# Plate Theory and Extensions - The Plate Theory > Page 10

for Plate
2,
_{ }

for Plate 3,

and for the nth Plate, (12)

Equation (12) is the basic elution curve equation and is, in fact, a Poisson function. In due course, it will be shown that if (n) is large, the function tends to the normal Error function or Gaussian function. As in most chromatography systems, (n) >>100 most peaks will be Gaussian or nearly Gaussian in shape. However, due to equipment limitations and other factors, the shape of a peak can be distorted which will also be discussed in due course.