The Use of Disposable and Non-Disposable pH Sensors in Biopharmaceutical Production

Posted in: Applications, Custom Sensors, Electrodes

Author: Derek Pedley

Date Posted: 09/05/2022


The term “biopharmaceuticals” was coined in the 1980s and refers to pharmaceuticals produced using molecular biology techniques as opposed to synthetic drugs that are the products of chemical processes.

Biopharmaceutical processing systems have traditionally employed stainless steel piping and bioreactors. However, for some years the industry has moved towards single-use production methods which rely on disposable elements such as the bioreactor vessels themselves.

Single-use or disposable bioprocessing equipment is now increasingly being adopted for small scale commercial manufacturing replacing classic fixed stainless steel equipment based bioprocessing facilities. Generally, single-use equipment is composed primarily of plastic components that have been sealed and pre-sterilised with gamma radiation. They frequently have a long shelf life of up to 2 years.

While single-use technology offers several advantages including flexibility, it also introduces new measurement and monitoring challenges that need to be met by sensors designed for these applications.

Monitoring and controlling pH is critical to biopharmaceutical manufacturing to ensure the quality and yield of the final product. Requirements for the pH electrodes used in these single‐use bioreactors are different from those used in conventional stainless steel bioreactors where cleaning and sterilisation of the bioreactors means that the pH electrode must be resistant to these procedures or removed or protected. There are cost implications with these requirements which mean that the pH sensor should have a long lifetime. With single use bioreactors, however, long in use lifetime or resistance to steam and cleaning procedures are less crucial factors but a low sensor cost on a per‐use basis is important as well as a long shelf life.

Potentiometric glass electrodes are the most common pH sensors for bioprocess monitoring and control. They are well established, reliable and robust but are generally too expensive to be disposed of after a single run. Therefore, single‐use glass pH electrodes have been developed that can be pre-sterilised with gamma radiation. There are 2 types that are available – wet or dry stored pH electrodes. The wet storage electrode is kept in its calibration buffer thus providing a one-point calibration capability.

The dry stored electrodes have been developed to be integrated directly into the bioreactor during manufacturing including a gamma irradiation process and can be stored dry. The challenge for these is that they may not be possible to calibrate them until the bioreactor has been set up and where failure is now an expensive result. Some dry stored electrodes are claimed to be pre-calibrated before committing to storage.

Meeting The Needs of The Market

At Sentek, we have been producing electrodes, OEM sensors, and other accessories for over 30 years. As the leading manufacturer of bespoke electrochemical sensors in the UK, we follow all the current trends. We have a wide range of custom sensors including pH electrodes that can be dry stored and biotechnology solutions to suit your needs. Whether you need a pharma pH probe, accessories, or a custom solution to a problem, we will work closely with you to fulfil your needs. Check our website today to view our products online, or contact us about a solution to suit you.

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