Retention Indices

Retention indices can be obtained from capillary GC-MS to provide additional criteria for identification. To overcome variations in column temperature and flow-rate, the retention index procedure of Kovats(1958) is recommended.

A solution of each n-alkane from C16 to C36 is co-injected with the sample and the retention times of the n-alkanes peaks are recorded. The retention time of the peak of interest is also recorded.

Gibberellin
Structural and
Mass Spectral
Information
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A1-A30

A31-A60

A61-A90

A91-A126

The retention index is calculated with the following formulae.

Rt(peak of interest)-Rt(preceding n-alkane) + Cn (preceding n-alkane) =C_x
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Rt(following n-alkane)-RT(preceding n-alkane)

C_x x 100 = Retention index.

Reference

Kovats E (1958) Gas chromatographische Charakteriserung organischer Verbindungen.I.Retentions indices aliphatischer halogenide, alkohole, aldehyde und ketone Helv Chim Acta 41: 1915-1932