Abstract: An apparatus (1) for the measurement of a concentration of a charged species in a sample (10) is disclosed. The sample (10) comprises a plurality of types of charged species and at least one insoluble component. The apparatus (1) comprises a first circuit with a voltage control device (54) connectable to two first electrodes (30, 30?) arranged along a channel (12) holding the sample (10) and a second circuit with a conductivity detection device (55) connectable to two second electrodes (5, 5?) arranged in the channel (12). The first circuit and the second circuit are dc and ac electrically isolated from each other.

Abstract: The invention provides a method for the measurement of a concentration of a charged species in a sample, the sample having a plurality of types of charged species and at least one insoluble component. The method comprises: providing the sample on a surface of a partly permeable layer; allowing components of the sample to pass through the partly permeable layer into a channel; and separating the components into sections, such that each at least one of the sections substantially comprises a single type of the plurality of the types of charged species, and determining the charge concentration in the at least one of the sections.

Abstract: Measurement device (10) for taking a liquid sample, comprising: a measurement portion (15) with a measurement surface (20), for being in use contacted with the liquid surface and a plug portion (40) having a plurality of electrical contacts (50), wherein the plug portion (40) is mountable to a socket (110) of a measurement evaluation apparatus (100).