ACCURATE AND PRECISE DETERMINATION OF ISOTOPIC RATIOS BY MC-ICP-MS: A REVIEW

For many decades the accurate and precise determination of isotope ratios has remained a very strong interest to many researchers due to its important applications in earth, environmental, biological, archeological, and medical sciences. Traditionally;, thermal ionization mass spectrometry (TIMS) has been the technique of choice for achieving the highest accuracy, and precision. However recent developments in multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) have brought a new dimension to this field. In addition to its simple and robust sample introduction, high sample throughput, and high mass resolution, the flat-topped peaks generated by this technique provide for accurate and precise determination of isotope ratios with precision reaching 0.001%, comparable to that achieved with TIMS. These features, its combination with the ability of the ICP source to ionize nearly all elements in the periodic table, have resulted in air increased rise of MC-ICP-MS for such measurements in various sample matrices. To determine accurate and precise isotope ratios with MC-ICP-MS, utmost cart, must be exercised during sample preparation, optimization of the instrument, and mass bias corrections. Unfortunately, there are inconsistencies and errors evident in many MC-ICP-MS publications, including errors in mass bias correction models. This review examines state-of-the-art methodologies presented in the literature for achievement of precise and accurate determinations of isotope ratios by MC-ICP-MS. Some general rules for such accurate and precise measurements are suggested, and calculations of combined uncertainty of the data using a few common mass bias correction models art, outlined. (C) 2009 Crown in the right of Canada. Published by Wiley Periodicals, Inc., Mass Spec Rev 28:990-1011, 2009