in chromatography

A number indicative of column performance, calculated from the following equations
which depend on the selection of the peak width expression:
The value of 5.545 stands for
. These expressions assume a Gaussian (symmetrical) peak. In these expressions the
units for the quantities inside the brackets must be consistent so that their ratio
is dimensionless: i.e. if the numerator is a volume, then peak width must also be
expressed in terms of volume. In former nomenclature the expressions 'number of theoretical plates' or 'theoretical plate number' were used for the same term. For simplification, the present name is suggested.

Source:

PAC, 1993, *65*, 819*
(Nomenclature for chromatography (IUPAC Recommendations 1993))
* on page 847