The principle of labelling methodologies

The most obvious and ideal method for the determination of the mass concentration of a compound in a mixture would be to totally separate it from all components and weigh it. Unfortunately this can seldom be undertaken, extraction being neither completely selective nor quantitative, indeed impossible if it is in a very low concentration. In this perspective, analytical chromatography of the sample, a separative method par excellence, is an indirect way to achieve extraction and to accomplish this goal. The group of methods described below stem from an entirely different principle. These other approaches are gathered under the 

Chemical Analysis Second Edition Francis and Annick Rouessac 

Several analytical methods have been developed from this principle. An element or a molecule can be labelled as follows  

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