Isotope-dilution mass spectrometry accuracy

Kingston HMS, Huo D, Lu Y, and Chalk S (1998) Accuracy in spedes analysis spedated isotope dilution mass spectrometry (SIDMS) exemplified by the evaluation of chromium species. Spectrochim Acta 536 299-309. 

Isotope dilution mass spectrometry (IDMS) can be applied with most of the ionisation methods used in mass spectrometry to determine isotope ratios with greater or lesser accuracy. For calibration by means of isotope dilution, an exactly known amount of a spike solution, enriched in an isotope of the element(s) to be determined, is added to an exactly known amount of sample. After isotopic equilibration, the isotope ratio for the mixture is determined mass spectrometrically. The attraction of IDMS is its potential simplicity it relies only on the measurement of ratios. The... 

TI is a very precise and accurate method in stable isotope ratio measurements and quantification of inorganic elements, for example, by isotope dilution mass spectrometry [8]. Because TI is a continuous ion source, it could be coupled to any analyzer that is suitable for such sources. However, because the strength of TI lies in the quantitative precision and accuracy, sector analyzers are preferred to ensure maximum quality. 

Certification using one definitive method. This option is employed when a highly established, internationally accepted scientific primary method is available. The method must be shown to have negligible systematic errors and to provide sufficient measurement accuracy. An example of such a method is isotope dilution mass spectrometry. 

If the reference materials are pure substances and can be specified on the microscopic level, then they represent the unit amount of substance. Because there are no absolute pure substances the representation is in all cases an approximation. The degree of approximation is given by the accuracy of the contents of the main component. In case of pure elements, e.g. metals Fe, Cu, Zn the determination of the main component by coulometry is limited by an uncertainty of 0.01%. The determination of all impurities needs completeness and requires a great deal of analytical equipment. However, a combination of inductively coupled plasma-mass spectrometry (ICP-MS), atomic absorption spectrometry (AAS) and isotope dilution mass spectrometry (ID-MS) covering all elements of the periodic table allows a decrease of total uncertainty to 0.0032% (Cu, see Fig. 8). 

After introducing the reference procedure values for cholesterol, based on IDMS measurements, the different peer group target values have now been replaced by one reference procedure value, which in our case is represented as the exact middle of the screen. The corresponding limits of acceptance are shown as the solid square. As a consequence, methods with inherent systematic errors like the Liebermann-Burchard method and the cholesterol oxidase/iodide method disappeared off the market and today only procedures which are within the limits of acceptance with the reference procedure values established by isotope dilution mass spectrometry exist. In fact, until 1988 there was an unacceptably wide scatter of procedure-dependent target values for many clinical chemical parameters. In order to improve accuracy in clinical chemistry it was absolutely essential to replace these method-dependent target values with reference procedure values. 

Guidelines for achieving high accuracy in isotope dilution mass spectrometry (IDMS). Royal Society of Chemistry, Cambridge, UK... 

Moore LJ, Machlan LA (1972) High accuracy determination of calcium in blood serum by isotope dilution mass spectrometry. Anal Chem 44 2291-2296... 

Bjorkhem, I., Bergman, A., Falk, O., Kallner, A., Lantto, O., Svensson, L., Akerlof, E., and Blomstrand, R. (1981). Accuracy of some routine methods used in clinical chemistry as judged by isotope dilution-mass spectrometry. Clin. Chem. 27, 733-735. 

Studies such as this one allow geoscientists to investigate the past and to get some idea of geological conditions then. Because a small error in the measurement of the ratio translates into a large uncertainty in the calculated age of the sample, isotope dilution mass spectrometry s superior sensitivity and accuracy are important in obtaining meaningful results. 

Isotope dilution mass spectrometry can be used to determine element concentrations at trace and macro levels with high sensitivity and high accuracy Several examples of sensitive and accurate measurements with IDMS are Illustrated in Table I for foodstuffs and biological matrices ( 2 4 >35 >62 >68) The accuracy of IDMS has been used to certify elemental concentrations in a wide variety of matrices with concentrations ranging over eight orders of magnitude ... 

Atomic Absorption Spectrometry Methods The National Committee for Clinical Laboratory Standards (NCCLS) has approved a method using atomic absorption spectrophotometry (AAS) as a reference method for measuring total serum calcium. This method has been compared with isotope dilution-mass spectrometry (ID-MS), the definitive method for total serum calcium developed by the National Institute of Standards and Technology. The reference method is reported to have an accuracy of 100 2%, compared with 100 0.2% for ID-MS. Although AAS can provide better accuracy and precision for total serum calcium than the widely used photometric methods, it is used by only a few laboratories. It should continue to be used for validating new total calcium methods. 

De Bievre, P. (1990). Isotope Dilution Mass Spectrometry what can it do for accuracy in Trace Analysis Fres. Z. Anal. Chem. 337, 766-771. 

GUIDELINES FOR ACHIEVING HIGH ACCURACY IN ISOTOPE DILUTION MASS SPECTROMETRY (IDMS)... 

Guidelines for Achieving High Accuracy in Isotope Dilution Mass Spectrometry... 

---