AbstractThe resolution power of gel permeation chromatography (GPC) columns and their combinations is tested as a function of the pore sizes of the gels and as a function of the elution velocity. The efficiency of GPC is characterized by the ratioUG/UT, whereUGis the experimental, andUTthe theoretical, inhomogeneity. The latter quantity is obtained from absolute measurements ofMw, andMn. The ratio passes through a minimum for a series of columns with increasing pore sizes. The minimum occurs at that column or column set which is best suited to resolving a given polymer.UG/UTfor any column decreases with decreasing elution velocity. At a certain velocityUG/UTbecomes 1. This velocity is usually smaller thanv= 1 ml./min., but for some columns appreciably greater. Columns with lowUG/UTvalues allow an unexpectedly good separation of mixtures of two polymers withMw/Mn= 2 andMw(I)/Mw(II) = 2. A compression effect toward the peaks of the two components is observed.