The present invention relates to methods and systems for testing for the presence of a material such as one or more analyte types within a sample and more particularly, for improved single enzyme-linked immunosorbent assay (sELISA) testing as well as other variants of single-enzyme linked molecular analysis (SELMA). The invention involves flow systems for digital counting of analytes with at least one opening (inlet/outlet). A support with hydrophilic and hydrophobic patches preferably harbours capture probes immobilised on the hydrophilic features. Nano-to-attoliter droplets are formed on the hydrophilic features. A gas phase (called gas phase seal) is applied to prevent/reduce evaporation from the droplets.