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Chemistry International
Vol. 24, No. 1
January 2002

 

Highlights from Pure and Applied Chemistry


Selectivity in Analytical Chemistry (IUPAC Recommendations 2001)

by J. Vessman, R.I. Stefan, J.F. van Staden, K. Danzer, W. Lindner, D.T. Burns, A. Fajgelj, and H. Müller
Pure and Applied Chemistry, Vol. 73, No. 8, pp. 1381-1386 (2001)

Selectivity is one of the key properties in analytical chemistry. However, definitions within the framework of IUPAC have been rather vague. In the analytical chemical community there has also been an unfortunate overlap between the terms selectivity and specificity, which has been confusing. As a remedy a project was started in the Analytical Chemistry Division within IUPAC in 1999, which was finalized in Brisbane 2001.

The resulting document states that the term selectivity has evolved in parallel with the development of more sensitive and discriminating methods and that several kinds of interactions are used in the discrimination process.

Selectivity in a method is obtained by the combination of several selectivity generating steps as exemplified by LC-MS-MS (with separation and detection selectivity) and by arrays of sensors, where computational selectivity is introduced.

Selectivity can be expressed in a qualitative manner in many ways, but most importantly, selectivity is something that can be graded in contrast to specificity, which is absolute. On the other hand, a calculation of degree of selectivity is not easy and many attempts have been made. A calculation approach useful to the practicing analyst is therefore still to be desired.

The IUPAC recommendation 2001 states that selectivity should be promoted and specificity discouraged as the latter is incorrect. A method is either specific or not, few, if any methods are specific. From a semantic point of view, the expression that "selectivity is the state or quality of choosing carefully" has been derived.

The recommended definition of Selectivity is: Selectivity refers to the extent to which the method can be used to determine particular analytes in mixtures or matrices without interferences from other components of similar behavior.

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