Stability of mercury concentrations in frozen avian blood samples

It is unclear whether mercury concentration in wildlife tissues changes appreciably after lengthy frozen storage. To test whether such freezer-archived samples are stable, small (~10-50 μL) avian blood samples stored in capped glass capillary tubes were analyzed for total mercury concentration, and then reanalyzed after being frozen for up to 3 years. Mercury concentrations increased 6% on average over the 3 year period, but time spent frozen explained only 11% of the variation between measurements. This small amount of change suggests that archived blood samples remain useful for at least several years.