JPS59500833A - Method for measuring gas concentration, gas sensor and device therefor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Gas sensors and how to use them Technical field The present invention is applicable to various gases (cO2, CO, H2S, hydrocarbons, etc.) in gases and liquids. A sensor that electrochemically measures the concentration of alcohol (including alcohol vapor, NOx, etc.) - related. Further details or electrochemically by oxidative adsorption (e.g. in the case of alcohols) or by special Platinum and The partial pressure of a gas can be determined by measuring the adsorbed species generated on the surface of other metals. a sensor for detecting a gas or liquid, and near the same time but independently if necessary. Relating to a sensor for quantifying oxygen content in the body.

Background technology Electrochemical sensors currently in use are of the potentiometric or polarographic type. (including other current measurement methods).

The potentiometer type sensor is basically a modified p)] electrode, and its working principle is based on H ion. It is based on the measurement of a potential that is effectively a linear function of the logarithm of the concentration of the ion. typically , carbon dioxide, hydrogen sulfide, nitrogen oxides, sulfur dioxide, etc. Sensors belong to this category. - As an example, this sensor uses pH and carbon dioxide. The relationship between partial pressure is ΔpH=0.97ΔAog], oPco2.

The change in potential for one unit of pH at room temperature is less than 60 mV, so It is clear that the measurement method is inherently inaccurate (Pco2 varies by a factor of 2). (This results in a change of 18 mV). Furthermore, glass electrodes! Takeo's other type of electrodes, For example palladium/palladium oxide, iridium/iridium oxide or solid Even if an electrode is used, this type of sensor does not require a pH voltage. Inherently suffers from the problems of poles: low sensitivity, slow response time, and significant deviation. .

Polarographic and other sensors based on current measurement have two or three Equipped with electrodes. In any case, the working principle of this type of sensor is that the measured based on the measurement of the current, usually the limiting current, of an oxidation (or reduction) reaction for a gas ing. The strength of this current is proportional to the partial pressure of the gas in the environment. Typically, Electrochemical sensors for oxygen, carbon oxides and alcohols belong to this type. Ru. The major problem with this type of sensor is its low sensitivity and poor selectivity.

The main objective of the present invention is to reduce the amount of chemisorbed species generated on metal electrodes under certain conditions. Various gases (e.g. co, CO2, H2S, N Provides an electrochemical method for measuring the partial pressure of OX, alcohol vapor, hydrocarbons, etc. That's true.

Another object of the present invention is to provide a single sensor for measuring partial pressures of various gases and oxygen as described above. It is an object of the present invention to provide an electrochemical method for measuring content substantially simultaneously and independently.

Yet another object of the invention is to electrochemically (via reduction or oxidation processes) and measures the amount of adsorbed species generated on the electrode surface non-electrochemically (i.e. chemisorption) A sensor that measures the partial pressure of a specific gas in a mixture of gases and liquids by The goal is to provide services.

Yet another object of the present invention is to measure the partial pressures of various gases as described above with a single sensor. By providing a sensor for near-simultaneously and independently measuring be.

These and other objects of the invention will be apparent from the detailed description below. cormorant.

The underlying concept for achieving the objectives of the present invention is that, under certain conditions, platinum or other By measuring the amount of adsorbed electroactive species generated on the electrode surface, this amount (adhesion amount ) is a function only of the partial pressure of the gas being measured under the given conditions. of the sensor Formally, it is formed by a hydrophobic diaphragm that is impermeable to electrolytes or permeable to gases. Each electrode is isolated from the surrounding environment. The electrode side behind this thin film is There exists an electrolyte with gas species and nfl solubility (in the case of CO2, for example, this The electrolyte can be an acid, a phosphate buffer, or a bicarbonate containing an inert salt. ).

The sensor includes a reference electrode in addition to a working and counter electrode that generates adsorbed electroactive species. It has an electrolytic bridge that connects to the Setake external reference station. In some cases, the counter electrode is a reference It can also be used as an electrode. The working electrode is platinum or other noble metal, e.g. palladium, iridium, rhodium, osmium, ruthenium, gold and It is made of various alloys of these materials or alloys with base metals, and has a smooth surface or a large surface area. can do.

