Sensor element for determining the amount of oxygen dissolved in a sample

• US 5,272,090 A
• Filed: 03/31/1992
• Issued: 12/21/1993
• Est. Priority Date: 03/31/1992
• Status: Expired due to Fees

• Current Assignee: Misha Roitberg, Moshe Gavish
• Original Assignee: Misha Roitberg, Moshe Gavish
• Inventors: Gavish, Moshe, Roitberg, Misha
• Primary Examiner(s): Johnston, Jill A.
• Application Number:
  US07/861,189
• Time in Patent Office: 630 Days
• Field of Search: 422/82.05-82.08, 436/68, 436/133, 436/136, 436/172, 128/634, 385/12, 385/13, 356/402, 356/409, 356/411
• US Class Current: 436/133
• CPC Class Codes: G01N 2021/6432 Quenching
• CPC Class Codes: G01N 2021/6434 Optrodes
• CPC Class Codes: G01N 2021/7786 Fluorescence
• CPC Class Codes: G01N 21/643 non-biological material
• CPC Class Codes: G01N 21/7703 using reagent-clad optical fibres or optical waveguides using measurement of total internal reflection or attenuated total reflection G01N21/552; optical fibres or waveguides per se G02B
• CPC Class Codes: Y10T 436/204998 Inorganic carbon compounds
• CPC Class Codes: Y10T 436/207497 Molecular oxygen

Abstract

A method and apparatus are described for an accurate determination of the concentration of a gas, vapor or a gas dissolved in a sample which compensate for variations in temperature and light - source intensity. The apparatus comprises a sensor containing a fluorescent reagent connected to a transfer optic, such as fiber optics prism or glas pipes, and to a reference sensor containing the same fluorescent reagent. The reference sensor is encapsulated in an environment containing air. The light emitted from the first sensor and the reference sensor is determined and recorded automatically, the concentration of the gas being calculated based on the output from said light detectors using calibration data of the fluorescent reagent present in the sensors. The reagent is immobilized in the sensor by a glue, such as a silicon glue.

Claims

1. A method for an accurate determination of the concentration of a gas, vapour or a gas dissolved in a liquid sample comprising

providing a sensing apparatus which comprises

an optical fiber containing at least five terminal bundles, of which one end is divided into first, second and third terminals and a first terminal is connected to a light source and the other end is divided into fourth and fifth terminals,

a sensor element containing a fluorescent reagent, and connected to the fourth terminal, the sensor element being exposed to a chemical environment,

a reference sensor element containing the same fluorescent reagent and connected to the fifth terminal, the reference sensor element being insulated from the chemical environment, and

first and second light detectors, the first light detector receiving light emitted from the sensor element that passes through the second and fourth terminals and the second light detector receiving light emitted from the reference sensor element that passes through the third and fifth terminals;

transmitting light through the optical fiber and measuring the concentration of the gas, vapour or gas dissolved in a liquid sample in the sensor and reference sensor elements;

transmitting light emitted by the sensor and reference sensor elements through the optical fiber and detecting the light so transmitted with the first and second light detectors and recording the output of the first and second light detectors; and

automatically calculating the concentration of the gas, vapour or gas dissolved in the liquid sample based on the output from said first and second light detectors using calibration data developed from exposure of the fluorescent reagent present in the sensor and reference sensor elements to the gas, vapour or gas dissolved in a liquid sample.

2. The method according to claim 1, wherein said reference sensor element is encapsulated within a fermentation adaptor and a stainless steel protecting tube and tight covered by an O-ring, the tight cover containing air.

3. The method according to claim 1, wherein the fluorescent reagent is located homogeneously in the reference sensor element.

4. The method according to claim 1, wherein the fluorescent reagent is selected from the group consisting of polycyclic aromatic molecules which posses the luminescent property.

5. The method according to claim 1, wherein an AC voltage is generated by the first and second light detectors and the AC voltage is synchronously demodulated into DC voltages and the ratio of the DC voltages is used as a normalized intensity for the calculation of the concentration of the gas, vapour or gas dissolved in a liquid sample.

6. The method according to claim 1, wherein said gas, vapour or gas dissolved in a liquid sample is selected from oxygen, carbon dioxide or a solution containing oxygen and carbon dioxide.

7. A fluorescent measuring apparatus comprising:

a light source emitting radiation;

an optical-fiber comprising at least five terminal bundles, of which one end is divided into first, second and third terminals and the first terminal is connected to said light source and the other end of said optical-fiber is divided into fourth and fifth terminals;

a sensor element exposed to a chemical environment and connected to the fourth terminal, and reference sensor element connected to the fifth terminal, both said sensor element and said reference sensor element containing the same fluorescent reagent, the reference sensor element being insulated from the chemical environment; and

first and second light detectors, the first light detector receiving light emitted from the sensor element that passes through the second and fourth terminals and the second light detector receiving light emitted from the reference sensor element that passes through the third and fifth terminals.

8. The fluorescent measuring apparatus according to claim 7, wherein said light source emits radiation in the wavelengths of ultraviolet and infrared.

9. The fluorescent measuring apparatus according to claim 7, wherein said reference sensor element is encapsulated in a housing which allows air to surround the reference sensor element.

10. The fluorescent measuring apparatus according to claim 7, further comprising means for automatically calculating the concentration of a gas, vapour or a gas dissolved in a liquid sample from the outputs of said first and second light detectors and further including means for compensating for any changes in the temperature and light source intensity.