In the highly regulated biotech and pharmaceutical industries, effective analytical measurement is critical to ensure high production quality and operational efficiency, while meeting hygienic standards. One key measurement application is conductivity analysis in clean-in-place (CIP) processes. Conductivity measurement is so integral to the pharmaceutical manufacturing process that it is easy to take for granted. However, understanding some basics of its operation and correct application can make a big difference in the effectiveness and efficiency of CIP.
Conductivity in CIP
The CIP process ensures that equipment is cleaned and maintained to minimize any possible cross-contamination and improve safety and product quality. Conductivity analysis is a measure of how well a solution conducts electricity. Cleaning solutions are more conductive than water used for flushing the system, so conductivity measurement enables plants to monitor cleaning steps and final rinse to ensure completeness.
Conductivity sensors can either be calibrated against a solution of known conductivity or against a previously calibrated sensor and analyzer. Typically, the sensor should be calibrated at a point near the midpoint of the operating range as calibration changes the cell constant. To calibrate against a standard solution, the sensor is placed in the standard and the analyzer reading is adjusted to match the known conductivity. To eliminate temperature-related errors, it is important to disable temperature compensation and calibrate using the conductivity of the standard at the measurement temperature. Conductivity standards are susceptible to contamination from atmospheric carbon dioxide. Carbon dioxide dissolves in water forming carbonic acid and increasing the conductivity by as much as 1.5 μS/cm. To minimize contamination errors, it is important to avoid using standards with conductivity less than about 150 μS/cm.
To calibrate against a referee sensor and analyzer, let the process liquid flow through the sensors connected in a series and adjust the process reading to match the referee analyzer. Turning off temperature compensation in both analyzers eliminates temperature compensation errors. To ensure the temperature is the same at both sensors, it is important to keep the sample flow high and tubing runs short. Plants should use clean interconnecting tubing to avoid contamination. Because the system is protected from atmospheric contamination, the method is ideal for calibrating sensors used to measure low conductivity samples.
The CIP process is critical for safety, productivity, and compliance, and understanding conductivity measurement, technology, and best practices is key to improving efficiency and effectiveness. APBN