JPH075111A - Device and method for accurately measuring gas concentration - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To provide an accurate measuring method and measuring apparatus for dissolved gas concentration in gas, vapor or sample, which is corrected for temperature change and light source light intensity change. A reference sensor including a fluorescent reagent 17 and a sensor element S connected to an optical transmission device such as an optical fiber, a prism or a glass tube, and a fluorescent reagent 15 similar to the fluorescent reagent 17 of the sensor element. It consists of R and. The reference sensor R is enclosed in an environment including air. The light emitted from the first sensor S and the reference sensor R is mechanically measured and recorded, and the gas concentration is measured based on the output from the photodetector using the correction data of the fluorescent reagent in the sensor. calculate. The reagent is fixed in the sensor with an adhesive such as a silicone adhesive.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a fluorescent chemical sensor for measuring the concentration of gas, vapor or dissolved gas in a sample. More specifically, the present invention is compensated for changes due to ambient temperature and changes in light source intensity.
The present invention relates to a method for manufacturing a fluorescent chemical sensor for measuring the concentration of gas, vapor or dissolved gas in a sample.

[0002]

BACKGROUND OF THE INVENTION Chemical sensors that use fluorescent indicators for concentration measurements based on luminescence fluorescence as a key parameter have suffered from drift and inaccuracies caused by changes in light source luminosity or ambient temperature.

Although the following solutions have been proposed in order to eliminate these drawbacks, only some of them have been successful.

In one proposal, the temperature is measured by a thermometer and the luminous intensity of the light source is measured by another detector. The measured fluorescence is corrected with reference to the table of pre-corrected data usage set for temperature correction. However, this does not compensate for all the factors that cause drift such as photobleaching, changes in indicator properties after sterilization, and changes in luminous intensity due to other optical elements of the device other than the luminescent light source.

Another proposal is to emit light at different wavelengths,
A second fluorescent reagent is used that is insensitive to the chemical changes measured. However, this has only partially achieved the optical correction, not the difference in the spectral response of the detector.

Yet another proposal measures the excited state duration instead of the luminous intensity. In this case, the ambient temperature has not been corrected and thus a separate thermometer is needed. It is also necessary to use a pulsed light source having a time constant in the order of the length of the excited electronic state of the fluorescent reagent. In such a method, the manufacturing method of the sensor is complicated and the cost is high.

Another proposal uses a fluorescent reagent immobilized in a rigid polymer such as Plexiglas as a reference indicator. However, in this method, the difference in the influence on the fluorescent substance of the environment is not corrected, and since the complete correction is not performed, it has never been actually used.

Japanese Patent Application, Japanese Patent Application No. 59-170748
The publication describes a method for measuring the presence or absence of oxygen in the environment, which method comprises exposing the sensor internally,
Measuring the extinction associated with the decrease in light intensity.
Reference devices having regions of different size or different concentration of luminescent material, preferably a polymer, are immobilized in a support that is relatively impermeable to oxygen. The indicator used is composed of a luminescent inorganic substance which exhibits luminescence when excited by visible light or ultraviolet light, and the luminescence is quenched by oxygen. The aforementioned luminescent substance belongs to a white metal complex.
This luminescent reagent on the reference element has a bandwidth in the range of higher than lower concentration. The measurement itself is performed by visually comparing the intensity of the signal with the intensity of the band on the reference sensor. The main drawback of this method is that it cannot be sufficiently accurate, of course, since the measurements are subjective and visual. As described in the specification, the accuracy of oximetry is about 2%, which is
In fact, it should be considered a semi-quantitative oximetry. Of course, if such a high precision is required, this method cannot be used.

An object of the present invention is to provide an accurate method for measuring the concentration of gas, vapor or dissolved gas in a sample.
Another object of the present invention is to provide an accurate method for measuring the dissolved gas concentration in a gas, vapor or sample, compensating for changes caused by changes in the respective gas concentrations. Yet another object of the present invention is to provide a measurement method that is objective because the gas, vapor and dissolved gas concentrations in the sample are accurately and mechanically measured. The present invention includes a fluorescent reagent, comprising at least 5
Provide a sensor element connected to an optical fiber composed of a terminal bundle, and a reference sensor having the same fluorescent reagent and connected to the other end of the optical fiber and insulated from the chemical environment. As a result, the concentration of gas, vapor and dissolved gas in the sample can be accurately measured, and the first sensor element S
Measuring and recording the light emitted from the sensor and the reference sensor R with a photodetector, and measuring the gas, vapor and dissolved gas concentrations,
Using the correction data of the fluorescent reagent in the sensor element,
The present invention relates to a detection device and a detection method characterized by performing mechanical measurement based on the output from the photodetector. This method compensates for all factors such as ambient temperature, changes in optical properties of reagents, changes in light intensity of light sources caused by electrical and thermal instability, and changes in optical fiber properties caused by changes in temperature and bending. Therefore, the measurement of gas concentration is very accurate. The measurement accuracy is generally about 0.1%, which is very accurate.

