METHOD AND APPARATUS FOR MEASURING PH OF MEDIUM SOLUTION

• US 20120253692A1
• Filed: 04/06/2012
• Published: 10/04/2012
• Est. Priority Date: 03/31/2011
• Status: Active Grant

• Current Assignee: Nihon Kohden Corporation, Tokyo Women's Medical University
• Original Assignee: Nihon Kohden Corporation, Tokyo Women's Medical University
• Inventors: OURA, Mitsuhiro, Kubo, Hirotsugu, Takeda, Sunao, Okano, Teruo, Shimizu, Tatsuya
• Granted Patent: US 9,291,572 B2
• Time in Patent Office: Days
• US Class Current: 702/30
• CPC Class Codes: C12M 41/26 of pH
• CPC Class Codes: G01N 2021/3148 using three or more wavelengths
• CPC Class Codes: G01N 2021/3181 using LEDs
• CPC Class Codes: G01N 21/80 Indicating pH value
• CPC Class Codes: G01N 2201/0627 Use of several LED's for spectral resolution
• CPC Class Codes: G01N 31/221 for investigating pH value

Abstract

A pH measuring method includes: illuminating a medium solution, which includes: a first material; and a second material, with a plurality of light beams, which includes: a first light beam, a wavelength of which corresponds to a first absorption peak; a second light beam, a wavelength of which corresponds to a second absorption peak or a second convergence point; a third light beam, a wavelength of which corresponds to a third absorption peak or a third convergence point; and a fourth light beam, a wavelength of the fourth light beam at which an absorbance of at least one of the first and second materials is converged irrespective of a pH; receiving transmitted or reflected light beams of the first to fourth light beams; measuring absorbances at the wavelengths of the received light beams respectively; and calculating a pH of the medium solution based on the absorbances.

Claims

1. A pH measuring method comprising:

illuminating a medium solution with a plurality of light beams,

the medium solution including;

a first material which, in a wavelength region of 300 nm to 800 nm, has a first absorption peak; and

a second material which, in the wavelength region of 300 nm to 800 nm, has a second absorption peak or a second convergence point where an absorbance is converged irrespective of a pH, and a third absorption peak or a third convergence point where an absorbance is converged irrespective of a pH,

the plurality of light beams including;

a first light beam, a wavelength of which corresponds to the first absorption peak;

a second light beam, a wavelength of which corresponds to the second absorption peak or the second convergence point;

a third light beam, a wavelength of which corresponds to the third absorption peak or the third convergence point; and

a fourth light beam, a wavelength of the fourth light beam at which an absorbance of at least one of the first material and the second material is converged irrespective of a pH;

receiving transmitted or reflected light beams of the first to fourth light beams;

measuring absorbances at the wavelengths of the received transmitted or reflected light beams of the first to fourth light beams respectively; and

calculating a pH of the medium solution based on the measured absorbances.

2. The pH measuring method according to claim 1, wherein the pH of the medium solution is calculated with correction using multiple regression analysis in which a logarithm of an absorbance ratio calculated from the measured absorbances is employed.

3. The pH measuring method according to claim 2, wherein the multiple regression analysis is performed by a regression expression indicated by following expression:

pH=B₀+B₁*Φ

<sub>λ

i/λ

j</sub>

Φ

<sub>λ

i/λ

j</sub>==log(A<sub>λ

i</sub>/A<sub>λ

j</sub>)

pH=B₀+B₁*Φ

<sub>λ

1/λ

4</sub>+B₂*Φ

<sub>λ

2/λ

4</sub>+B₁*Φ

<sub>λ

3/λ

4</sub>.

4. The pH measuring method according to claim 1, wherein the pH of the medium solution is calculated with an expression including a sum of the absorbance of the first material and the absorbance of the second material.

5. The pH measuring method according to claim 4, wherein the expression includes one of a first function in which the pH is a variable and a second function in which an absorption coefficient is a variable.

6. The pH measuring method according to claim 5, wherein, in a case where the expression includes the first function, the pH is calculated by following expression:

7. The pH measuring method according to claim 5, wherein, in a case where the expression includes the second function, the pH is calculated based on an absorption coefficient which is obtained by following expression:

8. The pH measuring method according to claim 4, wherein, in a case where:

the wavelength of the second light beam corresponds to the second convergence point;

the second light beam is a light beam of 480 nm;

the wavelength of the third light beam corresponds to the third convergence point;

the third light beam is a light beam of 370 nm; and

the fourth light beam is a light beam, a wavelength of the light beam at which the absorbances of both the first material and the second material are converged irrespective of a pH, the pH is calculated by following expression;

9. The pH measuring method according to claim 4, wherein, in the calculating process, a concentration of at least one of the first material and the second material is calculated based on the expression.

10. The pH measuring method according to claim 1, wherein the first material is fetal bovine serum or bovine calf serum, and the second material is phenol red.

11. The pH measuring method according to claim 1, wherein the first absorption peak is at or in a vicinity of 410 nm, the second absorption peak is at or in a vicinity of 430 nm, and the third absorption peak is at or in a vicinity of 560 nm.

12. A pH measuring apparatus incorporating the pH measuring method according to claim 1.

13. A pH measuring apparatus comprising:

a light emitting section configured to emit a plurality of light beams,

the plurality of light beams including;

a first light beam, a wavelength of which corresponds to a first absorption peak;

a second light beam, a wavelength of which corresponds to a second absorption peak or a second convergence point where an absorbance is converged irrespective of a pH;

a third light beam, a wavelength of which corresponds to a third absorption peak or a third convergence point where an absorbance is converged irrespective of a pH; and

a fourth light beam, a wavelength of the fourth light beam at which an absorbance of at least one of a first material and a second material is converged irrespective of a pH;

a light receiving section configured to measure absorbances of the wavelengths of the first to fourth light beams respectively; and

a calculating section configured to calculate a pH from values of the absorbances.