PURPOSE: To obtain a component solution for thick assay at a high efficiency without loss of components in a sample by injecting a trace sample solution into a fine groove or a small recess provided on the surface of a heat generating body to concentrate or dry.

CONSTITUTION: A fine groove 1 is provided with an appropriate angle 3 of inclination on the surface of a heat generating body 2 made of silicon, glass, teflon or the like and a receiver 9 is provided as recess at the lower end of the groove as required. A heat medium hole 4 for heating and a refrigerant hole 5 are provided in the heat generating body 2. Otherwise, a cooling is made possible by utilizing the Peltier effect as obtained when current flows through a semiconductor in the normal or opposite direction or other methods. A plurality of fine grooves 1 can be arranged radially with respect to the recess 9. The heat generating body 2 may be placed in a closed vessel and the pressure is reduced in the vessel. A trace sample solution is injected into the groove 1 from a syringe 6 and thus a thick component solution can be obtained quickly by concentrating or drying it without loss in components to be assayed.