The Preparative Approach to Liquid Chromatography

The aim of preparative HPLC is to isolate the maximum amount of a certain product at a desired purity in a minimum of time. Preparative chromatography encompasses a broad range of purification processes, from the isolation of minimal amounts of pure substance for subsequent analytical investigation, all the way up to the continuous production of tons of pure product according to the principle of simulated moving bed (SMB) chromatography on an industrial scale. Analytical and preparative HPLC systems possess in principle a similar design but have completely different system specifications based on the completely different priorities of their separation tasks.

As the process scale increases, the throughput and economic efficiency of the whole process become more decisive factors. Preparative HPLC typically involves working with samples at their maximal concentrations and column loading far above the linear adsorption isotherms required for analytical purposes. Detector selectivity and sensitivity become thereby not only less important parameters, but must also be purposely minimized, requiring flow cells with short path lengths. With higher flow rates, eluent consumption and waste disposal costs become more important, making solvent recycling an essential feature. For many purification and fractionation tasks, the maximum number of fractions possible is not important because only a small number of key substances, if not just one, is targeted. What really counts for such production-scale chromatography is that the peak-triggered fraction collection is performed accurately, delivering fractions of desired purity and allowing collection of large volumes for automated repeated runs.

KNAUER offers HPLC systems for exactly those purification needs. The Prepline preparative HPLC systems have been designed for flow rates of up to 1,000 ml/min and pressure stability up to 400 bar. With a footprint of just 22 x 40 cm (W x D) it requires less space than many analytical HPLC systems. It can be operated either manually or with KNAUER ChromGate® software including its FRC Option for fully automatic control and advanced fraction collection options.