Apparatus for measuring a decomposable compound in solution

• US 6,521,184 B1
• Filed: 06/07/2000
• Issued: 02/18/2003
• Est. Priority Date: 07/29/1994
• Status: Expired due to Fees

• Current Assignee: Gambro Lundia AB (Baxter International Inc.)
• Original Assignee: Gambro AB (Baxter International Inc.)
• Inventors: Goodman-Jones, Arfon, Edgson, Raymond, Olde, Bo, Olsson, Lars-Fride
• Primary Examiner(s): SNAY, JEFFREY R
• Application Number:
  US09/589,011
• Time in Patent Office: 986 Days
• Field of Search: 436/108, 436/150, 436/174, 435/12, 422/82.02
• US Class Current: 422/82.02
• CPC Class Codes: C12Q 1/58 involving urea or urease
• CPC Class Codes: G01N 27/021 before and after chemical transformation of the material
• CPC Class Codes: G01N 33/493 urine
• CPC Class Codes: Y10T 436/171538 Urea or blood urea nitrogen
• CPC Class Codes: Y10T 436/25 including sample preparation

Abstract

Methods and apparatus for measuring the concentration of decomposable substances, such as urea, are disclosed. The disclosed methods include adding a gaseous buffer, such as CO₂, to the solution containing the decomposable compound, measuring the conductivity of the solution, decomposing the decomposable compound, measuring the conductivity of the thus-decomposed compound solution, and calculating the differential conductivities between the two measured solutions. The apparatus for carrying out these methods are also disclosed.

Claims

1. Apparatus for measuring the concentration of a decomposable compound in a solution comprising charging means for charging a buffer in gaseous form to said solution, a reactor for decomposing said decomposable compound whereby a reacted solution is formed, and measuring means for measuring the conductivities of said solution and said reacted solution whereby a differential conductivity can be calculated therefrom.

2. The apparatus of claim 1 wherein said buffer in gaseous form comprises carbon dioxide.

3. The apparatus of claim 2 wherein said decomposable compound comprises urea.

4. The apparatus of claim 3 wherein said solution comprises bicarbonate ions.

5. The apparatus of claim 2 wherein said decomposing of said decomposable compound comprises catalytically reacting said solution.

6. The apparatus of claim 5 wherein said catalytic reacting comprises reacting said solution with urease.

7. The apparatus of claim 2 including a silicon tube in contact with said solution whereby said carbon dioxide can be added to said solution by diffusion through said silicon tube.

8. The apparatus of claim 1 including a bubble detector for detecting bubbles in said reacted solution.

9. The apparatus of claim 2 including pressure increasing means for increasing the pressure of said solution in order to increase the solubility of said carbon dioxide in said solution.

10. The apparatus of claim 9 wherein said pressure increasing means is adapted to create a pressure of about 0.1 MPa.

11. The apparatus of claim 2 including temperature decreasing means for decreasing the temperature of said solution in order to increase the solubility of said carbon dioxide in said solution during said measuring step.

12. The apparatus of claim 11 wherein said temperature decreasing means is adapted to decrease said temperature to about 25°

C.

13. The apparatus of claim 1 wherein said measuring means for measuring the conductivity of said solution and said reacted solution comprises a single measurement cell.

14. The apparatus of claim 1 comprising a first conduit path and a second conduit path, said first conduit path including said reactor, and wherein said measuring means for measuring the conductivities of said solution and said reacted solution comprises a first measuring means for measuring the conductivity of said solution and a second measuring means for measuring the conductivity of said reacted solution, said first measuring means being located in said second conduit path and said second measuring means being located in said first conduit path.

15. The apparatus of claim 14 wherein said second conduit path is configured so that the flow of said solution through said first and second conduit paths to said first and second measurement cells takes approximately the same amount of time.

16. The apparatus of claim 14 wherein said heat exchanger is disposed for maintaining the temperature of said solutions in said first and second conduit paths approximately equal.

17. The apparatus of claim 4 wherein said reacted solution has a pH of between about 6 and 8.

18. The apparatus of claim 17 wherein said reacted solution has a pH of between about 6 and 7.4.

19. The apparatus of claim 4 wherein said catalyzed reaction in said reactor comprises the following reaction: