Comparisons of normal elution, coupled-columns, and solvent, flow or temperature programming in liquid chromatography

Abstract

The techniques of solvent programming (gradient elution), temperature programming and flow programming can each be used to advantage in dealing with multicomponent samples which involve a wide range in retention volume values. The previously overlooked technique of coupled-column operation (stationary phase programming) is also useful in this respect. The present paper compares these various techniques on a theoretical basis, showing that resolution per unit time decreases in the order solvent programming (best) > coupled-columns > temperature programming ≈ flow programming > normal elution. Experimental examples with liquid-solid adsorption chromatography verify these conclusions. Only solvent programming is useful for extremely wide range samples, but coupled-columns are shown to have outstanding practical advantages for a large class of other separations, particularly those involving repetitive, high efficiency LC. © Preston Technical Abstracts Company.