Preferably, the measurement is based on a potential-controlled method, which means Apply at least two potentials and ξruses in a short period of time using the Yosukunoto It is given to the pole and is done as follows. ) Electrochemical (by partial oxidation or reduction) on the working electrode due to the reactions involved or non-electrochemically (by chemisorption) to generate adsorbed electroactive species. Control the sea urchin adsorbate generation potential pulse.

The amount of adsorbed species (N) depends on the electrode potential, electrode surface roughness coefficient, gas concentration near the electricity supply, and and time. The gas concentration in the region closest to the electrode is related to the partial pressure of the gas in the external environment. It varies depending on the mass transfer properties of the diaphragm and electrolyte. “Diaphragm limited” sensor If, before saturation, the amount of adsorbate produced is It depends on the permeability of the membrane, if any, and the partial pressure of the gas being measured. Alternatively, the amount of gas The pressure is calculated using the kinetic formation rate of the adsorbate or between the adsorbate loading and the gas junction. It can be determined using the isotherm equation.

(B) During the measurement potential pulse, the charge due to oxidation of the adsorbate is measured. child The charge on is a function of the partial pressure of the gas being measured.

(C) If necessary, include a pulse of activation (-! level purification) potential. By applying a high (anodic) potential during this time, impurities on the electrode surface can be removed. be purified.

These potential "-pulses" do not necessarily have to be constant potential pulses. These are prescribed can be a function of the potential over time. From one potential pulse to the next potential pulse The change in potential can be any step, and the potential changes gradually over time. It may also occur according to a number. Specifically, dl, the potential pulse for measurement is potential dynamics. i.e., to control the potential-time function between the working (sensing) electrode and the reference electrode. or by using a galvanostat, i.e., the working electrode and the reference electrode. can be obtained by controlling the current between. In either method, The charge that flows during the measurement phase can be electronically integrated into the current and converted into a partial pressure. It can be determined by

Due to the presence of a hydrophobic diaphragm, non-volatile inhibitors and coexistence outside the diaphragm during measurements There is no effect by the reactants. The adsorbate generation current is integrated during the adsorbate generation pulse. Therefore, the interaction with oxygen is kept extremely low, and the current due to temporary oxygen reduction is not included. stomach.

This electrochemical gas detection method is highly sensitive. The reason is that this method uses liquid Stripping portammetry technique commonly used to measure trace metals in This is because, similar to , the current required to oxidize the adsorbed species on the electrode is integrated.

This electrochemical gas detection method is simple, standard polarographic or potentiometric. method, it inherently has much higher selectivity in the presence of co-reactants.

The reason is that this gas detection method is not operated or tested. Analysis techniques for parameters and output data This is because you can choose from a wide variety of techniques.

The selectivity of the gas sensor can be significantly increased by the items described in 1 to 5 below. can be done 1. Selection of adsorption potential Since the adsorption rate depends on the potential, the adsorption potential and ξrus are important in terms of sensor selectivity. Find the necessary parameters. For example, CO is 0% for RHE (reversible hydrogen electrode). ．． CO2 is adsorbed on platinum in the potential range of 0-0.7 sv, while CO2 is ．． Adsorbed by reduction at 4v. Therefore, the adsorption potential is set to high <(0,40~0 ．． 75v range) to eliminate interference with CO2 in the gas mixture is possible.

2 Separation of current peaks When two or more chemical species are chemisorbed on the electrode, each oxidation current peak is constantly swept. The speed of the anode ramp is sufficient (to 1 ifflf) to separate the individual within a predetermined potential range. The peaks (dimensions or related current peaks) can be integrated. As an example, [− The respective oxidation current peaks of reduced CO2J and CQ are approximately 100 mV apart.

Furthermore, in the case of irreversible oxidation of adsorbed species, the peak potential is a function of the electron transfer rate. The separation of each oxidation current peak is performed by changing the slope of the anode tilt. can be done. Alternatively, the anode slope can be “cut” into several parts with different slope ratios. You can do J. Fine-tune the slope percentage and use the microprocessor for integration. Selectivity can be improved by appropriately selecting each part of the output current curve.

Different materials have different adsorption affinities for gases. Therefore, a certain potential range In the interior, certain gases are adsorbed by certain particles but not by other materials. There is a good chance that something will happen. For example, CO is o, o ~ 0.75 V (at R1-IF On the other hand, rhodium 10 is adsorbed by platinum at a potential of -0,2 to +〇, Adsorption occurs at 5 V. In the case of platinum with black platinum, the potential is wrinkled compared to that of smooth platinum. move slowly. Similarly, the oxidation current peaks of interfering substances are different on different surfaces. It may occur due to electric potential. This greatly improves selectivity.

