Method and Device for Determining the Concentration of Nitrite

• US 20080194033A1
• Filed: 02/13/2006
• Published: 08/14/2008
• Est. Priority Date: 02/17/2005
• Status: Active Grant

• Current Assignee: Hach Lange GmbH (Danaher Corporation)
• Original Assignee: Hach Lange GmbH (Danaher Corporation)
• Inventors: Golitz, Andreas
• Granted Patent: US 7,655,473 B2
• Time in Patent Office: Days
• US Class Current: 436/43
• CPC Class Codes: G01N 21/33 using ultraviolet light G01N21/39 takes precedence
• CPC Class Codes: Y10T 436/11 Automated chemical analysis
• CPC Class Codes: Y10T 436/17 Nitrogen containing
• CPC Class Codes: Y10T 436/173076 Nitrite or nitrate

Abstract

A method for automatically determining the concentration of nitrite in a liquid sample includes:

• • determination of the extinction of the liquid sample at a wavelength λ of 150-250 nm,
  • addition of a nitrite reducing agent to the liquid sample,
  • determination of the extinction of the reduced liquid sample at a wavelength λ of 150-250 nm, and
  • determination of the nitrite concentration from the difference between the concentration values obtained from the extinctions of the non-reduced and the reduced liquid samples.

Claims

1. A method for automatically determining the concentration of nitrite in a liquid sample, the method comprising the following method steps:

determination of the extinction of the liquid sample at a wavelength λ

of 150-250 nm,

addition of a nitrite reducing agent to said liquid sample,

determination of the extinction of the reduced liquid sample at a wavelength λ

of 150-250 nm, and

determination of a nitrite concentration from a difference between concentration values obtained from the extinctions of the non-reduced and the reduced liquid samples.

2. The method according to claim 1, wherein the reducing agent is amidosulphuric acid.

3. The method according to claim 1, wherein the nitrate concentration is obtained from the extinction of the reduced sample.

4. The method according to claim 1, wherein the liquid sample is mixed prior to the extinction determination of the reduced liquid sample.

5. The method according to claim 1, wherein the extinction determination of the liquid samples is carried out at the wavelengths λ

=213 nm and λ

=223 nm.

6. A determination device for automatically determining the concentration of nitrite in a liquid sample according to claim 1, comprising

a measuring chamber for receiving the liquid sample,

a photometer for determining the extinction of said liquid sample in said measuring chamber,

a sample transporting device for supplying and discharging said liquid sample to and from said measuring chamber, and

a reducing agent adding device for feeding a reducing agent into said measuring chamber.

7. The determination device according to claim 6, wherein the measuring chamber is defined by a pivoting fork moved in a gap, and by the walls of said gap, wherein said pivoting fork is adapted to be pivoted out of said gap for the purpose of receiving a new liquid sample, and forms part of the sample transporting device.

8. The determination device according to claim 6, wherein the two opposing gap walls each comprise an optical window.

9. The determination device according to claim 6, wherein the pivoting fork comprises a mixing tongue which is movable relative to arms of said pivoting fork.

10. The determination device according to claim 8, wherein the windows are arranged in a base plane of the gap walls, and the pivoting fork cleans said windows while being pivoted past them.

11. The determination device according to claim 6, wherein a pivoting range of the pivoting fork is shielded by a liquid-permeable cage.

12. The determination device according to claim 6, wherein said determination device is configured as an immersion probe.

13. The method according to claim 1 wherein a sample chamber for holding the liquid sample is defined by a pivotable fork and adjoining wall surfaces and the method further includes:

prior to determining the extinction of the liquid sample, pivoting the fork to capture the liquid sample.

14. The method according to claim 13 wherein the adjoining wall surfaces include windows through which light of the 150-250 nm wavelength passes and the method further includes:

cleaning the windows as the fork pivots past them.

15. The method according to claim 14 wherein a mixing tongue is mounted to the pivoting fork for movement therewith and the method further includes:

after adding the nitrate reducing agent to the liquid sample, mixing the sample and the nitrate reducing agent.

16. A device for automatically determining the concentration of nitrite in a liquid sample, the device comprising:

means for determining the extinction of the liquid sample at a wavelength λ

of 150-250 nm,

means for adding a nitrite reducing agent to said liquid sample,

means for determining the extinction of the reduced liquid sample at a wavelength λ

of 150-250 nm, and

means for determining a nitrite concentration from a difference between concentration values obtained from the determined extinctions of the non-reduced and the reduced liquid samples.