A process control system for the fractional precipitation of human plasma proteins

Precipitation is the principal technique used by the blood plasma fractionation industry for the separation and concentration of human proteins for clinical use. Although precipitation has many attractions it is particularly difficult to control and the resultant overshoot of key parameters is responsible for loss of product yield and sometimes quality. Much of this problem is due to the inefficiency of mixing and heat transfer in large bulk volumes of protein solution; hence control is limited by the process design. Therefore we have applied the concept of continuous‐flow processing to scale‐down process volumes, to improve the efficiency of mixing and heat transfer and to allow the opportunity for in‐line monitoring and control of important parameters. Ten years experience with a routine manufacturing process of this type has illustrated the benefits of this approach and has led to the modernisation of the process with replacement of centralised computer control by a microprocessor‐based system.