Other studies have also observed variable stability of cocaine and potential transformation to benzoylecgonine in both river water and wastewaters . This study indicates that processing onto cartridge after sample collection could be beneficial for many CECs and reduce potential degradation. However, due to logistical limitations, this study did not investigate the stability of CECs in SA river water, which had different biochemical characteristics and may have had different patterns of stability. In summary, CECs showed different levels of stability during the 24h study, suggesting that transport to a laboratory without a cold-chain might be detrimental to sample integrity. Therefore, there is a need for on-site analyte stabilization procedures, such as presented in this paper, via the iMME sampler methodology.