Specificity, Selectivity

A part of the aim of method validation is to verify that only the analytes of interest are actually measured. The specificity of a method refers to the extent to which it can unambiguously detect and determine a particular analyte in a mixture, without interference from the other components in the mixture.
In some fields of measurement selectivity is used as an alternative from specificity, i.e. selectivity is the ability of a method to selectively measure an analyte in the presence of other substances. Specificity and selectivity will be enhanced by measuring a unique property, such as absorbance at a specific wavelength and by separating the analyte from other substances present in the sample.