4. Absence of adsorption current peak For coexisting reactants such as oxygen that do not adsorb on platinum, the corresponding adsorption current peak ku is not allowed. In this case, the limiting current (polarographic) method is used to A sensor can be used to determine its concentration.

5. Adjustment of sensor operating temperature For example, hydrocarbons (e.g. cH4)Vi strongly adsorbs at high temperatures, but at room temperature the amount of adhesion increases. It is known that it can be almost ignored. Do not expose the sensor to high temperatures (e.g. 60'C or higher). Figure 1 shows that by operating the same sensor more selectively for methane (above), A longitudinal cross-sectional view of the in vitro sensor, with the span electrode fd not shown: FIG. 2 is a cross-sectional view of the sensor of FIG. 1.

FIG. 3 is a schematic cross-sectional view along the axis of a sensor according to another design: FIG. 4 is a schematic axial cross-sectional view of yet another cell of another design; FIG. 5 is a schematic cross-sectional view along the axial direction of yet another hill of another design: FIG. 6 is a block diagram of a potential-controlled electrochemical measurement system; FIG. 7 shows the waveform of a potential controlled sensor cycle including a purification phase; FIG. 8 shows the waveform of a potential-controlled sensor cycle without a purification step; Figure 9 shows another waveform of the potential controlled sensor cycle; Figure 10 shows the potential controlled sensor cycle. Circycle further (C is another waveform; Figure 11 is a block diagram of an electrochemical measurement system using potential control/galvanostat control. It is a diagram; Figure 11 and Figure 11 are potential control/galvano stand control (current control) measurement system. Figure 12 shows the electrochemical measurement using the galvanostatic control method. It is a block diagram of a fixed system; Figures 12- and 12-b show the current for one hour in the measurement system controlled by the galvanostat. The curve and the potential-time curve are shown respectively; Figure 13 shows the reduction and adsorption measurement of carbon dioxide on the electrode surface where the measurement is carried out at open circuit potential. Fig. 14 (79 mV for one reversible hydrogen electrode) is shown. Current-potential for each ladder concentration of carbon dioxide obtained after reductive adsorption for 40 seconds at shows a curve; Figure 15 is a series of Qs showing the effect of tacts. X vs. P. 03 curve; Figure 16 shows the current-potential curve for each carbon monoxide concentration; Figure 17 is the Qox vs. PCO curve, and Figure 18 is the jads time. ) Current-potential curve for H2S at constant concentration and constant adsorption potential shows.

Best mode for carrying out the invention As shown in Figures 1 and 2, the sensor IO that measures carbon dioxide in a liquid is A plastic cylindrical part 22 and a rectangular platinum electrode measuring approximately 1.25 mm x 6 mm. The electrodes 12 have electrodes 12 of the same shape and size located in parallel relation to each other. It is sandwiched between two platinum counter electrodes 14 that are in contact with each other. The surface of each electrode is 240.3 20. Polished flat with 400 and 600 grain SIC paper. then Platinum black was applied to this flat surface to give a surface roughness coefficient of approximately 100.

On the smooth base surface of the resin part, there is a capillary tube 2f) which runs parallel to the axis of the cylindrical part. There are 8. This capillary is filled with hydrophilic fibers 24 to prevent convection, and see Used as an ion bridge for electrodes. Thickness pre-wetted with electrolytic g (internal electrolyte) Glass with a diameter of 125 μm [woven fabric spacers 26 are placed over the entire surface of each electrode] A Teflon membrane channel with a pore size of 0.2 μm and a thickness of 5 μm is provided on the wet spacer. is used to separate the internal electrodes from the external environment.

As an example, we demonstrate the carbon dioxide measurement performance of this electrochemical detection method in terms of dissolved carbon dioxide content. The liquid was prepared under the following conditions: 1M H2S0. as internal electrolyte The Taleb-Slinger solution is a carbon dioxide-containing liquid. [Krebs-Lin The Kerr solution is NaC7 = 0.109 M i KCl = 0.004 M ;NaHCO3=0.024M;MI? :8.04=0.0006 M: and NaH2PO4==0.001M. ] Electrochemical cell The temperature is maintained at 37°C. A dynamic hydrogen electrode (DHE) was used as a reference electrode. .

