Shipment on dry ice causes a temporary shift in pH

9 december 2014

The NBB ships frozen tissue samples on dry ice. Despite the fact that the samples are sealed in aluminum vials or plastic bags, tissue recipients should note that the presence of dry ice exposes the samples to CO2. This causes a temporary drop in pH, which results in changes to the properties of the proteins in the sample. Therefore, depending on the type of analysis to be performed on the sample, recipients may need to allow the samples to “normalize” after being removed from the shipment container. Murphy et al. (2013) describe two ways to do this: the first is allowing the samples to normalize in a freezer for 96 hours prior to performing the assay, to allow the CO2 to dissipate. If it is not possible to wait for 96 hours, a second solution is to remove the cap and vent the CO2 before thawing the sample. A summary of the article by Murphy et al. can be found here.