Microchip-type oxygen gas sensor based on differential potentiometry

A microchip-based potentiometric multi-sensor capable of detecting two or more ions and gas species at the same time comprising

• a) an alumina substrate 5;
• b) an electrode unit I comprising Ag/AgCl electrode 12 on a Ag—pt layer 11;
• a hydrogel layer 21, placed on the Ag/AgCl electrode 12;
• and an aromatic polyurethane membrane 22, deposited over the hydrogel layer 21, wherein the aromatic polyurethane membrane 22 is an outer membrane of a insulating film 6,
• c) an electrode unit II comprising Ag/AgCl electrode 12 on a Ag—Pt layer 11;
• a buffered hydrogel layer 14, placed on the Ag/AgCl electrode 12;
• and hydrogen ion selective membrane 15, placed top the buffered hydrogel layer 14, which hydrogen ion selective membrane 15 is enclosed within a well formed by the insulating film 6,
• d) an electrode unit III comprising Ag/AgCl electrode 12 on a Ag—pt layer 11;
• a unbuffered hydrogel layer 31, placed on the Ag/AgCl electrode 12;
• and hydrogen ion selective membrane 15, deposited over the unbuffered hydrogel layer 31, which hydrogen ion selective membrane 15 is enclosed within the well formed by the insulating film 6,
• e) an electrode unit IV comprising a cobalt-plated electrode layer 13 on a Ag—Pt layer 11;
• a buffered hydrogel layer 14, placed on the Ag/AgCl electrode 12;
• and a hydrogen ion selective membrane 15, deposited over the buffered hydrogel layer 14, which hydrogen ion selective membrane 15 is enclosed within the well formed by the insulating film 6, and
• f) an electrode unit V comprises Ag/AgCl electrode 12 on a Ag—Pt layer 11;
• a potassium ion selective membrane 41 deposited over the Ag/AgCl electrode 12, which potassium ion selective membrane 41 is enclosed within the well formed by the insulating film 6,
• whereby said insulating film 6 is deposited over the entire aluminum substrate 5, except for the areas of the electrodes so as to insulate the electrode units I˜V.