TWI436055B - An electrochemical sensing electrode and a method for detecting the concentration of hydrogen peroxide in the solution to be measured - Google Patents

Description

Electrochemical sensing electrode and method for detecting hydrogen peroxide concentration of liquid to be tested

The invention relates to an electrochemical sensing electrode and a method for detecting the concentration of hydrogen peroxide, in particular to an electrochemical sensing electrode comprising a sensing film containing polybenzimidazole, and an application containing A method for detecting a hydrogen peroxide concentration of a liquid to be tested by an electrochemical sensor of the sensing electrode.

In the method of electrochemically detecting hydrogen peroxide, the sensing electrodes used are mainly classified into an enzyme electrode and a non-enzymatic electrode. Although the enzyme electrode is highly selective, it still has the following disadvantages: it is necessary to consider enzyme activity during preparation, and it is easy to reduce enzyme activity and poor stability with environmental changes or use time. However, the existing non-enzymatic electrode is mainly based on the oxidation potential, and the oxidation potential is easy to cause other non-test substances to undergo oxidation reaction at the same time, so that the detection result is disturbed, so that the non-enzymatic electrode is applied to the electrochemical sensor in the subsequent application. It is less specific.

No. 5,320,725 discloses an electrode for detecting hydrogen peroxide, the electrode comprising an electrode having a test surface and a conversion film covering the test surface. The conversion film includes a crosslinked redox polymer network and a peroxidase which is bonded to the crosslinked redox polymer network. The mechanism for detecting hydrogen peroxide in this patent is: (1) oxidizing peroxidase to obtain an oxidized peroxidase; (2) subjecting the oxidized peroxidase to the crosslinked redox polymer network Reduction, obtaining an oxidized crosslinked redox polymer network; (3) finally electrochemically reducing the oxidized crosslinked redox Subnetted to detect the required current value. The peroxidase is mainly derived from an enzyme, and the crosslinked redox polymer network is mainly a transition metal complex containing an organic ligand. This patent requires the use of special peroxidase and cross-linked redox polymer network, and the peroxidase still has the disadvantage of instability, so it can not effectively extend the life of the electrode.

It can be seen from the above that the sensing electrodes currently used for detecting hydrogen peroxide still have many disadvantages that need to be improved, among them, the stability and service life of the electrodes, and the sensitivity and specificity required for subsequent application to the electrochemical sensor. The nature is even more urgent and needs to be further improved.

Accordingly, it is an object of the present invention to provide an electrochemical sensing electrode that has good stability, can be effectively extended in service life, is simple to fabricate, and can be subsequently applied to an electrochemical sensor.

Another object of the present invention is to provide a method for detecting the concentration of hydrogen peroxide in a liquid to be tested having specificity and good sensitivity.

Thus, the electrochemical sensing electrode of the present invention comprises: a conductor; and a sensing film covering the conductor, wherein the sensing film contains polybenzimidazole.

The method for detecting a hydrogen peroxide concentration of a liquid to be tested comprises: placing the liquid to be tested and an organic acid in an electrochemical sensor, wherein the electrochemical sensor comprises the electrochemical sensing electrode Causing a portion of the nitrogen atom on the polybenzimidazole contained in the sensing film of the sensing electrode to be oxidized; and providing a fixed potential to the electrochemical sensor to cause the sensing film of the sensing electrode to be The oxidized polybenzimidazole is reduced, and the required current value is measured, and the hydrogen peroxide concentration of the test solution is calculated from a standard curve of the current and the hydrogen peroxide concentration.

The sensing electrode of the present invention is obtained by coating a conductive film containing polybenzimidazole on the conductor. Polybenzimidazole has good thermal stability, chemical and environmental stability and mechanical properties, so it is extremely stable during use, making the sensing electrode have a long service life. The method of the present invention oxidizes a portion of the nitrogen atoms of the polybenzimidazole on the sensing film by using an electrochemical sensor comprising the above-described sensing electrode with stability, and mainly by the following mechanism:

Organic acid + hydrogen peroxide contained in the test solution → → peroxyacid + water

Peroxyacid + polybenzimidazole → → oxidized polybenzimidazole + acid is oxidized, and the oxidized polybenzimidazole on the sensing film of the sensing electrode is reduced by a constant potential method. At the same time, the required current is measured, and finally the hydrogen peroxide concentration contained in the liquid to be tested is calculated from the standard curve of the current and the concentration of hydrogen peroxide. The method of the invention does not need to consider the influence of the environment, and because the detection is performed under the reduction potential, the interference of other substances other than the liquid to be tested can be avoided, and a more precise hydrogen peroxide concentration can be obtained.

