Selectivity and Specifity

Specifity describes the ability of a method to detect and identify a single substance or class of substances in a sample without interference or distortion by other components contained in the sample.

A selective methods yields directly interpretable results for all analytes under investigation, while a specific method delivers directly interpretable results for a single analyte, despite the other analytes exhibit mutual interference.

If there are doubts about the selectivity/specifity we have two principal methods to check it. We can either apply an analytic method which delivers a higher information density (for example, GC/MS instead of GC/FID), or we add potentially interfering matrix components and watch the effect on the measured signal. In the second case, it is usually necessary to add interfering components at various concentrations in order to be able to estimate the concentration range where the analytic method delivers valid and reliable results.