Gravity filtration of environmental DNA: A simple, fast, and power-free method

Filtration is required during the collection of trace amounts of environmental DNA (eDNA) from water samples to achieve a concentration sufficient for downstream molecular experiments. To date, collected water samples have been filtered by humans or electric power using various instruments. We developed a simple gravity filtration system that does not need for an external force. The system comprises a plastic bag filled with a water sample (1 L), a filter cartridge, and a long plastic tube (e.g., 2 m). When hung at a height equal to the tube length, this filtration unit can enable power-free collection and concentration of eDNA at any remote location within a reasonable time (10–60 min). • A simple, rapid, power-free, practical filtration system for environmental DNA analysis is reported. • If there is a place to hang the filtration system, filtration can be performed anywhere. • The filtration speed increased when the system was hung higher.