An apparatus and related method for evoking, capturing, and optionally measuring one or more parameters within a sweat sample on the surface of the skin. The apparatus includes the use of an iontophoresis chemical chamber adapted to evoke a sweat sample, the chemical chamber being matably attached to a skin capsule adapted to contain the evoked sample. The skin capsule, in turn, is provided with one or more sensors to permit the on site determination of a corresponding number of parameters within the sample.