# Plate Theory and Extensions - The Maximum Sample Volume that Can Be Placed on a Chromatographic Column > Page 69

The acceptable
extent to which the performance of the column is denigrated is an arbitrary
decision. In 1957 Klinkenberg (18) recommended that the maximum extra-column
dispersion that should be tolerated without serious loss in resolution was a 5%
increase of the standard deviation (*ca.* 10% increase in peak variance).
This criterion, recommended by Klinkenberg as
the limit for extra-column dispersion, is now generally accepted.

The variance
of a rectangular distribution of sample volume (V_{1}) is _{}. If it is assumed that the peak width
can be increased by 5% as a result of the dispersing effect of the sample
volume, then applying the principle of the summation the variances,

where, from the plate theory, dispersion due to the column alone is

Thus,

Consequently,

_{ }

or

Recalling that _{, }

then,
_{ .
(60)}

_{The
maximum sample volume that can be used without seriously denigrating the column
performance can be calculated using equation (60) from the retention volume of
the solute and the column efficiency. In any separation, there will be one pair
of solutes that are eluted closest together and it is the retention volume of
the first of these that is employed in equation (60) to calculate the maximum
acceptable sample volume.}