Figure 2. Standard curves were constructed over a concentration range of 50 µM–4000 µM isoflurane (control, closed blue diamonds, n = 4) to test the viability of sample storage at −80°C for 8 weeks (open red circles, n = 2) or shipped overnight on dry ice (open green squares, n = 5).

These procedures, storage or shipping, had no significant effect on the accuracy of the standard curves particularly in the range of 0–1000 µM, which was used for in vitro experiments (p = 0.084 for group comparison and p = 0.808 for the interaction between the groups and standard concentrations by two-way ANOVA).