The capture step is the first process step just downstream of the harvested feedstock. Its primary function is to “capture” the target from solution and separate it from the most dominant impurities. The target is then eluted into a significantly smaller volume of buffer for further downstream processing. A resin is selected which has the best combination of dynamic binding capacity, mass recovery, and retention of the target’s biological activity.

Column dimensions and resin particle sizes tend to be larger in capture steps. The feedstock viscosity, the amount of particulate, and the operational pressure limits of the chromatographic hardware used, determine the most appropriate particle size for a capture step. The more viscous and particulate laden the feedstock, the larger the particle needed to produce a linear velocity suitable for the process throughput objectives.