Electrode arrangement for the electrochemical analysis of electrolytic components of a liquid

• US 5,393,391 A
• Filed: 07/08/1991
• Issued: 02/28/1995
• Est. Priority Date: 04/11/1983
• Status: Expired due to Fees

• Current Assignee: Boehringer Mannheim GmbH (Roche Holding AG)
• Original Assignee: Boehringer Mannheim GmbH (Roche Holding AG)
• Inventors: Haar, Hans-Peter, Reiser, Wolfgang, Knoll, Dieter, Dietze, Werner, Herrmann, Horst
• Primary Examiner(s): NGUYEN, NAM X
• Application Number:
  US07/728,768
• Time in Patent Office: 1,331 Days
• Field of Search: 128/635, 204/403, 204/409, 204/412, 204/414, 204/415, 204/419, 204/420, 204/435, 204/416, 204/153.1, 204/153.12, 204/153.15, 204/153.16, 204/153.17
• US Class Current: 205/781.5
• CPC Class Codes: G01N 27/4035 Combination of a single ion-sensing electrode and a single reference electrode G01N27/406 and G01N27/413 take precedence
• CPC Class Codes: G01N 27/4165 for pH meters

Abstract

The present invention provides an electrode arrangement for the electrochemical analysis of components of a liquid, having a base body (7; 53; 85; 103; 139; 155; 175; 193), made of an insulating material with at least one measurement electrode (21; 57; 89; 111; 143; 157; 195) held on the base body, adapted to be brought into phase boundary contact with the liquid to be analysed, said measurement electrode being selective for a predetermined kind of ion in the liquid, and with at least one reference electrode (19; 55; 87; 109; 141; 153; 173; 197; 199) held on the base body and adapted to be brought into phase boundary contact, together with the measurement electrode, with the liquid, wherein the base body carries a removable closure part (45; 61; 91; 107; 137; 163; 187; 203) which, together with the base body, forms a closed hollow chamber (11; 52; 86; 104; 135; 159; 177; 201), the closed hollow chamber containing a standard electrolyte, especially one containing the predetermined kind of ion, defining, with the ion-selective measurement electrode, a predetermined half cell potential, said standard electrolyte being in phase boundary contact not only with the or each measurement electrode but also with the or each reference electrode.

Claims

1. A method for the electrochemical analysis of a species of ions in a sample liquid comprising providing an electrode arrangement having

a base body made of an insulating material and

a removable closure part which, together with the base body, forms a closed hollow chamber,

a measurement electrode and a reference electrode held on the base body,

said measurement electrode and said reference electrode having wettable surfaces towards said closed hollow chamber,

said reference electrode comprising an electron-conducting lead-off contact element and a reference electrolyte containing a species of ions which makes a reversible electrochemical reaction with the lead-off contact element to provide a reference potential independent of the liquid to be analyzed,

said closed hollow chamber containing a liquid preconditioning electrolyte prepacked by the manufacturer in phase boundary contact with said measurement electrode and said reference electrode and containing the species of ions to be analyzed and the species of ions which makes a reversible electrochemical reaction with the lead-off contact element of the reference electrode,

said phase boundary contact of said reference electrode and said preconditioning electrolyte being such that nonspecific exchange of ions between said reference electrolyte of the reference electrode and said preconditioning electrolyte in said closed hollow chamber is possible,

maintaining said boundary contact of said preconditioning electrolyte with said measurement electrode and said reference electrode from prepacking by the manufacturer to removal of said preconditioning electrolyte before an analytical measurement,

removing said preconditioning electrolyte from said hollow chamber before an analytical measurement,

bringing said sample liquid into phase boundary contact with said measurement electrode and said reference electrode, and

measuring the voltage between said measurement electrode and said reference electrode.

2. Method according to claim 1, wherein the hollow chamber contains a pad impregnated with the preconditioning electrolyte and said step of removing said preconditioning electrolyte comprises removing said pad.

3. A method according to claim 2, wherein the pad consists of an elastic, absorbent material in which the hollow chamber prepacked by the manufacturer is prepacked by the step of enclosing the pad, prestressed against its elasticity, in the hollow chamber.

