This presentation describes the technical aspects of scaling up a typical chromatography method.

Chromatography methods come in all shapes and sizes.  The scope of each separation scale must be understood.  

In analytical scale chromatography the emphasis is to acquire as much data as possible from a small amount of unknown material.  Similarly in semi-prep chromatography, the emphasis is to produce small amounts of pure material to be studied by other separation techniques or assays, therefore the scope remains the acquisition of data.

In Preparative Scale Chromatography the process stream is well characterized and the emphasis shifts towards the purification of large amounts of material.  Chromatographic parameters are adjusted to maximize the amount of product per unit of time.  Pilot Scale and Process Scale Separations operate under the same scope, generating increasingly larger amounts of product while operating under cGMP guidelines.

All chromatography separations are affected by parameters such as Resolution, Throughput, and Load.  In order to scale up a separation, one must understand how these parameters affect each other.  To scale up a separation , one must start with a method optimized for maximum resolution, then trade some of the resolution for loading capacity until a minimum acceptable resolution at maximum load is reached.   The initial method must be run at optimum flowrate and with the same chromatographic media as one will use in the larger column.

Not all chromatography methods are scalable if one takes into consideration the process economics. If one is purifying a high value added product such as a recombinant protein for pharmaceutical applications, the return on investment might be sufficient to justify the expense of doing a difficult separation using the latest and most expensive means.  If on the other hand, one is purifying a low value added product such as food additives, the cost of doing a difficult and costly separation will probably outweigh the value of the product.  In the later case, chromatography might not be the answer, and other separation techniques such as recristalization or ultrafiltration might be used instead. 

As mentioned earlier, the scope of Preparative Chromatography is to purify as much product as possible per unit time.  To do so the separation is done under overload conditions.  A loading study is performed to determine how much resolution can be traded for loading capacity while running at optimum flow.  The user must determine what is the minimum resolution acceptable for a separation to occur, then increase the sample load until the maximum load at the pre-determined minimum acceptable resolution is reached.  The resulting loading capacity is a constant independent of the column size.

Volume overload is used when the sample has low solubility in the initial chromatography solvent, so one increases the load by increasing the sample volume while keeping the sample concentration low.  

Concentration overload is used when the sample has good solubility in the initial chromatography solvent.  The sample load is increased by keeping the sample volume constant while increasing the concentration.

Once the loading capacity is known, the scaleup can be easily done by applying the scaleup formula.

As mentioned earlier, the basic scale up steps are:  

1. Using the same packing material, and running at the optimum flowrate for the analytical column, optimize the resolution for the particular separation.

2. Determine the loading capacity by trading resolution for load until a minimum pre-determined resolution value is reached.

3. Use the scale up formula to re-dimension the flow and load for the larger column.

This is a scale up chart derived from data obtained from a typical analytical column (4mm i.d.). Three different flowrates and sample loads are indicated for available column sizes.

Pictured above are 50mm i.d. and 75mm i.d. columns of several lengths for pilot bench scale studies.