Potentiometric sensor

1. A potentiometric sensor comprising:

a measuring half cell with a conductor element;

a reference half cell with a reference element; and

a measuring circuit connected with the conductor element of the measuring half cell and the reference element of the reference half cell, the measuring circuit configured to generate a measuring signal that is dependent on a potential difference between the conductor element and the reference element,

wherein the measuring half cell includes a housing in which a first housing chamber is defined, which is closed by a first ion-selective membrane, and a first inner electrolyte contained within the first housing chamber, contacting the first ion-selective membrane and being contacted by the conductor element,

wherein the conductor element includes an inner conductor connected with the measuring circuit and a gas-tight barrier that separates the inner conductor from the first inner electrolyte.

2. The potentiometric sensor according to claim 1 , wherein the gas-tight barrier is not permeable for interfering substances that are suitable for entering into chemical reactions with the inner conductor, including gases and/or interfering ions.

3. The potentiometric sensor according to claim 2 , wherein the gas-tight barrier is chemically inert towards the interfering substances.

4. The potentiometric sensor according to claim 1 , wherein the conductor element is configured as a membrane electrode including:

the gas-tight barrier embodied as a second ion-selective membrane;

a second housing chamber arranged within the first housing chamber and closed by the second ion-selective membrane; and

a second inner electrolyte contained within the second housing chamber and contacting the second ion-selective membrane, wherein the inner conductor is in contact with the second inner electrolyte.

5. The potentiometric sensor according to claim 4 , wherein the second ion-selective membrane is a pH sensitive glass membrane.

6. The potentiometric sensor according to claim 4 , wherein the first inner electrolyte and the second inner electrolyte contain a buffer system.

7. The potentiometric sensor according to claim 4 , wherein both the first inner electrolyte and the second inner electrolyte contain an identical buffer system and have the same pH value.

8. The potentiometric sensor according to claim 4 , wherein the first inner electrolyte and the second inner electrolyte are of the same composition.

9. The potentiometric sensor according to claim 1 , wherein the conductor element includes an electroconductive inner conductor and a coating embodied as the gas-tight barrier shielding the electroconductive inner conductor from the first inner electrolyte.

10. The potentiometric sensor according to claim 9 , wherein the conductor element is embodied as an enamel electrode and the coating is formed from enamel.

11. The potentiometric sensor according to claim 9 , wherein the coating embodied as the gas-tight barrier includes at least one layer of an ion conductive polymer or an ion conductive ceramic.

12. The potentiometric sensor according to claim 9 , wherein the coating embodied as the gas-tight barrier includes at least one glass layer.

13. The potentiometric sensor according to claim 1 , wherein the conductor element includes an ion-selective field effect transistor (ISFET).

14. The potentiometric sensor according to claim 1 , wherein the reference half cell includes a reference housing chamber and a reference electrolyte contained in the reference housing chamber that is in contact with a measuring fluid that surrounds the first housing chamber via a junction arranged in a wall of the reference housing chamber.

15. The potentiometric sensor according to claim 1 , wherein the reference element and the inner conductor include a silver wire that is, at least in sections, chloride-coated.

16. The potentiometric sensor according to claim 1 , wherein the first ion-selective membrane is an ion-selective liquid membrane or a polymer membrane.