Preferably, the polybenzimidazole contained in the sensing film has a repeating unit represented by the following formula (I) or (II):

In each of the repeating units represented by the formula (I), X ¹ represents a tetravalent aromatic group which may form a benzimidazole ring with a nitrogen atom at both ends of two adjacent carbon atoms; R ¹ and R ² represent Hydrogen or an alkyl group having a carbon number ranging from 1 to 12; Y ¹ represents a single bond, a divalent aromatic group having a carbon number ranging from 2 to 20, a divalent aliphatic group having a carbon number ranging from 2 to 20, or a carbon number range a divalent alicyclic group of 2 to 20; and n1 = 10 to 1000; and in each of the repeating units represented by the formula (II), X ² represents a trivalent aromatic group which forms a benzimidazole ring with a nitrogen atom. R ³ represents hydrogen or an alkyl group having a carbon number ranging from 1 to 12; Y ² represents a single bond, a divalent aromatic group having a carbon number ranging from 2 to 20, and a divalent aliphatic group having a carbon number ranging from 2 to 20. Or a divalent alicyclic group having a carbon number ranging from 2 to 20; and n2 = 10 to 1000.

Preferably, the polybenzimidazole is represented by the formula (I), and the X ¹ is represented by the formula:

R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁶ each represent hydrogen or a halogen.

Preferably, Y ^{1 of} the formula (I) represents a single bond, a methylene group, an ethylene group, a propylene group, a butylene group, and a pentylene group. ), hexylene, vinylene, propenylene, butenylene, hexenylene, cyclohexylene, cyclohexene (cyclohexenylene), phenylene, pyridylene, furanylene, pyridinium Pyrazylene, pyranylene or thiophenylene.

Preferably, the polybenzimidazole is represented by the formula (II), and the X ² is represented by the formula:

R ¹⁷ , R ¹⁸ and R ¹⁹ each represent hydrogen or a halogen.

Preferably, Y ^{2 of} the formula (II) represents a single bond, a methyl group, a methyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a vinyl group, a propylene group, and a butyl group. Alkenyl, hexenylene, cyclohexyl, cyclohexene, phenyl, pyridyl, furyl, pyridine A thiol or a thienyl group.

In one embodiment of the invention, the polybenzimidazole is represented by the formula: (n=10~1000, hereinafter abbreviated as " PBI "); in another embodiment of the present invention, the polybenzimidazole is represented by the following formula:

(R ¹ and R ² each represent hydrogen or butyl, m = 10 to 1000, and the name is "poly(N-butylbenzimidazole), hereinafter abbreviated as " PBBI ").

Preferably, the sensing film further contains polyacrylic acid.

When the sensing film is composed of polybenzimidazole and polyacrylic acid, the ratio of polybenzimidazole to polyacrylic acid can be adjusted according to actual needs, but it should be noted that the sensing film needs to be oxidized. A sufficient amount of polybenzimidazole. Preferably, the sensing film has a molar ratio of polybenzimidazole to polyacrylic acid ranging from 0.05 to 2.9.

Preferably, the sensing film further comprises an acid-modified carbon nanotube.

When the sensing film is composed of polybenzimidazole and acid-modified carbon nanotubes, the ratio of polybenzimidazole to acid-modified carbon nanotubes can be adjusted according to actual needs, but It is noted that the sensing film needs to contain a sufficient amount of polybenzimidazole that can be oxidized. Preferably, the weight ratio (wt/wt) of the polybenzimidazole to the acid-modified carbon nanotube of the sensing film ranges from 0.3 to 24.

Preferably, the acid-modified carbon nanotube is a carbon nanotube having a plurality of acid groups on the surface, and the acid group is -COOH or -(C=O)-X-COOH, and X is selected from An alkylene group having a carbon number ranging from 1 to 8, an alkenyl group having a carbon number ranging from 2 to 8, an alkyl group substituted with an alkyl group having at least one carbon number ranging from 1 to 8, and an unsubstituted phenyl group. An anthranyl group substituted with an alkyl group having at least one carbon number ranging from 1 to 8, or an unsubstituted naphthyl group.

The electrochemical sensing electrode of the present invention can be prepared in a known manner, for example, by first formulating polybenzimidazole into a solution, applying it to a conductor, and finally drying. The electrochemical sensing electrode of the invention is simple to manufacture, and the use of the extremely stable polybenzimidazole makes the life and stability of the sensing electrode greatly improved.

In the method for detecting the hydrogen peroxide concentration of a liquid to be tested according to the present invention, the organic acid may be any organic acid which can be oxidized, particularly an organic acid which can be oxidized with hydrogen peroxide. Preferably, the organic acid is acetic acid.

The electrochemical sensor used in the method of the present invention can be assembled in accordance with known electrochemical sensors, in addition to having to include the electrochemical sensing electrodes described above. Preferably, the electrochemical sensor further comprises a counter electrode, a reference electrode, a buffer and an ammeter.

Preferably, the fixed potential provided to the electrochemical sensor ranges from 0.2V to -0.6V.

The method of the invention can eliminate the interference of the non-test substance and improve the detection sensitivity and specificity by using the electrochemical sensing electrode and adding the selected potential to the reduction potential.

The present invention will be further illustrated by the following examples, but it should be understood that this embodiment is intended to be illustrative only and not to be construed as limiting.

<Example> [Example 1]

0.23 g (7.47 × 10 ^-4 mol) of PBI was dissolved in 50 mL of dimethyl hydrazine, and after completely dissolved, it was concentrated to 10 mL under reduced pressure to obtain a solution. 2 μL of the solution was uniformly dropped on the surface of a gold electrode (surface area of 0.196 cm ² ), and dried at 50 ° C for 5 hours to prepare a sensing electrode of Example 1 (the conductor was a gold electrode, and the outer layer was coated One layer of PBI ).

[Embodiment 2]

The fabrication process and conditions were the same as in Example 1 except that " PBI " was replaced with " PBBI " and the volume of dimethyl hydrazine was adjusted to 10 mL. Finally, the sensing electrode of Example 2 was prepared. It is a gold electrode, and its outer layer is covered with a layer of PBBI] .

[Example 3]

0.06 g (1.95 x 10 ^-4 mol) of PBI was dissolved in 10 mL of dimethyl sulfoxide to obtain a PBI solution. 0.1 g (1.39 x 10 ^-3 mol) of polyacrylic acid (available from SHOWA, molecular weight range 8000 to 12000) was dissolved in 10 mL of dimethyl hydrazine to obtain a polyacrylic acid solution. 100 μL of the PBI solution was mixed with 320 μL of a polyacrylic acid solution [PBI : polyacrylic acid molar ratio of 0.07] to obtain a mixed solution.

1 μL of the mixture was uniformly dropped on the surface of a gold electrode (surface area of 0.196 cm ² ), and dried at 50 ° C for 5 hours to prepare a sensing electrode of Example 3 (the conductor was a gold electrode, and the outer layer thereof A coating comprising a mixture of polybenzimidazole and polyacrylic acid).

[Example 4]

0.06 g (1.95 x 10 ^-4 mol) of PBI was dissolved in 10 mL of dimethyl sulfoxide to obtain a PBI solution. 0.01 g of the acid-modified carbon nanotube (prepared by the inventor of the present invention to purchase a pure carbon tube and then modified with an acid) was dissolved in 10 mL of dimethyl sulfoxide to obtain a nanometer. Carbon tube solution. 100 μL of the PBI solution was mixed with a 1000 μL carbon nanotube solution (weight ratio of PBI to acid-modified carbon nanotubes of 0.6) to obtain a mixed solution.

150 μL of the mixture was evenly dropped on the surface of a gold electrode (surface area of 0.196 cm ² ), and dried at 50 ° C for 5 hours to prepare a sensing electrode of Example 4 (the conductor was a gold electrode, and the outer layer was wrapped. A coating comprising a mixture of polybenzimidazole and acid modified carbon nanotubes).

