To investigate the stability of target CECs on SPE cartridge, river water was aliquoted and spiked with 100 ng L -1 of analyte solution, before being processed onto cartridge via the iMME sampler. Day 0 spiked was with 50 µL of IS at same time of analyte spiking. All proceeding samples were processed onto SPE cartridges and kept at respective conditions for the determined number of days. When samples were eluted, 50 ng of IS was added. Time points were processed in duplicate. Day 0, 1, 2, 3, 5, and 7 and storage at two different temperatures: room temperature and freezer temperature (21 °C and -18 °C).