CN104792836A - Method for detecting electrically neutral gas by electric potential type sensor based on ion selective electrode and device thereof - Google Patents

Abstract

The invention relates to a potentiometric sensor for detecting electrically neutral gas, in particular to a method and a device for detecting electrically neutral gas with a potential sensor based on an ion-selective electrode. Molecularly imprinted polymers are used as the recognition material for selective electrically neutral gas molecules. The recognition material is dispersed in the sensitive membrane of the polymer membrane ion-selective electrode. After the polymer membrane ion-selective electrode absorbs gas molecules in the gas phase, it uses The organic ions with similar chemical structures of electrically neutral gas molecules are used as indicator ions to indicate the selective recognition process between the imprinted polymer in the polymer film phase and the electrically neutral gas molecules to be measured, so as to realize the identification of electrically neutral gas molecules. Potential detection. The detection method of the invention realizes the direct molecular recognition of the ion-selective electrode of the polymer membrane to the neutral gas molecule in the gas phase, further realizes the potential detection of the neutral gas, and broadens the application range of the ion-selective electrode.

Description

A method and device for detecting an electrically neutral gas with a potentiometric sensor based on an ion-selective electrode

technical field

The invention relates to a potentiometric sensor for detecting electrically neutral gas, in particular to a method and a device for detecting electrically neutral gas with a potential sensor based on an ion-selective electrode.

Background technique

Polymer membrane ion-selective electrodes are an important branch of chemical sensors. Since the late 1990s, this type of electrode has become a new hot spot in the field of chemical sensors and has been widely used in whole blood, serum, urine, tissue, intracellular Direct determination of various electrolyte ions in liquid and its dilution. In terms of gas detection, in recent years, researchers at home and abroad have developed a variety of ion-selective electrodes for detecting gases, and some of them have been commercialized, such as ammonia gas-sensing electrodes, hydrogen sulfide gas-sensing electrodes, sulfur oxide gas-sensing electrodes and nitrogen gas-sensing electrodes. Oxide gas sensitive electrodes, etc. The detection principle of these gas-sensing electrodes is to use the influence of gas on a certain chemical balance to change the activity of a specific ion in the balance, and then use ion-selective electrodes to measure the change in the activity of the specific ion in the solution phase, thereby Measure the concentration of the measured gas. It should be pointed out that the currently developed gas-sensing electrodes based on ion-selective electrodes can only measure gases that can be dissolved in water and hydrolyzed in the solution (such as ammonia NH ₃ →NH ₄ ⁺ ). Solvent gas molecules such as toluene, formaldehyde and acetone are difficult to detect.

The detection of electrically neutral molecules by ion-selective electrode potentiometry has long been a challenge, because the prerequisite for the potential response of the electrode is that the analyte must be a charged ion. Recently, we have achieved potentiometric detection of electrically neutral organic molecules using ion-selective electrode technology. The developed potentiometric method for detecting electrically neutral organic molecules is only for the detection of electrically neutral molecules in the solution phase, and the research on the potential detection of electrically neutral gas molecules in the gas phase has not yet been carried out. At the same time, the selective recognition process of all potentiometric sensors based on ion-selective electrodes is carried out in the solution phase, and the research on using this type of sensor to realize direct molecular recognition in the gas phase has not been reported in the literature.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the existing analysis technology, and provide a method and device for detecting electrically neutral gas based on an ion-selective electrode-based potentiometric sensor.

To achieve the above object, the technical solution adopted in the present invention is:

A method for detecting electrically neutral gases with a potentiometric sensor based on an ion-selective electrode. Molecularly imprinted polymers are used as the identification material for selective electrically neutral gas molecules, and the identification material is dispersed in the sensitive membrane of the polymer membrane ion-selective electrode. In this method, after the polymer membrane ion-selective electrode adsorbs gas molecules in the gas phase, organic ions with similar chemical structures to the electrically neutral gas molecules are used as indicator ions to indicate that the imprinted polymer in the polymer membrane phase has the same electrical neutrality as that to be measured. The selective recognition process between gas molecules enables the potential detection of electrically neutral gas molecules.

