pH Measurement in Chromatography

Chromatography is a method in biophysical and pharmaceutical applications that enables the separation, identification, and purification of molecules in a mixture based on their different properties. The production of active pharmaceutical ingredients (API) requires purification to obtain the active ingredients in their purest form. The technique comprises two phases before purification:

  • Stationary phase: A porous solid packed into a glass or open-tube capillary.
  • Mobile phase: An aqueous solution that flows through the stationary phase.

The process implements the test solution containing the focused molecules or proteins to be purified via the stationary phase. The mobile phase works through the stationary phase, allowing the molecules to separate themselves into different batches based on their reactive properties, such as molecular weight and absorption characteristics. One of the primary identifiers for proteins in the chromatographic process is pH affinity. Consequently, molecules react differently to acidic or basic solutions. Because of this, monitoring and controlling pH in chromatography columns is key to achieving successful molecule separation. Due to the precise nature of this process, highly accurate pH sensors are a necessary element of chromatography.

Challenging Aspects of Chromatography:

Chromatography requires extreme precision. The molecular properties of separated compounds and the content of the mobile phase solution are all reactive to certain pH values. Correctly identifying which pH buffers to use for successful purification is critical. Ionized compounds are most reactive to acidic mobile phases. Controlling pH at acidic levels for extended periods can cause drift in measurements and shorten sensor life. Furthermore, manual handling of pH sensors during cleaning and calibration threatens the sterility of the chromatography process.

Automated Solutions for Chromatography:

The Knick cCare system is designed to extend sensor life by providing automatic retraction, cleaning, calibration, and insertion of inline process sensors. cCare systems address sensor performance issues in challenging processes that demand accuracy and consistency.

The system comprises the following components:

Durable Sensors — Fully digital Memosens pH sensor’s like the SE 555 eliminates noise commonly found in traditional analog systems. The electrode is designed for hygienic applications and can withstand CIP & SIP cleaning methods.

Automated Holders — Pneumatic hygienic holders such as the Sensogate WA 130H automatically retracts the pH sensor. It is equipped to allow steam delivery directly into the calibration chamber, ensuring sterilization of the sensor. This maintains a closed system, meeting FDA compliance.

Simplified Controller — The controller is responsible for the delivery of air to drive the pneumatic holder and the application of cleaning and calibration solutions. Can be used directly in hazardous locations. Fully automatic, modular, low-wear, and low-maintenance operation.

Intuitive Transmitter — Central programming and operating unit of the system. Provides diagnostics for the Unical 9000 controller and SE 555 pH electrode. Simple plain text operation and easy setting configuration. Expandable to fieldbus communication and operation with Memosens, digital and analog electrodes.

Customer ROI: Maximum Uptime & Accuracy

Fully Automated Process: The Unical 9000 provides full automation of cleaning, calibrating, sterilization, and retraction of the sensor. This vastly reduces human error due to manual calibrations. The system significantly minimizes sensor replacement costs and process downtime.

Avoid Plant Redesign: Each part of the process analysis equipment easily adapts to the present plant design.

Intuitive Knowledge of Sensor & Process Condition: Memosens technology allows technicians to observe sensor conditions using onboard diagnostics of the cCare system. This provides an additional verification that the sensor is healthy and reading accurately.

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pH Measurement in Chromatography