Ion-selective sensor with polymeric membrane having phospholipid dispersed therein

A process for making an ion-selective electrode having a structurally strong ion-selective membrane comprising the steps of:

• a) forming an electrically conductive member electrically insulated with a layer of polymeric electrical insulation, said polymeric electrical insulation in direct contact with said electrically conductive member, the conductive member having an uninsulated zone surrounded by the insulation;
• b) preparing a liquid solution comprising an ion-selective polymeric membrane formulation by dispersing a polymer, a plasticizer, an ionophore and a phospholipid in a solvent;
• c) coating the uninsulated zone of said electrically conductive member, so that the liquid solution coats, and is in direct contact with said uninsulated zone of the conductive member, and coats the polymeric electrical insulation generally adjacent to and surrounding the uninsulated zone of the conductive member;
• d) evaporating the solvent to form an ion selective membrane which coats, and is in direct contact with the uninsulated zone of the conductive member, and overlays and adheres to the polymeric electrical insulation surrounding and generally adjacent to the uninsulated zone, thereby forming an ion-selective electrode with a structurally strong membrane.

An ion-selective electrode with increased sensitivity to ions in aqueous solution fabricated in steps comprising:

• a) forming an electrically conductive member electrically insulated with a layer of polymeric electrical insulation, said polymeric electrical insulation in direct contact with said electrically conductive member, the conductive member having an uninsulated zone surrounded by the insulation;
• b) preparing a liquid solution of an ion-selective membrane formulation by dispersing a polymer, a plasticizer, an ionophore and a phospholipid in a solvent;
• c) coating the insulation free zone and the insulation generally adjacent to said zone with the liquid solution so that the liquid solution forms a coating which envelops said zone and overlays the generally adjacent surrounding insulation;
• d) evaporating the solvent to form an ion-selective membrane which coats, and is in direct contact with the uninsulated zone of the conductive member, and overlays and adheres to the polymeric electrical insulation surrounding and generally adjacent to the uninsulated zone.

A polymeric ion-selective membrane to interface with a test solution containing ions, the membrane in direct contact with a conductive substrate or in electrical contact with an internal reference electrode element, said membrane comprising:

• a polymeric matrix, the polymeric matrix having dispersed or dissolved therein;
• a plasticizer,
• an ionophore, and
• a phospholipid chosen from the group consisting of:
• CH.sub.2 OR.sup.1 CHOR.sub.2 CH.sub.2 OP(.dbd.O)(--O.sup.-)OR.sup.3
• wherein R.sup.1, and R.sup.2 are acyl groups derived from saturated or unsaturated fatty acids having from 6 to 24 carbon atoms, and R.sup.3 is --CH.sub.2 CH.sub.2 N(R.sup.4).sub.2 and the protonated form thereof, --CH.sub.2 CH.sub.2 N.sup.+ (R.sup.4).sub.3 or --CH.sub.2 CHN(R.sup.4).sub.2 CO.sub.2 H and charged forms thereof, wherein R.sup.4 is chosen from the group consisting of H, alkyl groups having from 1-14 carbon atoms or benzyl in any combination, and R.sup.3 is further inositolyl, --CH.sub.2 CHOHCH.sub.2 OR.sub.5 wherein R.sub.5 is H or CH.sub.2 OR.sup.1 CHOR.sup.2 CH.sub.2 OP(.dbd.O)(--O.sup.-)-- and protonated forms thereof, sphingomyelin;
• and mixtures thereof.

An ion-selective coated wire electrode comprising:

• a copper wire sheathed with a layer of polymeric electrical insulation comprised of polyvinylchloride, said polymeric electrical insulation comprised of polyvinylchloride in direct contact with said copper wire, said copper wire having an uninsulated tip;
• a polymeric ion-selective membrane which completely coats and is in direct contact with the uninsulated tip of the copper wire and overlays and adheres to the surrounding insulation;
• said polymeric ion-selective membrane comprising;
• a polymer matrix formed from a polymer comprising polyvinylchloride, the polymer matrix having dispersed therein,
• a plasticizer chosen from the group consisting of 2-nitrophenyl octyl ether, bis (2-ethylhexyl) sebacate dibutyl phthalate,
• an ionophore chosen from the group consisting of tridodecylamine, bis([12-crown-4]-2-methyl)2-methyl-2-dodecylmalonate, and
• further containing phosphatidylcholine dispersed therein, the phosphatidylcholine comprising about 10% to about 20% of a mixture derived from soy beans, said mixture containing other lipids.