Method of measuring chemical concentration iontophoretically using impermeable mask

摘要

A method for measuring the concentration of a chemical present in a blood stream of a mammalian subject is disclosed. The method involves contacting the subject's skin with a sensor assembly comprised of an ionically conducting material which contacts the skin, a working electrode which is in contact with the ionically conducting material which electrode has a catalytic surface and a mask having an opening therein. The mask is positioned between the skin and the working electrode. When the electrode is activated, chemical is transported through the skin and the ionically conductive material. The mask is positioned so that it blocks the flow into the catalytic surface except for flow which is substantially axially to the catalytic surface. Electrical signal generated at the working electrode is monitored over a period of time and correlated with a concentration of chemical present in the blood stream of the mammalian subject. The mask reduces or eliminates chemical signal which can radially transport toward the working electrode thereby reducing or eliminating edge effects making it possible to obtain a more accurate measurement.