Kovats retention index

A retention index (plural retention index, also known as a Kovats index ) provides device-independent normalization retention time in gas chromatography. This makes it possible to use data from other laboratories for substance identification.

History

When dealing with the then new method of gas chromatography Ervin Kováts developed in 1958 the system of retention indices. They are regarded as groundbreaking knowledge for the use of gas chromatography as an analytical method. The concept was later refined. M. L. Lee published in 1979 his concept for today's so-called Lee - index for aromatic hydrocarbons.

Kovats index

The Kovats index uses the relationship between carbon content and retention time of a substance in a gas chromatography system in order to obtain a device independent value for the identification of unknown substances.

For isothermal gas chromatography it is described by the following equation:

Where:

Kovats retention time index,   Number of carbon atoms of the first n- alkane   Number of carbon atoms of the second n- alkane   retention time

For temperature- programmed gas chromatography of the Kovats index is described by the following equation:

Where:

Kovats retention time index,   Number of carbon atoms of the first n- alkane   Number of carbon atoms of the second n- alkane   retention time

Lee index

Lees retention time indices are determined in analogy to the Kovats indices for the reference substances benzene, naphthalene, phenanthrene, chrysene and picene.

Sources of retention indices

Retention indices make it possible to use data from other laboratories for substance identification. Sources of retention indices of chemical compounds are NIST Chemistry WebBook and numerous publications such as Goodner (2008) or Ciaznska - Halarewicz et al. (2003)