# Liquid Chromatography Detectors - Dispersion in Detector Sensors > Dispersion in Connecting Tubes > Page 5

Thus,
_{}

Now, (H) is
the variance per unit length of the tube but a more useful parameter to the
analyst is the volume variance (s_{v}^{2}). This can be derived using the
relationship predicted by the Plate Theory (see book 6).

_{}

where (Vo) is the volume of the tube

and (l) is the length of the tube

Now _{},
consequently _{}

Thus,
expression for the volume standard deviation (_{})
for tubes of different length is

_{} (1)

Employing equation (1) it is
possible to calculate the value of (_{})
for a range of cylindrical connecting tubes of different radii and different
lengths.