Methods and apparatus for moving and concentrating particles by applying an alternating driving field and an alternating field that alters mobility of the particles. The driving field and mobility-varying field are correlated with one another. The methods and apparatus may be used to concentrate DNA or RNA in a medium, for example. Methods and apparatus for extracting particles from one medium into another involve applying an alternating driving field that causes net drift of the particles from the first medium into the second medium but no net drift of the particles in the second medium.

An object of the present invention is to provide a device for measuring electrolyte concentration capable of easily measuring a temperature difference between a sensitive membrane and liquid in the vicinity of the sensitive membrane that affects an electrolyte concentration analysis value. The device for measuring electrolyte concentration according to the present invention measures potential of an ion selective electrode at at least two or more different times while liquid is present in a flow path for introducing the liquid into the ion selective electrode, and calculates a temperature difference between the liquid and the ion selective electrode using the measured potential of the ion selective electrode at two or more different times (see FIG. 4).