Exact signal matching method

The Exact signal matching Method for Organic IDMS... 

The greatest accuracy attainable by MS is achieved by Isotope Dilution Mass Spectrometry using an exact signal matching method. Like other SIM techniques, an isotopically labeled internal standard is added gravimetrically to the analyte, prior to extraction from its matrix. The quantity of internal standard is then adjusted, over a number of iterations, such that the signal obtained exactly matches that of... 

Even in those cases where an aiialysis is qualitative, quantitative measures are employed in the processes associated with signal acquisition, data extraction, and data processing. The comparison of, say, a sample s infrared spectrum with a set of standard spectra contained in a pre-recorded database involves some quantitative measure of similarity in order to find and identify the best match. Differences in spectrometer performance, sample preparation methods, and the variability in sample composition due to impurities will all serve to make an exact match extremely unlikely. In quantitative analysis the variability in results may be even more evident. Within-laboratory tests amongst staff and inter-laboratory round-robin exercises often demonstrate the far from perfect nature of practical quantitative analysis. These experiments serve to confirm the need for analysts to appreciate the source of observed differences and to understand how such errors can be treated to obtain meaningful conclusions from the analysis. 

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