A concept described by Martin and Synge. Relates chromatographic separation to the theory of distillation. Length of column relating to this concept is called height equivalent to a theoretical plate. See also HETP. Plates are calculated as N = 16(V_R/w_b)2 = 16 (t_R/w_b)2, where V_R is the retention volume, w_b is the width at the peak base, and t_R is the retention time. See also N.