Specifically:

a. Molecularly imprinted polymers with specific recognition capabilities for electrically neutral gas molecules are used as molecular recognition materials for polymer membrane ion-selective electrodes, so that they constitute ion-selective electrodes based on molecularly imprinted polymer sensitive membranes ;

b. inserting the ion-selective electrode obtained in step a into an indicator ion measuring cell having a structure similar to that of the gas molecule to be measured, to generate a control potential change signal;

c. placing the ion-selective electrode obtained in step a in a gas collector containing electrically neutral gas molecules for enrichment, and then transferring the ion-selective electrode obtained in step a into a measuring cell containing an indicator ion solution, Generate a standard potential change signal;

d. The standard working curve is obtained by plotting the concentration of the neutral gas with the control and the standard potential change;

e. Place the ion-selective electrode obtained in step a in the gas sample containing the gas to be measured for enrichment, and then transfer the ion-selective electrode obtained in step a into the measuring cell containing the indicator ion to generate a sample potential change Signal; the concentration of the electrically neutral gas to be measured can be obtained by comparing with the standard working curve.

The electrically neutral gas molecules are benzene, toluene, xylene, chlorobenzene, dichlorobenzene, dinitrotoluene, acetonitrile, chloroform, n-heptane, cyclohexane, trichloroethane, tetrahydrofuran, ethyl acetate, Gaseous molecules of N,N-dimethylformamide, trichloroethylene, formaldehyde, acetone, methanol, ethanol, isopropanol, n-butanol, or isobutanol.

The indicator ion is an organic ion having a similar chemical structure to the electrically neutral gas molecule to be measured, for example, the indicator ion of the toluene gas molecule is benzoic acid ion.

Preparation of the sensitive membrane of the polymer membrane ion-selective electrode: polymer matrix material, plasticizer, molecularly imprinted polymer particles and ion exchanger in parts by weight ratio of 20-40:40-80:0.2-20 : 0.1-10 mixed, then blended into tetrahydrofuran solution, stirred to make it evenly mixed, and then volatilized naturally at room temperature to obtain a polymer sensitive film.

The polymer matrix material is polyvinyl chloride, polybutyl acrylate, polybutyl acrylate, polyetherimide, rubber, sol-gel film; the plasticizer is o-nitrophenyloctyl ether (o-NPOE ), di-2-ethylhexyldecyl ester, dibutyl sebacate, dioctyl sebacate; the ion exchanger is the cation exchanger tetrakis(3,5-di(trifluoromethyl)phenyl)boronic acid Sodium or anion exchanger dinonylnaphthalenesulfonic acid or tridodecylammonium chloride.

The molecularly imprinted polymer particles are mixed with electrically neutral gas template molecules, functional monomers and cross-linking agents at a molar ratio of 1:1-10:1-100, then adding 5-100ml porogen, and ultrasonicating for 10 minutes. Thermally initiate polymerization at 50-100°C for 1-24 hours in the presence of an initiator to obtain a white blocky polymer. The obtained polymer is continuously and repeatedly eluted with an elution solvent for 2 hours each time until the eluent is no longer visible in the ultraviolet absorption spectrum. Until the absorption peak, the molecularly imprinted polymer is obtained.

The functional monomer is acrylic acid, methacrylic acid, acrylamide, 2,6-diaminopyridine, 2-vinylpyridine, 4-vinylpyridine or 4-vinylphenylboronic acid; alcohol dimethacrylate or divinylbenzene; the porogen is benzene, toluene, acetonitrile, chloroform, tetrahydrofuran or methanol; the initiator is 2,2'-azobisisobutyronitrile, 2,2 '-azobisisobutyronitrile or 2,2'-azo-bis(2,4-dimethylvaleronitrile); the eluent is methanol and acetic acid (v/v, 1/1～9/ 1).

A special device for the method of detecting an electrically neutral gas based on an ion-selective electrode potentiometric sensor, the special device includes a gas generator 1, a gas collector 5, a detection cell 6, an ion-selective electrode 7, a reference electrode 8 and PXSJ-216L ion meter 10; gas generator 1 includes a gas carrier device 2 and a liquid storage device 4, wherein the gas carrier device 2 and the liquid storage device 4 are connected through a pipeline A, and the connection between the liquid storage device 4 and the gas collector 5 A pipeline C is connected in parallel between the pipeline A between the gas carrier device 2 and the liquid storage 4 and the pipeline B between the liquid storage 4 and the gas collector 5; the ion selective electrode 7 and the reference electrode 8 are respectively connected to the PXSJ-216L ion meter 10 through wires; the ion-selective electrode 7 is first inserted into the gas collector 5 to absorb gas and then inserted into the detection cell 6; the bottom of the ion-selective electrode 7 is provided with a polymer sensor film9.

Flowmeters 3 are provided on the pipeline A between the gas carrier device 2 and the liquid storage 4 and on the pipeline C, respectively.

The pipeline A between the gas carrier device 2 and the liquid storage 4 is inserted under the liquid level of the liquid storage 4; the pipeline B between the liquid storage 4 and the gas collector 5 is inserted into the liquid storage 4 liquid surface.

Detection principle: Molecularly imprinted polymers have the characteristics of predetermined structure and activity, specific recognition and wide practicability, and have been widely used in the field of analytical chemistry. Molecularly imprinted technology integrates the characteristics of separation and enrichment, which can improve the selectivity and sensitivity of analysis; molecularly imprinted polymers have strong stability and can resist the harsh environment of detection, so molecularly imprinted polymers are polymer membrane ion Ideal ionophores for selective electrodes in complex matrix detection applications. In addition, molecularly imprinted polymers can not only realize the selective separation and enrichment of analytes in the solution phase, but also can be used as gas adsorbents to achieve highly selective adsorption of gas molecules in the gas phase. In view of this, the present invention firstly synthesizes an electrically neutral gas molecularly imprinted polymer, and disperses it as an ionophore in the polymer membrane ion-selective electrode sensitive membrane, and then places the obtained electrode in a gas phase gas sample to absorb the electrically neutral gas Finally, the adsorbed electrode is inserted into the indicator ion solution containing the chemical structure similar to the gas to be measured, and the indicator gas molecule selectively recognizes the imprinted polymer in the membrane phase, thereby realizing the determination of the neutral gas molecule.

The advantages of the present invention are:

1. The potential sensor for detecting electrically neutral gas molecules of the present invention effectively solves the difficult problem that the traditional electrode potential method is difficult to detect electrically neutral gas molecules, broadens the application field of ion selective electrodes, and will effectively promote the application of chemical sensor technology in the environment Monitor developments in the field.

2. The present invention realizes the direct recognition of gas molecules in the gas phase by the polymer membrane ion selective electrode for the first time, and provides a certain theoretical reference for the analysis and application of the ion selective electrode technology in the gas phase.

3. The present invention uses highly selective molecularly imprinted polymers as the selective recognition carrier of the electrically neutral organic gas molecules to be measured, and selects organic ions having a similar structure to the electrically neutral gas molecules as the signal indicating the ion conduction potential, and then A potentiometric sensor for detecting electrically neutral gas molecules is obtained. The present invention uses ion-selective electrodes to detect electrically neutral gas molecules, avoids the use of large-scale chromatographic analysis instruments, greatly reduces detection costs, and makes quantitative on-site monitoring of gas pollutants possible. Therefore, the present invention will be used in atmospheric monitoring and environmental analysis. , pollutant control and other fields play a huge role.

Description of drawings

Fig. 1 is a schematic diagram of a detection device for detecting electrically neutral gas with a potentiometric sensor based on an ion selective electrode provided by an embodiment of the present invention. Among them, 1. Gas generator, 2. Carrier gas, 3. Flow meter, 4. Liquid storage, 5. Gas collector, 6. Detection cell, 7. Ion selective electrode, 8. Reference electrode, 9. Polymer sensitive membrane, 10.PXSJ-216L ion meter.

Fig. 2 is the control potential signal response curve of the electrode without the adsorption of toluene gas molecules to the indicator ion provided by the embodiment of the present invention and the standard potential response signal of the electrode enriched with different concentrations of toluene gas molecules.

Fig. 3 is a standard working curve for measuring toluene gas molecules with different concentrations by the electrode provided by the embodiment of the present invention.

Detailed ways

Example 1

Take the detection of toluene gas, an electrically neutral gas molecule, as an example. The specific detection steps are as follows:

a. Preparation of toluene molecularly imprinted polymer:

Take 4mmol of methacrylic acid, 10mmol of divinylbenzene and 30mg of azobisisobutyronitrile dissolved in 30mL of porogen toluene, oscillate ultrasonically for 5min, and blow nitrogen gas for deoxygenation for 15min. The reaction vessel was sealed under a nitrogen atmosphere, then transferred to an oil bath, and reacted at 60° C. for 12 hours to obtain white solid particles. The obtained white solid particulate polymer was vacuum-dried at 70°C, and fully eluted with methanol-acetic acid (V/V=9/1) solution to remove template molecules. The white solid granular polymer was repeatedly washed with methanol to remove residual acetic acid, and dried at 70° C. for 24 hours to obtain toluene MIP.

b. Electrode preparation:

Accurately weigh 360mg 2.8wt% toluene molecularly imprinted polymer, 31.9wt% polyvinyl chloride particles, 51.0wt% o-nitrophenyloctyl ether, 12.8wt% polyethylene glycol and 1.5wt% tris(dodecyl) Ammonium chloride, add 3.5mL tetrahydrofuran, ultrasonic, stir for 2h to disperse evenly. Pour the membrane components into a glass ring with an inner diameter of 3.6 cm, and volatilize in a constant temperature dryer at 25°C for 12 hours. After the tetrahydrofuran is completely volatilized, a molecularly imprinted polymer sensitive membrane is obtained. At this time, the thickness of the membrane is about 200 μm. The obtained sensitive membrane was cut into circular slices with a diameter of 6 mm using a hole punch, and adhered to the top of a polyvinyl chloride tube with tetrahydrofuran. Before using the electrode, use 1/30M phosphate buffer solution (pH=8.0) as the flushing solution and activation solution for activation for 24 hours.

c. Insert the electrode into the measuring cell of the phosphate buffer solution containing 2×10 ^-4 mol/L benzoate anion as the indicator ion to generate a control potential signal;

Insert the electrode into a series of different concentrations of toluene gas for enrichment for 30 minutes (toluene gas concentration is 10, 50, 75, 100, 125, 150ppm respectively), and then transfer the electrode to a gas containing 2×10 ^-4 mol/L as In the measuring cell of the phosphate buffer solution of the benzoate anion of indicator ion, produce standard potential signal (referring to Fig. 2); Described phosphate buffer solution concentration is 1/30mol/L, and pH value is 8.0;

d. get the standard working curve (as shown in Figure 3) to the toluene gas concentration plotting with reference and standard potential rate of change;

e. Insert the electrode into the gas collector containing the gas sample to be tested for enrichment for 30 minutes, and then transfer the electrode to the phosphate buffer solution containing 2×10 ^-4 mol/L benzoate anion as the indicator ion In the measuring cell, a sample potential signal is generated; by comparing with the standard working curve, the concentration of the toluene gas to be measured can be obtained.

Electrode performance: the electrode of the present invention can be within the concentration range of 10-125ppm, the initial potential change rate of the electrode is linearly related to the concentration of toluene gas, and the detection limit is about 3.3ppm (3σ). Here, the initial potential change rate of the electrode is defined as the first-order fitting of the potential versus time when the initial potential change is within the range of less than 5 mV.

