved for environmental monitoring, the study of isotope variation in nature and in environmental science, in geoscience (geochemistry and geochronology), cosmochemistry and planetary science and in nuclear science ( for the quality assurance of fuel material and for radioactive waste control) etc. Important progress has been obtained in the refinement of the variable multiple collector system in MC-ICP-MS, improvements in current amplifier technology to achieve ultimate precision and accuracy, increased abundance sensitivity, improved ion optics using zoom optics, enlarged geometry of mass spectrometers and increased signal to noise ratios. This review focuses on methodological and instrumental developments, novel approaches and different applications in isotope ratio measurements using different mass spectrometric techniques such as ICP-MS ( inductively coupled plasma mass spectrometry) and LA-ICP-MS ( laser ablation ICP-MS) versus TIMS ( thermal ionization mass spectrometry), AMS ( accelerator mass spectrometry), RIMS ( resonance ionization mass spectrometry) SIMS ( secondary ion mass spectrometry) and GDMS ( glow discharge mass spectrometry). This review can be regarded as a follow-up to a previous review by the author on a similar topic: J. S. Becker, J. Anal. At. Spectrom., 2002, 17, 1172 ( ref. 2).