The invention relates to a device for the sampling of liquids which permeate dialysis membranes, comprising cells bounded by two such membranes. The device according to the invention is suited for determining hydrochemical profiles of groundwater, in lakes and the like. The device according to the invention is a modular one, comprising a plurality of consecutive dialysis cells, spaced at predetermined intervals, in a support system. The sampler is introduced into the liquid and left there for an adequate period of time to establish an equilibrium. After removal, each of the cells is analysed and provides information on the composition of the liquid at the given depth.