Enhancements for a more reliable single-use pH sensor

Conference Dates

March 20 – 23, 2022


The adoption of single-use bioreactors is increasing in the pharmaceutical process industry. Advantages of single-use technology have resulted in an increasing demand for improved pH sensors in single-use format. Sensors that are fully integrated into a single-use bioreactor bag facilitate the workflow for sensor handling and operation at end-users’ sites, and mitigate the risk of breaching the sterile integrity of single-use bioreactors.

Until now, mainly single-use pH sensor spots or patches based on optical measurement technology have been integrated in single-use process devices. But in recent years, the market for single-use pH sensors has been characterized by an increasing availability of electrochemical glass pH sensors – in principle, a single-use equivalent to the well-established and characterized reusable in-line pH glass sensors that are employed in the industry for process monitoring and control purposes. However, applying this technology for a single-use sensor necessitates meeting the more stringent requirements for single-use process devices, such as a minimum of two years dry storage capacity (shelf life), availability of post-gamma extractables study data, reliable measurement performance after gamma irradiation and dry storage, and maintaining single-use bioreactors' integrity. The last point is very important, because the integration of a glass pH sensor always leads to the release of certain materials of the sensor components into the process media. For example, electrolyte from the sensor’s reference electrode, sensor storage solution or electrode passivation coating material. Furthermore, the risk of glass breakage must be mitigated during single-use bioreactor bag transport, storage and operation. This means that the influence of these factors must be understood and considered in the development phase of single-use pH sensors.

In our contribution, we will discuss and present a single-use pH sensor that was developed to meet these stringent requirements. We will provide:

- How the sensor’s form factor leads to its safe integration into single-use bioreactors.

- How the passivation of the sensor’s reference electrode enables a dry storage period of 30 months.

- Post-gamma measurement characterization data after 30 months' dry storage.

- Material compliance data and results of a post-gamma BPOG extractables study.

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