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Q: How can I reduce the costs and environmental impact of dissolution testing?
One way that you can save money and reduce your carbon footprint is by decreasing the electricity consumption of your dissolution testing. With USP Apparatus 1 and 2 dissolution testers, a conventional water-bath system heats the vessels and the dissolution medium they contain. Bathless instruments can perform as well as or better than conventional water-bath instruments while eliminating the water bath and consuming less electricity. The electricity savings in a dissolution lab could be substantial.
Distek's energy consumption tests have shown that a water-bath dissolution system typically uses at least twice as much energy as a bathless unit. Researchers considered two typical operating scenarios, determining: 1) the time and power consumed when performing a 24-hour dissolution run and 2) the power consumed by the equipment between runs.
When a water-bath dissolution tester is not executing a run, its thermocirculator is typically left running to maintain the heat of the water bath, so it continues to consume energy. Even if you turn off the bath between tests, the tester will use a comparatively large amount of electricity to reheat the several gallons of water in the bath to 37°C. A bathless unit has no such requirement, making it more energy efficient.
Below are the results from power-consumption studies comparing the two typical operating scenarios described above. The studies used a Brutech ECM-1220 energy consumption monitor/logger and included a water-bath tester from Distek, two from Agilent, and one from Teledyne Hanson Research.
During a dissolution run. In this scenario, the researchers heated up the four water-bath dissolution systems, with their vessels in place but with no dissolution medium. The thermocirculator temperature was set to 37°C, and after the temperature of the water reached its set point, 900 milliliters of room-temperature medium were added to the vessels. The time required for the various water-bath systems to reach the set-point temperature ranged from 30 to 55 minutes.
The medium was allowed to heat up, assisted by paddles stirring at 100 rpm. After all the vessels' temperatures reached 37°C ± 0.2°C, the researchers started a 24-hour dissolution run. For the duration of the test, the vessels were kept covered and maintained at a temperature of 37°C.
The researchers also programmed a bathless dissolution unit to run a 24-hour test at 37°C, with paddles stirring at 100 rpm. Because the unit didn't need to heat up a water bath, the researchers filled the vessels with 900 milliliters of room-temperature medium and covered them. Then they initiated the unit's program. The medium required approximately 10 to 12 minutes to preheat and equilibrate. Upon equilibration, the 24-hour program began.
Table 1 shows the energy consumed by the four typical water-bath systems and the bathless unit. On average, the water-bath dissolution systems required twice the power to operate than the bathless system.
TABLE 1. Energy consumed by four typical water-bath systems and a bathless unit during a dissolution run
Between dissolution runs. The first row of Table 1 shows the amount of energy required to reheat the water in the bath. Table 2 shows the amount of power used to maintain the heat in the bath: 1) for a 24-hour period, with no dissolution run in progress and with empty vessels secured into the vessel plate, and 2) for a second 24-hour period, with no dissolution run in progress and without the vessels in place.
TABLE 2. Energy consumed to maintain bath heat with no dissolution run in progress
Some of the variation in power consumption between the different brands of dissolution baths was due to the size of the water bath and the volume of water it held. The higher the water volume, the more energy the bath required.
Another factor that can influence energy consumption is how well the system circulates the water within the water bath. A higher flow rate generally results in a more consistent temperature throughout the bath but may consume more power for the pumping of water.
Lastly, the temperature in the lab itself can influence the efficiency of a water-bath system. When water-bath systems are in a cooler environment, they require more power to maintain the proper temperature.
Degassing dissolution medium
Another way to reduce dissolution costs and preserve an increasingly scarce resource is to eliminate the use of helium sparging in degassing the dissolution medium. Helium costs have been going up dramatically, rising 35 percent in 2019 alone . This can substantially increase the cost of dissolution testing processes that use helium sparging to de-aerate the dissolution medium.
You can eliminate this cost by using a medium preparation system that uses a vacuum to de-aerate the dissolution medium rather than helium sparging. This also eliminates the need for tracking the helium, the empty helium containers, and the corresponding emissions.
As the industry and the global community become increasingly cognizant of the need to conserve scarce resources, bathless dissolution systems and helium-free degassing are obvious choices for the planet and for the bottom line.
Ishai Nir is small molecule products manager, Jeff Seely is vice president of sales and business development, and Sean Gilmore is marketing manager at Distek, North Brunswick, NJ. The company manufactures laboratory testing instruments, including the 2500 Select bathless dissolution system and the ezfill medium preparation system, for the pharmaceutical and biotechnology industries.
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