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Conductivity / Resistivity: inherent in water for pharmaceutical use

Elscolab blog article - Conductivity / Resistivity: inherent in water for pharmaceutical use

From natural drinking water to WFI (Water For Injection): conductivity is the first quality parameter.

Follow the water flow in a pharmaceutical or biotech company and you will come across inline or online conductivity measurements: from the incoming drinking water to the purest water used for production. For this industry drinking water is the most important raw material. The conductivity or conductance provides a good indication of its quality at all stages of the purification process until it has reached its purest form.

PAT in water purification

Since 2002, PAT (Process Analytical Technology) has made its way into the pharmaceutical industry through the launch of the FDA initiative: “Pharmaceutical cGMPs (current good manufacturing practices) for the 21st Century: A Risk-Based Approach”. Production of the purest water is pre-eminently a continuous process. Continuous quality monitoring of this process is therefore necessary to meet the FDA’s requirements. Conductivity is one of the key parameters in this. The quality requirements that the water must meet have been determined in the various international pharmacopoeias. For conductivity, USP <645> is the best known. Other pharmacopoeias, including the European (EP), set similar standards.

During the same period, conductivity sensors evolved from classical analogue measuring cells to the digital and intelligent version. The USP has also embraced the benefits of digital sensors. What's more, they’re recommended.

Cleaning and Purging  

Pharmaceutical and biotechnological processes often run in batches. The (bio)reactor is cleaned between two batches or when the product is changed. This cleaning process is also known as CIP (Cleaning In Place).

In essence, a cycle consists of rinsing with water, cleaning with an alkaline and any acidic solution at a high temperature, followed by rinsing with pure water. The transition between the different products can be monitored with a conductivity sensor. The transition between water and acid or base requires a sensor that is suitable for relatively high measuring ranges, while the final rinse with ultra pure water requires a sensor for the very low measuring range.

Digital UniCond sensors mean that it is possible to use one and the same sensor. This prevents confusion or even errors during installation, simplifies start-up and reduces costs for maintenance, validation and spare parts.

Intelligent Conductivity Sensors

The world is or is becoming digital. So also conductivity measurement. Digital sensors are pre-calibrated by the manufacturer (with certificate). This makes the start-up really “Plug & Measure”. The sensor itself digitally keeps the calibration history (Electronic Documentation). In addition, an intelligent sensor (ISM, Intelligent Sensor Management) helps with the “predictive maintenance” concept with built-in indication of the service life (DLI, Dynamic Lifetime Indicator) and remaining time until the next service (TTM, Time to Maintenance). All this results in better understanding of the process and contributes to higher efficiency, reliability, safety and traceability. 

USP sets requirements for the calibration of digital sensors for conductivity. Not only the transmitter, but also the electronics of the sensor must be calibrated. Digital calibrators for ISM sensors meet the requirements set. The entire course can be calibrated without the sensor being removed from the process. Thornton digital calibrators are the only ones on the market that meet the latest edition of the USP. USP obliges calibrating the entire digital measurement circuit independently of the sensor. It can be done!


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