Method for determining parameters of a gas-selective electrode

• US 20060027464A1
• Filed: 08/02/2005
• Published: 02/09/2006
• Est. Priority Date: 08/03/2004
• Status: Active Grant

• Current Assignee: Hach Lange GmbH (Danaher Corporation)
• Original Assignee: Hach Lange GmbH (Danaher Corporation)
• Inventors: Kussmann, Michael, Hahn, Markus, Golitz, Andreas, Bittner, Klaus, Stellmach-Hanulok, Aurelia, Battefeld, Manfred
• Granted Patent: US 7,799,202 B2
• Time in Patent Office: Days
• US Class Current: 205/775
• CPC Class Codes: G01N 27/4163 checking the operation of, or calibrating, the measuring apparatus G01N27/3274, G01N27/4175 and G01N33/0006 take precedence

Abstract

Gas-selective electrodes in liquid analyzing devices have a characteristic K with a linear portion L and a non-linear portion NL. In the non-linear portion NL, the characteristic can only be estimated so that these determinations of the concentration are rather inexact. According to the present method, the electrode is rinsed with an acid and the zero point voltage at the electrode is determined during the rinsing. Using the zero point voltage U_N thus quickly obtained, the non-linear portion NL of the characteristic K can be determined with high precision so that even low concentrations c can be determined with great accuracy.

Claims

1. Method for determining parameters of a characteristic of a gas-selective electrode (12) in an automatic liquid analyzing device (10), the method comprising the following steps:

rinsing the electrode (12) with an acid, and

determining the zero point voltage U_N present at the electrode (12) during the rinsing.

2. Method of claim 1, characterized in that the rinsing is performed during an automatic cleaning of the electrode (12).

3. Method of claim 1 or 2, characterized by the output of a depletion signal when the zero point voltage U_N reaches a predetermined depletion value.

4. Method of one of claims 1 to 3, characterized in that the electrode (12) is an ammonia electrode.

5. Method for determining parameters of a characteristic of a gas-selective electrode of one of claims 1 to 4, characterized in that the rinsing acid is citric acid.

6. Method of one of claims 1 to 5, characterized by the determination of the non-linear portion NL of the characteristic K of the electrode (12) by interpolation of the characteristic K between its linear portion L and the zero point voltage U_N according to an exponential function.

7. Method of claim 6, characterized by an interpolation according to the function

U=U_N(1−

e<sup>(E/UN(log c−

F))</sup>)

where

U is the electrode voltage,

U_N is the zero point voltage of the electrode,

E is a constant quantifying the curvature of the exponential function,

c is the concentration of the measuring gas,

c_G is the limit concentration, and

F is the position of the exponential function on the concentration axis,

and where

the linear and the non-linear portions L, NL of the characteristic K transition at a limit point G, and

the transition at the limit point G is always differentiable, and

the limit point concentration c_G or the constant of curvature E is fixed.

8. Method of claim 7, characterized in that the constant of curvature E is fixed.