The fundamental conservation-of-mass equation is derived for linear one-dimensional chemical systems in which no lateral diffusion or rate control exists. The theoretical results are applied to (a) a comparison of the fields of chemical separations, thermodynamics, and kinetics; (b) the derivation of a general equation for gradient elution and programmed temperature chromatography; and (c) the description of three new carrier chromato-graphic techniques, carrier magnetochromatography, solid phase carrier electrochromatography, and inverse carrier electrochromatography. The role of chemical equilibria in chromatographic systems is briefly discussed.

A Theory of Chemical Separations: The Fundamental Equation for Ideal Partitioning Separation Systems

Among the various developments in techniques for preparing and purifying materials, chromatographic methods-in which materials to be separated are partitioned between a stationary and mobile phase-occupy an important position; the wide choice of both moving and stationary phases makes possible isolation of physically and chemically related substances from complicated mixtures, isolation which by conventional separation techniques would be ineffective, costly or time consuming. The scientific development of chromatography in general dates back to the work of Tswett in 1906. However, an instance of the use of preparative chromatography may be traced as far back as Biblical times. The book of Exodus recounts that when the people of Israel crossed the Sinai desert and found only water described as bitter, the Lord told Moses to cast a certain tree into the water to make it sweet and drinkable. This may be considered as the earliest record of the use of chromatography for the purification of a material on a rather large scale. In modern times it seems that the impetus to the development of chromatography as a tool in the preparation and purification of materials is due to the recent demand for ultrahigh-purity materials, both organic and inorganic, e.g. the rare earths, transuranic elements, components of biological systems, pharmaceuticals and vitamins. The present review analyzes the potentialities and limitations of the different chromatographic methods, discusses the important operational variables and gives examples of applications and some possibilities of further development, special emphasis being given mainly to the recent and rather explosive developments of gas-chromatography. The criterion of a preparative method in this review is not only its suitability for use on a large scale, but also its applicability to the separation of the material in a highly pure state with a high recovery yield, especially in the case of rare and expensive materials. Thus, the potentialities of chromatographic methods for preparation of organic and inorganic materials analyzed in this review, include also the preparation of minute quantities of materials, e.g. vitamins and radioactive sources.

O. Grubner

Papers

Countercurrent gas-liquid chromatography