Potentiometric measurement of chloride concentration in an acidic solution

• US 20060042961A1
• Filed: 08/30/2004
• Published: 03/02/2006
• Est. Priority Date: 08/30/2004
• Status: Abandoned Application

• Current Assignee: Beckman Coulter Incorporated (Danaher Corporation)
• Original Assignee: Beckman Coulter Incorporated (Danaher Corporation)
• Inventors: Mu, Xihai
• Application Number:
  US10/931,096
• Publication Number:
  US 20060042961A1
• Time in Patent Office: Days
• US Class Current: 205/775
• CPC Class Codes: G01N 33/49 Blood chemical methods for determining blood cell populations G01N33/5094; chemical analysis of blood groups or blood types G01N33/80

Abstract

Measuring chloride ions in a sample solution at acidic pH with a potentiometric silver chloride electrode is disclosed.

Claims

1. A method of measuring the concentration of chloride ions in a sample solution initially having a pH greater than 5, comprising the steps of:

(a) adding an acidic reagent to the sample solution to lower the pH of the sample solution to 5 or less, thereby forming an acidified sample solution;

(b) contacting the acidified sample solution with an ion sensitive electrode comprising silver chloride; and

(c) measuring the electric potential of the acidified sample solution with the electrode.

2. The method of claim 1, wherein the electrode is a solid state silver chloride electrode.

3. The method of claim 1, additionally comprising the step of converting the electric potential measured in step (c) into chloride concentration for the sample solution.

4. The method of claim 1, wherein step (a) comprises lowering the pH of the sample to less than about 4.

5. The method of claim 4, wherein step (a) comprises lowering the pH of the sample to less than about 3.

6. The method of claim 5, wherein step (a) comprises lowering the pH of the sample to about 2.5.

7. The method of claim 1, wherein steps (a) and (b) are conducted simultaneously.

8. A method of measuring the concentration of chloride ions in a clinical sample, comprising the steps of:

(a) obtaining a solution comprising the clinical sample, wherein the solution has a pH of between about 6 and 8;

(b) adding an acidic reagent to the solution to lower the pH of the solution to 5 or less, thereby forming an acidified solution;

(c) contacting the acidified solution with an ion sensitive electrode comprising silver chloride; and

(d) measuring the electric potential of the acidified solution with the electrode.

9. The method of claim 8, additionally comprising the step of converting the electric potential measured in step (d) into chloride concentration for the sample solution.

10. The method of claim 8, wherein step (b) comprises lowering the pH of the solution to less than about 4.

11. The method of claim 10, wherein step (b) comprises lowering the pH of the solution to about 2.5.

12. A method of measuring the concentration of chloride ions in a plurality of sample solutions, comprising:

(a) contacting one of the plurality of sample solutions with an ion selective electrode comprising silver chloride;

(b) measuring the electric potential of the sample solution of step (a) with the electrode;

(c) removing the sample solution of step (a);

(d) contacting the electrode with one or more buffer solutions;

(e) repeating steps (a) through (d) for each of the remaining sample solutions over a period of more than 2 months, thereby measuring the concentration of chloride ions in each of the plurality of sample solutions; and

(f) maintaining substantially all of the plurality of sample solutions and the one or more buffer solutions at a pH of 5 or less so that the electrode decreases in sensitivity by less than 30 percent over the period of more than 2 months.

13. The method of claim 12, further comprising the steps of:

(i) testing the electrode for a drop in sensitivity; and

(ii) replacing the electrode after a drop in sensitivity of 30 percent or greater is detected.

14. The method of claim 12, comprising the steps prior to step (a) of:

providing one or more sample solutions initially having a pH greater than 5; and

then

lowering the pH of the one or more sample solutions to pH 5 or less.

15. The method of claim 12, wherein the electrode is in contact with the sample solutions and the one or more buffer solutions for a period of more than 4 months, and wherein the electrode decreases in sensitivity by less than 30 percent during the period of more than 4 months.

16. The method of claim 12, wherein the electrode decreases in sensitivity by less than 20 percent during the period of more than 2 months.

17. A method of operating an ion selective electrode comprising silver chloride, comprising the steps of:

(a) calibrating the electrode;

(b) after step (a), measuring chloride concentration in one or more sample solutions having a pH of 5 or less by;

(i) contacting the electrode with the one or more sample solutions;

(ii) obtaining an electric potential measurement of the one or more sample solutions with the electrode to determine chloride concentration information; and

(iii) contacting the electrode with one or more buffer solutions having a pH of 5 or less, wherein the electrode is in substantially continuous contact with the one or more sample solutions and the one or more buffer solutions for a period of more than 3 days; and

(c) after step (b), evaluating the calibration of the electrode by;

(i) contacting the electrode with a solution having a known chloride concentration;

(ii) obtaining a chloride concentration measurement with the electrode, wherein the chloride concentration measurement obtained by the electrode is different by less than about 3 percent from the known chloride concentration of the solution having a known chloride concentration.

18. The method of claim 17, wherein step (a) comprises:

(i) contacting the electrode with a solution having a known chloride concentration;

(ii) obtaining a chloride concentration measurement with the electrode; and

then

(iii) adjusting the electrode so that the chloride concentration measurement corresponds to the known chloride concentration of the solution.

19. The method of claim 17, comprising, prior to step (b), the steps of:

providing one or more sample solutions initially having a pH greater than 5; and

then

lowering the pH of the one or more sample solutions to a pH of 5 or less.

20. The method of claim 17, wherein the electrode is in substantially continuous contact with the sample solution and the one or more buffer solutions for a period of more than 5 days, and wherein the concentration of the solution of known chloride concentration measured by the electrode changes by less than about 3 percent during the period of more than 5 days.

21. A method for measuring the concentration of ions in a sample solution with an analytical instrument, comprising:

(a) contacting the sample solution with an ion selective electrode in the instrument, wherein the sample solution is at a pH greater than 5, and wherein the ion selective electrode is adapted to measure the electric potential of an ionic species in the solution other than chloride;

(b) measuring the electric potential of the sample solution with the electrode;

(c) lowering the pH of the solution to 5 or less, thereby forming an acidified sample solution;

(d) contacting the acidified sample solution with an electrode comprising silver chloride; and

(e) measuring the electric potential of the acidified solution with the electrode comprising silver chloride.

22. The method of claim 21, wherein the ionic species in the solution other than chloride is selected from the group consisting of sodium, potassium, lithium, and calcium.

23. The method of claim 21, wherein the electrode comprising silver chloride is a solid state silver chloride electrode.

24. The method of claim 21, additionally comprising the step of converting the electric potential of the acidified sample solution measured in step (d) into chloride concentration information for the sample solution.

25. The method of claim 21, wherein step (c) comprises lowering the pH of the sample to less than about 4.

26. The method of claim 26, wherein step (c) comprises lowering the pH of the sample to about 2.5.

27. A system for measuring the concentration of chloride ions in a sample solution, comprising:

(a) an ion selective electrode adapted to measure the electric potential of an ionic species in the sample solution other than chloride at a pH greater than 5, the ion selective electrode being in communication with a first container for holding the sample solution;

(b) an ion selective electrode comprising silver chloride in communication with a second container for holding the sample solution;

(c) a first duct for conducting the sample solution from the first container to the second container;

(d) a container for holding an acidic reagent adapted to lower the pH of a solution initially at a pH greater than 5 to a pH of 5 or less; and

(e) a second duct for conducting the acidic reagent to the first duct or the second container.