Detection device: Electrically neutral gas detection device (see Figure 1) includes gas generator 1, gas collector 5, detection cell 6, ion selective electrode 7, reference electrode 8 and PXSJ-216L ion meter 10; gas generator 1 includes a gas carrier device 2 and a liquid storage device 4, wherein the gas carrier device 2 and the liquid storage device 4 are connected through a pipeline A, and the liquid storage device 4 and the gas collector 5 are connected through a pipeline B. A pipeline C is connected in parallel on the pipeline A between the device 2 and the liquid storage 4 and the pipeline B between the liquid storage 4 and the gas collector 5; the ion-selective electrode 7 and the reference electrode 8 pass through the wire and the gas collector respectively. The PXSJ-216L ion meter 10 is connected; the ion selective electrode 7 is first inserted into the gas collector 5 to absorb gas and then inserted into the detection cell 6; the bottom of the ion selective electrode 7 is provided with a polymer sensitive membrane 9. Flowmeters 3 are respectively provided on the pipeline A between the gas carrier device 2 and the liquid storage 4 and on the pipeline C. The pipeline A between the gas carrier device 2 and the liquid storage 4 is inserted under the liquid level of the liquid storage 4; the pipeline B between the liquid storage 4 and the gas collector 5 is inserted into the liquid storage 4 liquid surface.

The ion-selective electrode 7 is filled with a 1/30M phosphate buffer solution. The reference electrode 8 is a double-junction saturated calomel electrode.

Example 2

Take the detection of the concentration of the electrically neutral gas toluene in the air by the present invention as an example.

Take an air sample, measure the potential change rate signal according to steps c, d and e in Example 1, refer to the standard working curve, and compare the sample signal in the air with the standard working curve to obtain the gas concentration of the electrically neutral gas toluene in the air.

Example 3

Take the detection of the concentration of electrically neutral gas toluene in industrial waste gas by the present invention as an example.

Take an industrial waste gas sample, measure the potential change rate signal according to steps c, d and e in Example 1, refer to the standard working curve, and compare the sample signal in the air with the standard working curve to obtain the gas concentration of the electrically neutral gas toluene in the air.

Example 4

Take the detection of the formaldehyde gas concentration of the electrically neutral gas in the air by the present invention as an example.

a. Preparation of formaldehyde molecularly imprinted polymer:

Except that the porogen is replaced by formaldehyde solution, the remaining implementation steps are carried out with reference to step a of Example 1;

b. Electrode preparation:

Except that the indicator ion is replaced by formic acid, the other implementation steps are carried out with reference to step b of Example 1;

Detection of formaldehyde gas concentration of electrically neutral gas in the air: according to steps c, d and e of Example 1, referring to the standard working curve, and comparing the sample signal in the air with the standard working curve, the concentration of formaldehyde gas in the air can be obtained.

Example 5

Take the detection of the formaldehyde gas concentration of the electrically neutral gas in the air by the present invention as an example.

a. Preparation of formaldehyde molecularly imprinted polymer:

Except that the porogen is replaced by formaldehyde solution, the remaining implementation steps are carried out with reference to step a of Example 1;

b. Electrode preparation:

Except that the indicator ion is replaced by formic acid, the other implementation steps are carried out with reference to step b of Example 1;

Detection of formaldehyde gas concentration of electrically neutral gas in the air: according to steps c, d and e of Example 1, referring to the standard working curve, and comparing the sample signal in the air with the standard working curve, the concentration of formaldehyde gas in the air can be obtained.

Example 6

Take the detection of the xylene gas concentration of the electrically neutral gas in the air by the present invention as an example.

a. Preparation of xylene molecularly imprinted polymers:

Except that the porogen is replaced by xylene solution, the remaining implementation steps are carried out with reference to step a of Example 1;

b. Electrode preparation:

Except that the indicator ion is replaced by p-toluic acid, the remaining implementation steps are carried out with reference to step b of Example 1;

Detection of the xylene gas concentration of the electrically neutral gas in the air: according to steps b, c and d of Example 1, referring to the standard working curve, and comparing the signal of the sample in the air with the standard working curve, the concentration of the xylene gas in the air can be obtained.