The detection device according to the present invention comprises a reference sensor which prevents the influence of chemical substances existing in the surroundings on the fluorescent light emission from the reagent by encapsulating the fluorescent reagent with an airtight coating. It is configured. A simple way to achieve this goal by this encapsulation is the presence of air, which compensates for factors such as temperature, light intensity and photobleaching for a long time. One of the advantages of the method according to the invention is that the fluorescent reagent is homogeneously arranged on the reference sensor, whereby the output from the reference sensor received by the photodetector is automatically converted into an electrical signal. Is to be converted to. In this way, the measurement of gas concentration is much more accurate and completely objective. In addition, since the fluorescent reagent in the sensor element is the same as that in the reference sensor, the emission color is the same, and the luminosity can be easily compared.

Fluorescent reagents useful in the present invention are selected from the group consisting of polycyclic aromatic molecules, homocyclic and heterocyclic molecules having fluorescent properties. The reagent is immobilized on the sensor by any of the known methods, preferably using an adhesive such as a silicone adhesive.

According to an embodiment of the invention, the alternating current generated by the detector is demodulated synchronously and the direct voltage ratio is used as the standardized intensity for the respective gas concentration calculation.

According to another embodiment of the invention, the light intensity of the light source is electronically or mechanically modulated such that the light intensity reaching the signal and reference indicator produces an alternating current that is easily distinguishable from the background illumination.

The present method can be used for measuring the gas concentration of gaseous or dissolved oxygen, carbon dioxide, etc. in a sample. The method is also useful for measuring pH of specimens. The luminous intensity light source used is selected from ultraviolet or infrared wavelengths.

The present invention is illustrated in more detail by the following three figures, but is not limited thereto. The figures are provided for a better understanding of the present invention.

In FIG. 1, the light source 1 emits radiation of wavelength λ1 which is filtered by an optical filter 2 into a 5-terminal fiber bundle 10 via a terminal 8 which comprises 50% of the fiber on the device side 19. The light incident on the port 8 is equally divided into the branches 11 and 12 on the detection head side. The branch 11 includes a holder 13, a fluorescent reagent 15, and an enclosure 16.
A reference sensor R having The branch 12 contains a signal sensor S having a holder 14 and a fluorescent reagent 17. The detection head measures the gas concentration in the chamber 18.

A portion of the fluorescent radiation of wavelength λ2> λ1 is
It is returned to the bundles (branches) 11 and 12. 50 from bundle 11
% Of the light is connected to the terminal 9 on the device side, transmitted through the λ2 filter 4, and detected by the reference detector 3. Bunch 1
The remaining 50% of the light from 2 is connected to the terminal 7 on the device side, transmitted through the second λ2 filter, and detected by the detector 5.

Of course, although optical fibers are most preferred, it is conceivable to use other transmission means instead of optical fibers.

FIG. 2 is a block diagram of a preferred embodiment of the electronic measurement and data processing unit. The light source is a halogen lamp controlled by a microprocessor for setting a constant frequency. The luminosity from the reference sensor R and the sensor element S is fed into two separate photodiodes, amplified and filtered by an analog processing unit and then converted into a digital ratio by integral A / D. The microprocessor calculates the gas concentration based on the correction data and the characteristics of the fluorescent reagent.

When the device side electrons are always the same in both channels, the ratio R / S is not affected by the light source luminous intensity change, the temperature inside the container and the time.

FIG. 3 is a schematic view showing a method in which the sensor head is brought into contact with the liquid whose oxygen content is to be measured, which is present in the container. It is noted that the two sensors, the signal sensor S and the reference sensor R, extend from the protective device bundle 1 which is connected to the main electronic box where the light source and the detector are operating. This bundle is the reference bundle 4
And signal bundle 6 are divided. Both bundles are housed in a light emitting device adapter 2 and a stainless steel protection tube 3.
The signal bundle ends with a ferrule 7 which is screwed to the specimen holder 9. The specimen holder is a metal washer 8
It is tilted from the rear side and is fixed by a stainless steel cap 11 which is also pressing an O-ring for preventing escape of gas and vapor during operation of the light emitting device. The opening on the side surface of the cap 12 allows the liquid to freely circulate on the fluorescent sample 13. The reference sensor with the fluorescent reagent is enclosed in compartment 5,
It is placed so close to the sample that it is in contact with the same temperature as the sample.

