Unleashing the Potential of Virtual Temperature Buffering
Episode 3: Going Beyond Physical Temperature Buffering
Through this series of posts, we have established the need and value for physical temperature buffering is not just important but crucial. The primary objective of this process is to accurately represent the temperature experienced by the contents of the storage unit. Thermal buffering is a key process that helps effectively simulate the thermal properties of the items stored in the refrigerator, providing a more realistic measurement of the temperature conditions experienced by the stored products. [Episode 1]
Understanding the characteristics of the buffer material is the next crucial step. The CDC guidance, a beacon of industry direction, outlines the possible buffer media: glycol, glass beads, sand, and Teflon®. Other mediums observed in use include aluminum and silicone (RTV) forms. The table below contains the specific heat for these buffer materials, providing a comprehensive resource for computing the equivalent size of ethylene glycol to a reference standard.
The CDC guidance notes a probe in a thermal buffered material, providing examples such as glycol, glass beads, sand, and Teflon®. It is appropriate to examine these alternatives to glycol. These options provide an inert material easily administered in the storage unit. Intuitively, one would equate the volume of each of these to the glycol volume it is replacing. From the data in Tables 1 and 2, the properties of each can be compared to the de facto standard glycol, and the characteristics of each can be examined.
Given the data in Table 2 above, the application of a glycol substitute requires serious consideration. The energy density of the substitute material must be carefully considered in relation to the volume of the buffer selected. Improperly sizing the substitute material can result in the same adverse effects as selecting a buffer that is too large.
The CDC guidance does not state how large or small the temperature buffer should be. It does note, however, that its purpose is defined below.
“…a buffered temperature probe, which is the most accurate way to measure actual vaccine temperatures. Temperatures measured by a buffered probe match vaccine temperature more closely than those measured by standard thermometers, which tend instead to reflect air temperature.”
The development team at PharmaWatch™ has innovated a solution that operates at the convergence of accurately representing the stored goods and sufficiently dampening the temperature excursions.
As the requirement to buffer became more pervasive, PharmaWatch™ worked to address the problem in a holistic manner, seeking the optimum solution. From these observations, the PharmaWatch™ team developed the concept of Virtual Temperature Buffering™ (VTB). VTB is an algorithm-based tool incorporating an input of air temperature and scientifically derived constants representing the stored goods; a representative temperature of the stored goods is produced. This application has near infinite possibilities in that each volume and content can be characterized and temperature represented based on a single air temperature, instilling a sense of reassurance and confidence in its thorough development process.
With VTB, the volume and buffer material used is no longer a concern. This method empowers consumers to standardize a virtual buffer tailored for each application. Standard constants can be generated for the general case, and specific constants can represent specialty materials. This flexibility puts the control in the hands of the user, allowing them to customize their buffering needs as per their specific requirements, instilling a sense of empowerment and control.
Written by Michael Rusnack, VP of Science and Engineering
