# Plate Theory and Extensions - Vacancy Chromatography > Page 76

Let the volume
of sample injected be (V_{i}) ml, then the charge measured in 'plate
volumes' will be (_{}). Similarly, if the volume of mobile
phase passed through the column is (y) ml then that will be equivalent to _{} plate
volumes. Assuming the sample that is injected onto the column contains solute
(S) at a concentration X_{s}^{1,
}then from equation (25), the concentration of this solute (_{})
leaving the (n) th plate in the column will be given by:-

Thus, for a chromatogram of (q) solutes, the elution curve equation will be given by,

. (64)

If pure mobile
phase is injected onto the column, then X_{s}= 0 and equation (26)
becomes