CHROMATOGRAPHY SCALE-DOWN In theory, chromatography is one of the more straightforward unit operations to scale down. Factors at the large scale such as column-header design and packing can be difficult to control and may result in reduced accuracy of the scale-down model. This section presents a review of general guidelines for scaling down.
Use representative feed streams, preferably from full-scale manufacturing. First perform a complete analysis of product concentration, quality attributes, and other feed stream characteristics (such as pH and conductivity) to ensure a good match. If possible, use feed streams from different lots at small scale to learn about the effect of feed stream quality on the performance. In addition, acquire some knowledge of the storage and stability of the feed stream material. Storage-related degradation of the inventory could affect the outcome of the small-scale runs.
Buffers and other solutions should be made up and released by manufacturing. If it is not possible to obtain these, mix solutions with GMP-released raw materials, or material of an equivalent grade from an approved vendor. Follow exactly the solution recipes from manufacturing. The pH, temperature, and conductivity probes that check buffer properties must be comparable with those used at the large scale. Measure pH and conductivity at the same temperature spelled out in the recipe. The pH and conductivity standards should also be comparable (preferably identical) to those used in manufacturing.
Hardware Our experience has been that an automated small-scale chromatography system, such as the äKTA Explorer, excels at small-scale studies. It offers precise, accurate, and reproducible control of flow rates and gradients. However, you still have to check and calibrate the accuracy and precision of in-line detectors (pH, conductivity, temperature) by using off-line probes.