As mentioned above, the optical fiber is described as a transmission optic returning from the light source to the fluorescent material and back to the detectors R and S, but the use of other transmission means such as prisms or glass tubes. Can also be considered.

The sensor element and method made in accordance with the present invention can be used in many applications, a typical use of which is as follows. -Measurement of oxygen in various aqueous samples-Measurement of oxygen for biochemical oxygen demand known as BOD-Measurement of blood oxygen concentration using optical fiber probe-Measurement of oxygen concentration in air sample − Monitor low oxygen concentrations in various chemical reaction vessels

The following examples are illustrative, but not limiting, for a better understanding of the present invention.

[0026]

EXAMPLE A sensor element containing decacyclene immobilized with silicone adhesive as a fluorescent reagent and having an optical fiber was used to measure dissolved oxygen in a vessel containing water and dissolved air. There is. The temperature in the container is in the range of about 5 to 90 ° C., and the temperature change is mainly caused by various temperatures of the solution contained in the container.

The oximetry method described above is accurately measured during the one month period. It has been determined that the light source luminosity varies significantly by 100% or more due to the various components of the solution.
However, both these source light intensity changes and temperature changes have been corrected by the use of the sensor elements described above. Reliable results are obtained even after using the device for one month.

Although the present invention has been described with reference to several specific embodiments, many variations may be used within an apparatus system without departing from the invention as claimed. It will be understood that

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an apparatus for accurately measuring gas concentration.

FIG. 2 is a block diagram of a preferred embodiment of an electronic measurement and data processing unit.

FIG. 3 is a schematic view showing a method in which a sensor head comes into contact with a liquid, whose oxygen content is to be measured, inside a container.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Michael Reutberg, Nineth Avenue 111, Highland Park 8904, NJ, USA

Claims (12)

[Claims] 1. A fluorescent reagent is included and comprises at least 5.
From a sensor element that is connected to an optical fiber that includes a terminal bundle, and a reference sensor that has the same fluorescent reagent as above and that is connected to the other end of the optical fiber and that is insulated from the chemical environment. In a method for accurately measuring the concentration of gas, vapor or dissolved gas in a sample by providing a detection device configured, the light emitted from the first sensor element (S) and the reference sensor (R) Is measured and recorded by a photodetector, and the concentration of gas, vapor or dissolved gas in the sample is measured mechanically based on the output from the photodetector using the correction data of the fluorescent reagent in the sensor. And calculating. 2. A method according to claim 1, characterized in that the reference sensor is encapsulated by an airtight coating containing air. 3. A method according to claim 1 or 2, characterized in that the fluorescent reagent is arranged homogeneously on a reference sensor element. 4. The fluorescent reagent is characterized in that it is selected from the group consisting of polycyclic aromatic molecules, homocyclic molecules and heterocyclic molecules having fluorescent properties. The method according to any one of 1 to 3. 5. The AC voltage generated by the detector is synchronously demodulated, and the DC voltage ratio is used as a standardized intensity for gas concentration calculation. The method described. 6. A method according to claim 1, characterized in that said gas is selected from oxygen, carbon dioxide or a solution containing them. 7. The method according to claim 1, which is used for measuring the pH of a solution. 8. A fluorescence measuring device comprising: a light-emitting radiator; and a bundle of at least 5 terminals, one end of which is connected to the light source and the other end of which is separated into a first terminal and a second terminal. A fiber optic; a sensor element connected to the first terminal, containing the same fluorescent reagent,
A reference sensor element connected to the second terminal and insulated from the environment; two light detectors, one receiving the light emitted from the sensor element and the other receiving the light emitted from the reference sensor A device consisting of a vessel. 9. The fluorescence measuring device according to claim 8, wherein the light-emission radiation from the light source has wavelengths of ultraviolet rays and infrared rays. 10. The fluorescence measurement device of claim 8, wherein the reference sensor element is encapsulated in an air-containing environment. 11. The fluorescent reagent is characterized in that it is selected from the group consisting of polycyclic aromatic molecules, homocyclic and heterocyclic molecules having fluorescent properties. 8. The fluorescence measuring device according to 8 to 10. 12. The fluorescence measuring device according to claim 8, wherein the reagent is fixed in the sensor element with a silicone adhesive.