Noninvasive sampling of phenylalanine by reverse iontophoresis.

While iontophoresis is typically associated with drug delivery across the skin, the symmetry of the technique permits its application to the essentially noninvasive withdrawal of biologically important analytes from the subcutaneous space to the body's surface. The identification of other substances which can be monitored by this procedure, and to its optimization and development as a more general clinical chemistry tool, is a long-term objective. In this paper, we describe a preliminary in vitro investigation into the feasibility of extracting and analyzing the amino acid, phenylalanine, with the ultimate aim to develop a diagnostic test for phenylketonuria, a potentially fatal metabolic d…