Results are reported as values for the reversible hydrogen electrode (RHE). 0~760 Premixed and preanalyzed each containing a wide range of Pco2 in mmHg A seed C02/N2 mixture was used.

The gas was first passed through a presaturator maintained at 37°C before entering the cell. child The cell was allowed to equilibrate for at least 20 minutes before taking a new gas composition measurement. .

Prior to measurement, a triangular wave similar to the one shown in Figure 8 was drawn at a sweep speed of 500 mv/sec. The working electrode was cleaned using a cycle of 0 to 1500 mV (vs. RWE). . Next, the potential of the working electrode is set to T'ads period IVl (in each of the three sets of measurements). (40.60 and 120 seconds) Eads (70mV vs. RHE) A carbon dioxide reduction plate layer was applied. Immediately after this, the sweep speed was 50 mV/sec. A vertical tilt (AR) was applied to oxidize the adsorbed "reduced C02" species. oxidation current It was recorded as a function of potential and entered at line 141. 500-800mV (vs. RH The current peak located at E) is due to the oxidation of "reduced CO2". Integrate this current Charge amount (Qox) (background charge, i.e., when CO2 is not present) ), and use this as a measure of chemisorption "reduced CO2". Pco2 was determined quantitatively. Alternatively, this current peak is of QOX and therefore It can also be used as e7T'< of Pco. princeton applied Research (Pr1nceton Applied, Re5earch) 17 3 potentiostat, Hewlett Paracard (Hewlett Pack) ard) 331OB H number generator and Hewlett backer door 047 An AX-Y recorder was used for measurements. Figure 15 shows three sets of measurements of the charge Current QoX is plotted as a function of Pco2. As shown in Figure 15, 0 Within a range of 150 mmHg, the charging current changes approximately linearly with PCO2.

Measurement of Kishise 42-co. As a second example, the carbon monoxide measurement performance of this sensor can be compared to dissolved carbon monoxide content. The body ((was investigated under the following conditions.

IMH2So, i used as internal electrolyte, external fluid containing carbon monoxide . Electrochemical li]lI determination is performed at room temperature. Wide range from O to 760mmHg A premixed CO/N2 mix wJ containing 30% of PCO was used. carbon dioxide Similar operational precautions and laboratory techniques were used as described in the previous example of detection.

Prior to the measurement, the sweep rate was 500 mV/sec, similar to that shown in Figure 8. Cycle the working electrode from O to 1500 mV (vs. RHE) using a triangular wave. Purified. Next, the potential of the working electrode is set to tad, for a period of s (5 seconds in actual measurement). Chemical adsorption of CO was performed using Eaas (70 mV vs. RHE).

Immediately after this, an anode potential gradient (AR) is applied at a sweep rate of 50 mV/sec to Chemisorbed CO was oxidized. The oxidation current was recorded as a function of potential and is shown in Figure 16. did. The current peak within the potential range of 700-900 mV is 002 of chemisorbed CO. This is due to oxidation to. This current is integrated to obtain the amount of charge (Qox) (co is subtract the background charge if it is not present) and use it as a measure of PCO. there was. In FIG. 17, the integrated charging current QOX is Pc.

It is written as a function of . Valorized hydrogen is detected within the range of 38 to 380 mmHg. was measured for a dissolved hydrogen-containing liquid under the following conditions: 1M H2SO, was used as the internal electrolyte and carried out at room temperature. Premixed and preanalyzed H2 A H2S/N2 mixture with an S concentration of 850 ppm was used. carbon dioxide and monoxide Using the same operational precautions and experimental techniques as applied in each of the previous carbon examples, .

Prior to each measurement, the platinum working electrode was was purified by cycling from 0 to 1500 mV (vs. RHE). Then the potential of the working electrode H2S was adsorbed by setting Eads to a period of time tads. Typically, E The range of ads is 70-370 mV (vs. RHE), and the tads is 1-20 minutes. It was between.

Then, immediately apply a 1'4i sand potential gradient (AR) at 5Q mV/sec to conduct electricity. The H2S adsorbed on the pole was oxidized. The peak of the oxidation current is shown in Figure 18 at 7F. It was 1200 mV (vs. RHE) as shown in the figure.

