The number of theoretical plates (N), is one index used to determine the performance and effectiveness of columns.They are an indirect measure of peak width for a peak at a specific retention time. The number of theoretical plates can be calculated: N=16(tR /W)2 , with tR= retention time and W= peak width. Column efficiency is a function of the column dimensions, its flow rate and the compound and its retention. For column comparison purposes, the number of theoretical plates per meter (N/m) is often used.
