In general, most compounds demonstrated good stability on cartridge, at room temperature (21 °C) over the 7 days (figure ) with overall averages -2 ± 22% and 13 ± 24% degradation for groups A and B, respectively. SPE cartridges stored in a freezer (-18 °C) were also investigated for comparison. Again, good stability of CECs was observed with <1 ± 16% and 8 ± 18% overall average for degradation for group A and B respectively. Full breakdown tables may be found in the supplementary information (tables and). Many CECs however were stable under both storage conditions, indicating a very good performance of iMME when stored at room temperature. A few CECs displayed better stability when stored in colder temperatures; for example, amphetamine reported minimal degradation at day 7 when stored in the freezer (8 ± 6% degradation) compared to 21 °C (64 ± 2%). 2-benzophenone exhibited similar levels of degradation at both temperatures, at day 7, reporting ~30% degradation. Conversely, ketoprofen appeared to be less stable at freezer temperatures on cartridge, reporting 44 ± 16% degradation at day 7 vs the 11 ± 9% degradation stored at room temperature.