By Cory Hinz, Engineering Manager, Asahi Kasei Bioprocess America, Inc.
Liquid chromatography processes typically require dilution or blending of constituents to achieve necessary mobile phase solutions. These solutions can be pre-blended – but inline blending is a more efficient solution and can be accomplished by implementing a few clever control schemes in an automated system.
The simplest configuration is two separate constituent streams blended and then driven through a diaphragm pump to the column; but in order to allow for the greatest control, each stream should be metered by a control valve with equal percentage trim. Equal percentage trim affords a superior resolution at the low end of valve travel. This sensitivity is ideal for any gradient – especially for gradients that have heavily lop-sided flow proportions – so that the low flow constituent can maintain acceptable accuracy.