Self-activating hydratable solid-state electrode apparatus

Claim 1

An electrode assembly comprising: a planar base member; an elongated flow channel formed partially through the depth of the base member and opening to one surface thereof; a plate member fixed to the surface of the base member which has the flow channel formed therein to close off the open side of the flow channel; a first well of increased depth relative to the depth of the flow channel, formed in the base member along a portion of the length of the flow channel; a second well of increased depth relative to the depth of the first well formed in the base member along a portion of the length of the first well; an outer, planar, gas and water permeable, hydrophobic membrane layer formed over the entire surface of the first well and contacting the edges of the flow channel adjacent the first well so as to effectively form a portion of the wall of the flow channel over the first well; an intermediate, planar, gas and water permeable, hydrophilic electrolyte membrane layer containing a pH buffer underlying the outer planar membrane, within the first well; an inner, planar gas and water permeable hygroscopic electrolyte membrane layer conaining a pH buffer underlying the intermediate layer within the first well; a conductive reference electrode passing through the thickness of the base member from the side opposite that containing the first well, at a point spaced from the second well, having one end in conductive contact with the underside of said inner planar electrolyte layer; a conductive active electrode extending through the thickness of the base from the side opposite to that containing the wells at the area of the second well, so that one of its ends extends to the second well; an active, inner, water permeable, electrolyte layer formed within the second well with one of its surfaces in contact with the active electrode surface which extends to the second well; an active, outer, water permeable, polymeric pH sensitive layer filling the remaining volume of the second well so as to contact said active inner electrolyte layer and said inner planar hygroscopic electrolyte layer contained within the first well; means for introducing aqueous fluid samples into the flow channel for measuring the content of carbon dioxide gas dissolved in the fluid; and signal receiving means adopted to be connected to the ends of the active and reference electrodes opposite to the ends of those electrodes contacting the electrolyte layers; whereby the assembly, when hydrated by an aqueous fluid sample, is capable of electrochemical interaction with the carbon dioxide content of an aqueous fluid sample such that an electric potential difference is generated between said electrodes as a function of the carbon dioxide content, for measurement by said signal receiving means.