As expected, the current peak serves as an indication of the amount of H2S adsorbed to the working electrode. With the increase in ads, I have become more dog-like.

At the same time, the hydrogen adsorption charging current within the potential range of 0~3oomv is the chemisorption H2S building. It decreases as it increases. This provides another method for measuring chemisorbed gases. Ru.

In the gas measurement test mentioned above, the sensor can be changed as shown in Figure 3. Wear. In FIG. 3, the sensor includes a housing 36, a working electrode 12 and a counter electrode 1. 4. The internal electrolyte is contained in a g reservoir 38. Counter electrode 14 and reference electrode 40 is located within the electrolyte reservoir and away from the working electrode. This type of sensor can measure the concentration of gases in liquids as well as gases.

As shown in FIG. 4, the reference electrode is placed within a cylindrical housing according to the embodiment of FIG. , may be provided in an extension of the capillary tube 20 spaced apart from the counter electrode and the working electrode.

As shown in FIG. 5, which is a modification of the thread in FIG. It can be placed almost flat with the bottom surface of the toilet fat section. In this example, the capillary 2o itself is not required. Working, counter and reference electrodes are matrix It is in contact with an electrolyte impregnated inside.

FIG. 6 is a block diagram of an electrochemical measurement system using potential control. reference electrode, The working and counter electrodes are all connected to a potentiostat, which The stat is connected to an integrator and a waveform generator.

The sensor structure and electrical parameters are interrelated. one parameter The total change in parameters (e.g. electrode surface roughness) and other parameters, e.g. What effect does it have on the time at the position and the potential sweep speed for measuring adsorbed species? It is possible to predict qualitatively.

By using these qualitative correlation characteristics, we can calculate the A value for each lζ parameter is selected.

(ii) in equilibrium with the gas being fiii) have an appropriate conductivity; and (1v) that interferes with the regeneration of the adsorbed species involved or unduly suppresses it. The platinum electrode should not be strongly adsorbed to the surface of other electrodes. for example , in the case of a sensor for carbon dioxide, a sensor containing salt or not containing salt (e.g., 0. 1 μm H2S04), phosphate buffer and dilute potassium bicarbonate containing Na2SO4 can be selected as the supporting electrolyte.

, the temporal response (also related to membrane properties), and several sets of electrical parameters. Accuracy of charged current measurement, influence of oxygen and response to charged current However, it is possible to minimize the peak current. This surface roughness coefficient is approximately 1 ．． 5 (smooth electrode can be varied between 1 and 1000 or more. Good, smooth surface The roughness coefficient is between approximately 1.5 and 200.

(C1 diaphragm A dihydrophobic diaphragm allows external fluid (gas or liquid) to be connected to the electrolysis behind the diaphragm. (internal electrolyte), and the internal electrolyte is removed from the external fluid. Can be isolated automatically. If the sensor is made “diaphragm limited” , the permeability of the diaphragm is important in determining the measurement current or load IM, IJi current. Po Polytetrafluoroethylene is currently the preferred membrane material. (Other suitable abductions) Materials include silicones and polypropylene. ) Carbon dioxide permeability of diaphragm can be varied by changing thickness, porosity or chemical composition. .

2. Electrical parameters A number of signal forms are input to the potentiostat to generate adsorbed species, and this generated Electrolytic oxidation of adsorbate and periodic cleaning of the platinum surface from contamination by incidental impurities Can be purified. In the present case, it is preferred that the sensor If a trapezoidal waveform as shown in FIG. 7 can be used.

Referring to Figure 7 for a particular waveform, if we consider a single cycle (solid line), The adsorption potential (Eads) (keep tads and Eads constant) and time ( tads). This adsorbate is oxidized during the anodic potential ramp (AR). The current is accumulated between this sloped part, and the amount of adsorbent produced and the amount of oxidized peak The effects of current or peaks at constant potential within the circuit are affected. Purification potential (F2 ct), the accumulated impurities Iri are removed from the electrode surface during time (tct), and the negative! It is directly converted by chemisorbed oxygen which is reduced during the ramping (CR). This selected The most important parameters in the waveform are Eads, ta, ds and the slope of the anode tilt. be. Eads are selected such that adsorbed species are easily generated.

