Retrofitting Batch with Single-Use

While environmentalists rightfully decry the frivolous use of throw-away consumable items, there are applications where the strategic and responsible use of disposable products can reduce energy consumption and avoid other environmental downsides when compared to permanent installations. The pharmaceutical industry is a textbook case-in-point where reusing conventional equipment calls for energy-intensive steam sterilization and extensive use of cleaning chemicals.

Single-Use Technologies (SUTs) are growing in the pharmaceutical industry, and with good reason since a pre-sterilized vessel liner can avoid major cleaning efforts. The challenge, as manufacturers explore these options, is adapting other equipment to the new approach. 

 Michael Francis looks at how users are finding ways to modify analytical instruments to meet the new situation. He talks about it in his article, Retrofitting Batch with Single-Use in the June, 2019, issue of Pharma Manufacturing, making the case for why SUT is growing and addressing the side effects.

Single-Use methods do introduce challenges, however, especially with the integration of measurement instrumentation in the bioreactor. The sensor element portion of an instrument must contact the product via a fitting in the Single-Use bag, so this interface must be carefully evaluated. The instrument’s other main component, the transmitter, is not in contact with the process media and thus remains the same for both traditional and single-use processing methods.

Some sensors are mounted in the bag prior to sterilization with gamma radiation, meaning they must be able to survive the procedure without being damaged or otherwise affected. The fittings or adapters used to mount sensors must fulfill aseptic requirements. Any pre-installed sensor must have a shelf life similar to that of the entire bag assembly which can be harder than it sounds, and pH is a prime example.

Emerson has overcome this problem by developing a unique setup allowing Single-Use Rosemount pH sensors to be stored retracted and wetted within a chamber containing a stable, proprietary buffer delivering a two-year shelf life. This configuration allows the sensor to be tested and calibrated while installed in the dry bag before being placed into production, at which time the sensor can be inserted for product contact. The buffer pH can be used as a calibration standard, and a one-point calibration at batch startup results in accuracy within 0.1 pH.

This pH sensor is Emerson’s Rosemount 550pH Single-Use Sensor for SUT applications. Featuring stability of <0.005 pH change per day enables users to do a one-point calibration at the start of a batch and operate for 30 days without any required maintenance or calibration.

Dissolved oxygen (DO) sensors for SUT aren’t as difficult to adapt since the associated fittings use a permeable oxygen membrane isolating the sensors from direct contact with the process media. The sensor can even be removed while in operation for calibration if necessary. For this purpose, Emerson’s Rosemount 550DW Single-Use DO Sensor Adapter enables placement into a bioreactor Single-Use bag. It can be gamma-irradiated and has a shelf life of two years.

As Emerson has solved these challenges, the possibilities for manufacturers keep improving:

Adopting SUT technologies like bioreactor bags minimizes the need for cleaning, sterilization and the associated expenses for WFI, chemicals, energy and supporting infrastructure. Single-Use also offers newfound flexibility to scale operations up and down. Since many of these processes are automated and all must be monitored, there remains a need for pH and DO instrumentation, which must use installation and calibration methods suitable for this demanding service. Updated instrumentation is now available to maintain the performance and familiar form factors of traditional instruments, but with enhancements to deliver long shelf life while meeting single-use sterility requirements.

You can find more information like this and meet with other people looking at the same kinds of situations in the Emerson Exchange 365 community. It’s a place where you can communicate and exchange information with experts and peers in all sorts of industries around the world. Look for the Life Sciences and Liquid Analytical groups, plus other specialty areas for suggestions and answers.