Control of conventional chemical manufacturing processes usually involves only a limited number of measurement types, namely temperature, pressure, flow rate, weight and sometimes pH. These readings are then related by the chemical engineer to the chemistry actually taking place through experience with the reaction kinetics. As such, they give indirect measurement of the chemical process. With the production of proteins, and especially with genetically engineered products, there is a much greater need to be able to measure accurately, and on-line if possible, the presence of the desired product in the reacting liquor. This is because of the complexity of the products and the variability of the reactions involved in their production. Such monitoring of the reaction requires sensors other than pressure and temperature. Such control has several benefits. Obviously quality control and assurance are improved and detection of protein contamination during processing is possible. Also data for process modification and development can be acquired during manufacturing runs, and the degree of containment of the process is improved as the amount of manual intervention in the process is reduced.