Claims (6)

1. A method for detecting an electrically neutral gas based on an ion-selective electrode-based potentiometric sensor, characterized in that: a molecularly imprinted polymer is used as the identification material for selective electrically neutral gas molecules, and the identification material is dispersed in the polymer membrane ion In the sensitive membrane of the selective electrode, after the polymer membrane ion-selective electrode adsorbs gas molecules in the gas phase, organic ions with similar chemical structures to the electrically neutral gas molecules are used as indicator ions to indicate the imprinted polymer in the polymer membrane phase. The selective recognition process between the electric neutral gas molecule and the electric neutral gas molecule to be measured, so as to realize the potential detection of the electric neutral gas molecule. 2. the method for detecting electrically neutral gas based on the potentiometric sensor of ion selective electrode according to claim 1, is characterized in that: a. Molecularly imprinted polymers with specific recognition capabilities for electrically neutral gas molecules are used as molecular recognition materials for polymer membrane ion-selective electrodes, so that they constitute ion-selective electrodes based on molecularly imprinted polymer sensitive membranes ; b. inserting the ion-selective electrode obtained in step a into an indicator ion measuring cell having a structure similar to that of the gas molecule to be measured, to generate a control potential change signal; c. placing the ion-selective electrode obtained in step a in a gas collector containing electrically neutral gas molecules for enrichment, and then transferring the ion-selective electrode obtained in step a into a measuring cell containing an indicator ion solution, Generate a standard potential change signal; d. The standard working curve is obtained by plotting the concentration of the neutral gas with the control and the standard potential change; e. Place the ion-selective electrode obtained in step a in the gas sample containing the gas to be measured for enrichment, and then transfer the ion-selective electrode obtained in step a into the measuring cell containing the indicator ion to generate a sample potential change Signal; the concentration of the electrically neutral gas to be measured can be obtained by comparing with the standard working curve. 3. according to the method that the potentiometric sensor based on ion selective electrode described in claim 1 or 2 detects electrically neutral gas, it is characterized in that: described electrically neutral gas molecule is benzene, toluene, xylene, chlorobenzene, Dichlorobenzene, dinitrotoluene, acetonitrile, chloroform, n-heptane, cyclohexane, trichloroethane, tetrahydrofuran, ethyl acetate, N,N-dimethylformamide, trichloroethylene, formaldehyde, acetone, Gaseous molecules of methanol, ethanol, isopropanol, n-butanol, or isobutanol. 4. a kind of special device based on the method for the potential type sensor of ion selective electrode to detect electric neutral gas according to claim 1, it is characterized in that: special device comprises gas generator (1), gas collector (5) , detection cell (6), ion selective electrode (7), reference electrode (8) and PXSJ-216L ion meter (10); gas generator (1) includes carrier gas device (2) and liquid reservoir (4 ), wherein the gas carrier device (2) is connected to the liquid reservoir (4) through a pipeline A, and the liquid reservoir (4) is connected to the gas collector (5) through a pipeline B, and the gas carrier device ( 2) A pipeline C is connected in parallel with the pipeline A between the liquid storage (4) and the pipeline B between the liquid storage (4) and the gas collector (5); the ion selective electrode (7) and The reference electrode (8) is respectively connected to the PXSJ-216L ion meter (10) through wires; the ion selective electrode (7) is first inserted into the gas collector (5) to absorb gas and then inserted into the detection cell (6); the ion selective A polymer sensitive film (9) is provided at the bottom of the electrode (7). 5. The special device for the method for detecting electrically neutral gas based on the potentiometric sensor of ion-selective electrode according to claim 4, characterized in that: between the carrier gas device (2) and the liquid reservoir (4) Flow meters (3) are respectively arranged on the pipeline A and the pipeline C. 6. The special device for the method for detecting electrically neutral gas based on the potentiometric sensor of ion-selective electrode according to claim 4, characterized in that: between the carrier gas device (2) and the liquid reservoir (4) The pipeline A is inserted under the liquid surface of the liquid storage (4); the pipeline B between the liquid storage (4) and the gas collector (5) is inserted on the liquid surface of the liquid storage (4).