Automated gradient‐elution column chromatography of lipids

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Abstract
An automated gradient‐elution chromatography system was developed specifically for the separation of complex mixtures of naturally occuring lipids obtained from various tissues. It uses silica gel columns with concave gradients of increasing polarity. These gradients offer advantages over the convex type because of the absorptive properties of most lipid classes on silica gel.The entire system is operated automatically once the charge is placed on the column. The flow rate is constant throughout the run and the shape of the gradient is predetermined by selecting known values for three parameters. The selection of the gradient is arbitrary but previous knowledge of the chromatographic behavior of the substances to be separated is useful in determining the shape of the gradient. The entire system is controlled by timers, pumps, and solenoid valves. Details of the construction of the apparatus are described and criteria for the selection of acceptable pumps for organic solvents are discussed.Several examples of the separations obtained with the system are described. While silica gel was used as the adsorbent, there is no reason to believe that other adsorbers cannot be substituted for other application. In addition, column size and elution times can be changed to provide better resolution for the specific problems, greatly broadening the application of liquid column chromatography, particularly in the area of routine quantitative analysis of nonvolatile substances. Nongradient elution can also be performed by this apparatus.