Chromatography Forum

HI,
Can somebody explain me what's meant by Kovat's index and Mc Reynold's number?
what is their significance?



regards
morningstar

Do a Google search for additional information.

For a given GC column system, an analyte's polarity, molecular weight, vapor pressure, boiling point and the stationary phase property determine the extent of retention. To systematically express the retention of analyte on a given GC column, a measure called Kovat's Index (or retention index) is defined. Kovat's Index (KI) places the volatility attributes of an analyte on a column in relation to the volatility characteristics of n-alkane series on that column.

See "The Packed Column in Gas Chromatography" by Walter Supina, Copyright 1974 page 58 for definition and more details.

Mc Reynold's Number is a value which is indicative of the polarity or selectivity of a GC phase.

See "The Packed Column in Gas Chromatography" by Walter Supina, Copyright 1974 page 75 for definition and more details.

For GC teaching purposes they may still be significant, but the names Kovat and McReynold rarely pass the lips of practising chromatographers any more in this lab at least.

Several reasons - routine GC/MS, data acquisition systems generally, capillary columns of wide application, temperature programming, better retention time stability, retention time locking are some.

Sometimes for publication purposes you might need to calculate the numbers. I have written software to report Kovats indices in my time. I have even dabbled in polynomial interpolation for temperature programming but that's history now. The reams of tables lie unused. In recent years software control of pressure/flow/temperature enables transfer of column characteristics to other machines or replacement columns.

Kovats indecies are still extensively used in the flavours and fragrance industry even with GC/MS. I have never seen them used outside of this industry though.