Results here have demonstrated that whilst storing SPE cartridge at freezer temperatures provides the best stability, storing cartridges at room temperature still provided stability of at least ~20% for the majority of CECs studied; especially in comparison to stability of CECs in aqueous phase, under the same conditions. For example, ofloxacin underwent no degradation when stored at room temperature on cartridge over the 24 hours, yet over the same time period and temperature in river water reported ~50% degradation (table ). Despite the indication for potential transformation of cocaine to benzoylecgonine in river water after 24 hours (±50%), both cocaine and benzoylecgonine stored on cartridge at room temperature reported minimal degradation in comparison between 10-20% (table ).