Recently, Temperature@lert conducted a test of two separate buffer substances. Buffer vials are effective for ensuring the accuracy of a temperature sensor. This is important for sensitive vaccines and other substances that must be contained within certain temperatures, as per standard procedure or CDC direction. The test was conducted to determine which substance was affected more by external and internal microclimate factors.
For our clients that use buffer vials, temperature sensor accuracy is extremely important. Some of our clients use buffer vials for pharmaceutical and biological applications, such as using temperature sensors to indicate the relative temperature of vaccines and medicine. CDC has a chart that indicates specific temperature information for specific vaccines.
With these specifics in mind, the Temperature@lert "Glycol vs Sand" comparison shows the relative effectiveness of the buffer substances alongside a naked sensor. The importance is accuracy, since appropriate storage temperatures are very precise (range of 6 degrees). A good buffer vial will not allow changes outside this 6 degrees range.
Ideally, for temperature monitoring, this graph would look flat. The temperature would stay the same throughout the tests, with no peaks or valleys to represent change. But 'flatlining' is highly unlikely for any sensor, and might instead represent a flawed system/sensor. From the tests that we've conducted, there are some very simple observations to make. Primarily, it's obvious that the naked temperature sensor fluctuated significantly throughout the test, particularly during automated cycles (defrosting, etc).
More importantly, we see that the sand and Propylene Glycol are relatively similar in their fluctuation. During automation both buffers showed incremental changes in temperature. This is the ultimate goal; implement buffer substances as a shield to protect against minute and brief temperature changes. But which is more accurate? Which has more relevancy to practical application?
The answer: While sand is an excellent and inexpensive buffer substance (2-3 degree fluctuation), the Propylene Glycol gives slightly more accurate readings. The closer look at the Refrigerator chart gives some insight. The Propylene is accurate within 1 degree, and appears to be less affected by the microclimate. The higher level of accuracy and lower rate of change is desirable for vaccine storage, as seen in the strict temperature guidelines. Still, neither substance shows unacceptable variation (over 6 degrees), and both are appropriate for sensitive application.
As one might guess, we discourage the use of naked sensors in these environments, since our tests have shown their variation to be over 6 degrees on average. For biopharmaceutical applications, we consider changes of 6 degrees or less to be the "threshold" for sensor accuracy.
One advantage of sand is that despite the slightly lower level of accuracy, it's less expensive and can be easily transported. As a liquid, Glycol can be difficult to ship and can spill on your other sensors and/or products. Of course we can ship unfilled buffer vials without sand for you to use with glycol.
For Temperature@lert, our sand buffer vials hit a triumvirate of accuracy, cost-effectiveness, and handling simplicity. For the sake of our customers, these concepts are a huge part of our philosophy: smart, simple, and affordable.