Abstract: Improved assay methods utilizing stable, enzymatically triggered chemiluminescent 1,2-dioxetanes with improved water solubility are provided. Assays are performed by a capsule chemistry analytical assay method wherein fluid capsules comprising discrete aqueous segments containing either a chemiluminescent dioxetane reagent or an activating agent separated by an oil-based isolating fluid are flowed through a conduit, and subsequently reacted to produce light.The improvement comprises using a dioxetane substituted with two or more water-solubilizing groups disposed on the dioxetane structure to provide the chemiluminescence. Compositions comprising such a dioxetane, a non-polymeric surfactant enhancer and optionally a fluorescer, provide enhanced chemiluminescence and eliminate the problem of reagent carryover when used in assays performed on capsule chemistry analytical systems.