Page 119 - Illustrated Pocket Dictionary of Chromatography

K

katharometer detector See TCD (thermal conductivity
detector).
kieselguhr See diatomaceous earth.

Knox equation Describes the mathematical relationship between
the reduced plate height, h, and the reduced velocity, v, in a chro-
matographic system:

h = A v 13 + B v + C v

where A, B, and C represent different physical influences on peak
tailing. The practical implication of this equation, and others like it,
e.g., the van Deemter equation, is that they predict a flow rate at which
the smallest h value is obtained (correlates to the largest N value and
greatest efficiency). Unfortunately, this v value is often so slow that it
is impractical for routine separations. The compromise therefore is to
increase throughput (increase v) at the expense of lost efficiency.

Kovat’s retention index, I Used to compare therelative reten-
tion of compounds regardless of column and laboratory through the
use of the following equation:

I = 100 (log V N,x - log V N,n ) (log V N,n - log V N,n )+100n
+1
where V N,x is the retention volume of the analyte, V N,n+1 and V N,n are
the retention volume for two adjacent homologous n-alkanes (e.g.,
n-hexane and n-heptane) that bracket the retention volume of the
analyte, and n is the number of carbons in the alkane.

Illustrated Pocket Dictionary of Chromatography, by Paul C. Sadek.
ISBN 0-471-20021-2 Copyright © 2004 John Wiley & Sons, Inc.
117