4. A method according to claim 2, wherein the pad consists of a viscose sponge material.

5. A method according to claim 4, wherein the viscose-sponge material is a cotton-viscose sponge cloth.

6. A method according to claim 2, which includes the steps of fixing the pad to the closure part and removing the pad therewith.

7. A method according to claim 1, in which at least one of the measurement electrodes includes a lead-off electrolyte, a lead-off contact element and a barrier element arranged on a phase boundary contact surface to the hollow chamber closing off an electrode chamber for the lead-off electrolyte, said barrier element being selectively permeable for certain species of ion, wherein the lead-off electrolyte contains the species of ion to which the barrier element is permeable and in the same activity as the preconditioning electrolyte and providing an electrode arrangement includes the step of closing off the reference electrode in the direction of the hollow chamber by an electrolyte bridge permeable to all species of ions.

8. A method according to claim 1, in which at least one of the measurement electrodes includes a lead-off electrolyte, a lead-off contact element and a barrier element arranged on a phase boundary contact surface to the hollow chamber closing off an electrode chamber for the lead-off electrolyte, said barrier element being selectively permeable for certain species of ion, wherein the lead-off electrolyte contains the species of ion to which the barrier element is permeable and in the same activity as the preconditioning electrolyte and wherein the reference electrode includes a pad held on the base part, said held pad being in phase boundary contact with the lead-off contact and in which providing an electrode arrangement includes the step of impregnating said held pad with the preconditioning electrolyte of the hollow chamber as reference electrolyte.

9. A method in accordance with claim 8, in which providing an electrode arrangement includes laying the removable pad against the pad held on the base part.

10. A method according to claim 11, wherein the hollow chamber is formed by a trough on the base part and providing an electrode arrangement includes providing on the bottom of said trough phase boundary surfaces of the measurement electrode and the reference electrode.

11. A method according to claim 1, in which providing an electrode arrangement includes forming the closure part by a flexible foil jointly covering at least the phase boundary surfaces of the electrodes.

12. A method according to claim 11, in which at least one of the measurement electrodes includes a lead-off electrolyte, a lead-off contact element and a barrier element arranged on a phase boundary contact surface to the hollow chamber closing off an electrode chamber for the lead-off electrolyte, said barrier element being selectively permeable for certain species of ion, wherein the lead-off electrolyte contains the species of ion to which the barrier element is permeable and in the same activity as the preconditioning electrolyte.

13. A method according to claim 1, in which the lead-off contact element of the reference electrode contains elementary copper and the reference electrolyte contains a copper salt and, without an intermediate salt bridge, is adapted to be brought into phase boundary contact with the sample.

14. A method according to claim 13, wherein the concentration of the copper salt in the reference electrolyte is higher than 0.2 mol/litre.

15. A method according to claim 14, wherein the concentration of the copper salt in the reference electrolyte is about 1 mol/litre.

16. A method according to claim 13, wherein the lead-off contact element includes a graphite-copper mixture bound with a binding agent.

17. A method according to claim 16, wherein the lead-off contact element of the measurement electrode consists of the same material as the reference electrode and in which providing an electrode arrangement includes applying the measuring electrode and the reference electrode in the same working step.

18. A method according to claim 13, wherein the lead-off contact element includes a graphite strip which is coated with copper in the region in contact with the reference electrolyte.

19. A method according to claim 1, wherein the reference electrolyte is liquid, the reference electrode is adapted to be brought into phase boundary contact with the liquid to be analyzed by means of an electrolyte bridge preventing the mixing together of sample and reference electrolyte and the electrode chamber connecting the lead-off contact element wherein the electrolyte bridge, filled with the reference electrolyte, is so constructed by sufficiently large dimensioning of the distance and/or sufficiently small dimensioning of the cross-section between the electrolyte bridge and the lead-off contact element that the electrode reaction on the lead-off contact element within the desired measurement time is not impaired by the sample brought into contact with the electrolyte bridge.

20. A method according to claim 19, wherein the electrolyte bridge comprises a cellulose acetate membrane with a pore size of about 1 μ

m.