As an example, Eads −+ for a reversible hydrogen mold in the same electrolyte for CO2 measurement. A reference value of 7Q mV can be used.

At this potential, the reduction and absorption of carbon dioxide is rapid and the generation of hydrogen gas is minimal.

The saturation of the electrode by the adsorbed species is known ([for reduced CO2, the actual surface area of the electrode 1 (corresponds to a charging current of approximately 0.2 mC0'lt per tyn"), so the initial adsorption The selection of time is easily made and varies with the surface roughness coefficient of the electrode used. sensor Another variable is the permeability of the diaphragm. In a “diaphragm-only” sensor, the The amount of nitrogen-absorbing substances produced in a given period of time depends on the permeability of the diaphragm.

The selection of the slope of the slope AR is such that it (1) oxidizes all adsorbed species for a reasonable time and (11 ) The adsorbate is oxidized at a potential high enough to minimize the activation amount and cause Pt-0 formation. and minimize ohmic polarization between the sensing electrode and the counter electrode. It is done as follows. The value of the slope of AR depends on the surface roughness coefficient, typically l VO], varies from t/Sec to 10 mV/5ec-4, and this range is l 1 second to about 1.5 minutes for the slope of the volt. The purification potential ('Ecz) is It is between 1 volt and 1,5 volt. The time tC4 at KcL is a single molecule The layer is selected to produce substantially chemisorbed oxygen. Including this purification step is not required. This is because purification or activation at high potentials occurs in many cycles. This is because it is needed only after the Kuru. Moreover, reversal from AR to CR is suitable. When carried out at a moderate potential (e.g., 5 volts), electrode purification is Occurs during the delicious potential of. The waveform without the purification step is shown in FIG. cathodic tilt The value of the slope depends on the surface degree coefficient and the time of the cleaning phase.

Figure 9 shows waveforms in another embodiment with potential gradients at the anode and cathode, and the potential of the cathode gradient. The step is to reduce the Pt-0 film and measure the oxygen concentration of the fluid being measured almost simultaneously. It's no good.

Figure 10 shows a constant potential pulse that can be used to further reduce pt-oy platinum. A modified waveform is shown that allows for substantially simultaneous measurement of the oxygen concentration of the fluid being measured.

In addition to the use of potential control methods as described above, galvanostatic (constant or controlled) Modifications including controlled voltages, ) pulses are available. (These changes All shapes produce chemisorbed species in amounts that depend only on the partial pressure of the gas being measured. It is. ) For example, the adsorbed species is generated at a constant potential stage of shield 1 constant value and fixed time. The measurement pattern of the galvanostat is as shown schematically in the block diagram of FIG. The constant potential adsorption pulp can be made to follow the constant potential adsorption pulp. (Actually, the port Connect the tensionostat internally to switch from potentiostat mode to galvanostat mode. You can switch to ``nod'' mode. ) Galvanostat Hals (Fixed value ) The electrode potential hourly curve obtained during phase A) in which the current flow rate is proportional to the amount of adsorbed species for a fixed current.

After this adsorbent oxidation step, the potential increases and oxidizes the electrode surface (see Figure 11). Phase B) (equal to a purge pulse). Required to coat platinum surface with chemisorbed oxygen After a certain period of time, the operation mode is changed to potential control mode and the adsorption nozzle starts again. Ru. By partially changing this method, oxygen was measured almost simultaneously as shown in Figure 11p. can do. According to this method, adsorbate is generated at a constant potential, followed by The measurement of adsorbed species and the oxidation of the platinum surface are carried out at a constant current, and then the operating mode is controlled. The side leg potential mode is changed by applying a control potential pulse, and this control potential pattern In the pulse, the oxygen reduction current is measured after a period of this pulse. From now on, this The cycle is repeated.

Multiple gases (e.g., CO1CO2, NO4, H2S, a2.-j-al vapor, Hydrocarbons, etc.) are also treated with Rubanostano, as shown in the block diagram in Figure 12. It can be measured using only the standard method. According to this method, Garkukunostat is Connected through a switch to both the working and counter electrodes is a recorder and an integrator. Or connected to a timer.

