Maximum Permissible Extra Column Dispersion
The total
variance of an eluted peak (
)will be the sum of the variance due to column
dispersion (
) and the variance from extra column dispersion (
).
Thus, 
Now, the maximum increase in peak variance from extra column dispersion that can be tolerated while not significantly effecting the resolution is 10 %. This value was suggested by Klinkenberg (3) in 1960 and has been accepted as the criteria for extra column dispersion since that time.
Thus, 
or, 
Substituting for (
) from equation (2), then for an LC column,
(3)
and, 
(4)
Values of 
and 
are included in
table 1. It is seen that the permissible peak widths (taken as (4sv(k'=0)))
are very smalland range from about 1.5 ml for the peak from the microbore column to about 4.8 ml for the 3 mm I.D. and 4.6 mm I.D. columns.
However, it must be noted that these limits are for peaks eluted close to the
dead volume (i.e.,k'=0)where the conditions are most stringent.
