Pressure measurements, bioprocessing

In bioprocessing, gas-phase pressure measurements are utilized for evaluation of the partial pressures of various gaseous components, to monitor the performance of outlet gas filters, and to control sterilization procedures. Since they are compatible with the aseptic requirements of biotechnological processes, membrane-type pressure sensors are most commonly used. 

Continuous and detailed knowledge of process conditions is necessary for the control and optimization of bioprocessing operations. Because of containment and contamination problems, this knowledge must often be obtained without sampling the process stream. At present, conditions such as temperatme, pressure, and acidity (pH) can be measured rapidly and accurately. It is more difficult to monitor the concentrations of the chemical species in the reaction medium, to say nothing of monitoring the cell density and intracellular concentrations of hundreds of compounds. 

NCE has also been used to determine various bioprocesses, generally performed by measuring fundamental physical and chemical parameters, such as temperature, pressure, pH, and reaction rates. NCE has also been used to study some chemical reactions on chip followed by the separation of reaction products. 

Thermal Mass Flowmeters The trend in the chemical process industries is toward increased usage of mass flowmeters that are independent of changes in pressure, temperature, viscosity, and density. Thermal mass meters are widely used in semiconductor manufacturing and in bioprocessing for control of low flow rates (called mass flow controllers, or MFCs). MFCs measure the heat loss from a heated element, which varies with flow rate, with an accuracy of 1 percent. Capacitance probes measure the dielectric constant of the fluid and are useful for flow measurements of slurries and other two-phase flows. 

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