The electroactive building absorbs N (partial reduction) between a constant current and an initial current flow for a certain period of time. Chemically at once by straining or oxidation, or non-electrochemically by chemisorption. ), and the ridges were oxidized as described above. Ru. After the purification step, the current is then reversed to effect reduction of the platinum oxidized surface. . Between this stage comes the stage of adsorption η5y, as shown in the figure.゛ Contains Mw in combination with potential measurement. In this method, purification, inversion, or stereotaxic When the pulse is given, the platinum oxide is reduced and an electroactive adsorbent is generated when the pulse is given. be done.

(high current), adsorbate is generated. After this, the amount of adsorbed species is determined by the open circuit potential associated with this amount (as shown in Figure 13). ) by measuring the appropriate potential using the sensor discussed above. The oxygen content in a fluid can be measured by measuring the oxygen reduction current at Ru. This oxygen measurement measures electric current, and the coexisting reactive gas does not become electroactive. Gas concentration measurements are performed at low potentials and are sensitive to acid The elementary measurements do not interfere with gas partial pressure measurements. Then, oxygen absorbs nitrogen and generates chloric acid. Even if the oxygen is reduced at each potential, the effect of the current due to oxygen reduction is It is small compared to the size of the overflow flow caused by the oxidation of chemisorbed N species. Pg The suitability of the above method for measuring a8 and PO2 almost simultaneously but independently depends on the electrodes. It depends on the surface roughness coefficient and the permeability of the diaphragm.

Oxygen measurements can be improved by changing the waveform. therefore, Using the trapezoidal waveform shown in Figure 8 as a reference, the CR can measure oxygen. By introducing a waiting time at a constant potential (above the range of carbon dioxide reduction potentials) You can change it.

During the surface active adsorption produced on the sensor and electrode provided according to the present invention Multimm (7) based on measurement of the amount of adhesion on the ridge! (flJ, Co, Co2, H 2S, 7 Alcohol vapor, hydrocarbons, etc.) The method for determining the amount requires high sensitivity. have In addition to being miniaturized, this sensor is ion-selective and solid. Has electrodes with little or no shear as experienced with constant element electrodes . Therefore, this electrode has unique performance in cases where measurement accuracy is an essential condition. Ru.

The sensor's internal calibration, which takes into account packground and surface area changes, Q, O with charge or current that is unrelated and depends on the electrode surface area and is entwined with Siemo curves. It can be done instrumentally by dividing X. .

Other variations within the scope of the concepts opened herein may be made as recognized by those skilled in the art. You can do something like that.

Engraving (no changes to the content) cl Procedural amendment February 27, 1980 Kazuo Wakasugi, Official of the Patent Office 1.Display of the incident 2. Name of the invention Muttai sensor and its usage 5. Date of written amendment order: February 14, 1980 International search report

Claims (1)

[Claims] 1. To measure the amount of electroactive absorbed MW related to gas attached to the electrode surface. Hence the method of measuring the concentration of said gas in a fluid. 2. According to claim 1, the electrode contains a platinum group metal and gold. the method of. 3. The method according to claim 2, wherein the platinum group metal is platinum. 4. The method according to claim 2, wherein the platinum group metal is a platinum alloy. Law. 5. The method according to claim 2, wherein the fluid is a liquid. 6. The method according to claim 2, wherein the fluid is a mixed gas. 7. Generated on the electrode surface by applying a well-defined potential (one current) A method of measuring the concentration of gas in a fluid by measuring the amount of suction. 8. The method of claim 7, wherein the electrode comprises a platinum group metal. 9. The method according to claim 8, wherein the platinum group metal is platinum. 10. The platinum group metal according to claim 8, wherein the platinum group metal is a platinum alloy. Method. 3 11. The method of claim 8, wherein the fluid is a liquid. 12. (Transfer A+ gas from the fluid onto the electrode surface as a suction rod, (Bl suction rod) A method of measuring the concentration of a gas in a fluid by measuring the amount of . 13. Claim 12, characterized in that the electrode contains a platinum group metal and gold. Method described. 1/4. The method according to claim 13, which includes an electrode purification step. Law. 15. Control the tA1 stage and fB1 stage with a potentiostat, and 14. A method according to claim 13, characterized in that the current flowing between them is multiplied. 16. Measuring the oxygen content of the fluid substantially simultaneously and independently (including the C1 stage) 16. A method according to claim 15, characterized in that: 17. claim 12, characterized in that: The method described in section. 18, including a te1 stage for substantially simultaneously and independently measuring the oxygen content of the fluid; 18. A method according to claim 17, characterized in that: 19, (The entire feature is that the A1 stage and tB1 stage are controlled by carbanostat. The method according to claim 13. 20. Measuring oxygen content almost simultaneously and independently (including C1 stage) 20. The method of claim 19. 21, the fA) phase occurs at the control potential, the fB) phase occurs at the open circuit potential, and this open circuit The method is characterized in that it measures the road potential and correlates it with the amount of adsorption produced. Scope of Request The method described in item 13. 22, the +A1 stage occurs at a constant current, the (B) stage occurs at an open circuit potential, and this opening The feature is that the path potential is measured and correlated with the amount of absorbed NE"JiO produced. Claim 13r (a method according to claim 13. (b) Gas and liquid impermeable housing means in which the housing has an opening therein; and a working electrode and at least one at least one portion within the housing and spaced apart from each other. a counter electrode, an electrolyte in contact with each electrode, and an electrolyte in contact with the opening within the housing. A gas is brought into contact with the working electrode from the fluid under test by being present across the mouth. a gas-permeable hydrophobic diaphragm through which the gas can pass, and an adsorption rod on the working electrode. and includes means for measuring the potential or current of the working electrode. a means for controlling the gas concentration in the fluid under test; body sensor. 24. Claims characterized in that a reference electrode is also included within the housing. Gas sensor according to paragraph η. 6. Claim No. 6, characterized in that the hydrophobic diaphragm is a fluorocarbon polymer. Gas sensor described in paragraph (B). 26. Claim 23, characterized in that it is a hydrophobic diaphragm or a silicone diaphragm. Gas sensors as described in Section. 27. Claim 23, characterized in that the hydrophobic diaphragm is polyzolopyrene. Gas sensor described in. 41. The gas according to claim n, characterized in that the working electrode contains platinum and gold. body sensor. 29. A gas sensor characterized in that the diaphragm is made of a fluorinated hydrocarbon polymer. 30. The electrolyte is a substantially free electrolyte, and the working electrode is a reference electrode and a counter electrode. 29. The air according to claim 29, characterized in that the air body sensor 31, an electrolyte is impregnated in a matrix, and the working electrode and the counter electrode are connected to each other; Claim 29, characterized in that the poles are in contact with the matrix. In the gas sensor scale-032, the reference electrode is far away from the working electrode and the counter electrode. The electrolyte-impregnated matrix and the liquid are connected to each other through an electrolyte reservoir 7 containing electrolyte g. 32. The gas sensor according to claim 31, wherein the gas sensor is in contact. 33, an electrolyte is retained within the matrix and the working electrode, counter electrode and reference electrode Each of the poles is in contact with the matrix, and the hydrophobic diaphragm is in contact with the matrix. 29. The gas cell according to claim 29, wherein the gas cell is in contact with the opposing surface of the gas cell. Sir. 34, comprising a sensor consisting of at least a working electrode and a counter electrode; Each said electrode is connected to a current source or potential controller, which controller is a current integrator. by connecting the two reductively adsorbed onto the working electrode of the sensor. It is characterized by measuring carbon oxide as a function of the partial pressure of carbon dioxide. A system for measuring the concentration of carbon dioxide in a test fluid. 35. The sensor is connected to a potentiostat, and the potentiostat is connected to an applied potential waveform generator and a current integrator. The system according to Range 34. 36. The method according to claim 35, wherein the sensor includes a reference electrode. The system listed. 37. The sensor connects to the galvano stand and potentiostat via a switch. and the potentiostat is connected to an applied potential waveform generator. 35. System according to claim 34, characterized in that: The sensor is connected to a galvano stand and an integrator via a switch, Claim characterized in that the sensor includes a reference electrode connected directly to the integrator. The system according to paragraph 34. 39.A device for detecting and measuring gas, which includes (1) At least 5% of the active material is in contact with the external body by means of a hydrophobic diaphragm. (2) producing a repeatable transient potential action for a total duration of less than 5 minutes; The potential of the working electrode is controlled so that the action causes the total generation of gas-derived adsorbate. including at least the potential area of the dam and the potential area of the dam for measuring the adsorption bud. the means and (3) A device consisting of a means for measuring the amount of absorbent material.