[test]

The sensing electrodes of the above Examples 1 to 4 and a counter gold electrode were respectively placed in a 40 mL phosphate buffer solution (pH=7.0), and then a wire was used to connect the sensing electrode to an ammeter and another wire was used. The electrochemical electrodes of Examples 1 to 4 were prepared by connecting the opposite electrode and the ammeter.

Next, the following tests were performed using the electrochemical sensors of Examples 1 to 4, respectively:

1. The effect of acetic acid usage:

According to the amount of acetic acid used in Table 1 below, different amounts of acetic acid were dropped into the electrochemical sensor, and then the potential was fixed at -0.5 V and the current value was stabilized. After being continuously stabilized for 150 seconds, according to the concentration detection range of the aqueous hydrogen peroxide solution in Table 1 below, different concentrations of hydrogen peroxide solution were dropped into the electrochemical sensor every 30 seconds, and finally changed with time. The current value changes are recorded separately to produce a current-time graph, wherein the response time is an average of the time required from each step to the next step in the graph, and the response time is preferably as short as possible. Then, the "current value" and the "hydrogen peroxide concentration" are made into a linear graph, wherein the sensitivity is the ratio of the slope of the linear graph to the surface area of the electrode. The lowest detection concentration is obtained by separately adding different lower concentrations of hydrogen peroxide solution to the electrochemical sensor and observing the lowest concentration at which the current can change. The results obtained are summarized in Table 1 below.

From the results of Table 1, it can be found that the electrochemical sensors of Examples 1 to 4 have a response time range of 2.2 to 11.3 sec, a sensitivity range of 1.9 to 569.4 μA/mM ‧ cm ^{2 ,} and a minimum detection concentration range of 6.25 to 75.00. μM, which proves that the electrochemical sensor of the present invention can produce different current changes with changes in the concentration of hydrogen peroxide, and is very suitable for detecting hydrogen peroxide.

From the results of Nos. 1-1~1-3 and 2-2~2-3, it can be found that when the amount of acetic acid used is increased, the response time can be shortened, but the sensitivity is lowered. It can be seen that the amount of acetic acid used affects the electrochemical sense. The sensitivity of the detector is therefore optimal for fixing the amount of acetic acid used during the test.

Comparing the results of Nos. 1-1, 2-1, 3-1, and 4-1, it was found that the result of 4-1 was the best, and it was found that when the conductor surface was coated with polybenzimidazole and acid-modified Nye When the carbon nanotubes are used, they have better response time, sensitivity and minimum detection temperature. In addition, the results of 1-1 and 2-1 show that poly(nitrogen-butylbenzimidazole) results are poor, and it is obvious that when the nitrogen of polybenzimidazole is substituted by a substituent, it will affect electrochemical sensing. Response time and sensitivity of the device.

2. Interference test:

0.1 mL of acetic acid was added to the electrochemical sensors of Examples 1 to 4, respectively, and then the potential was fixed at -0.5 V and the current value was stabilized. After continuing to stabilize for 150 seconds, a hydrogen peroxide solution having a concentration of 1 mM was added. After the current is equilibrated, different concentrations of interfering substances (0.1 mM vitamin C, 0.1 mM uric acid, 1.0 mM vitamin C, 1.0 mM uric acid) are continuously instilled every 30 seconds, and the current changes are observed. The results are shown in Fig. 9 The curve in ~12 is shown in (a).

From the results of the curve (a) of FIGS. 9 to 12, it can be seen that there is no significant change in the current after the addition of the interfering substance, and it can be considered that there is almost no interference phenomenon, thereby further demonstrating the specificity of the electrochemical sensor of the present invention. It will not be affected by interfering substances.

3. Oxidant interference test:

In order to test whether the oxidant reacts with the material of the electrode surface and generates a current change to affect the detection of hydrogen peroxide, 0.1 mL of acetic acid is added to the electrochemical sensors of Examples 1 to 4, respectively, and then the potential is fixed. -0.5V and stabilize the current value. After continuing to stabilize for 150 seconds, a hydrogen peroxide solution having a concentration of 1 mM was added. After the current was equilibrated, red blood salt phosphate buffer (produced by mixing red blood salt and phosphate buffer) at a concentration of 0.1 mM and 1.0 mM was continuously added every 30 seconds to observe the current change. As shown in the curve (b) in Figures 9-12.

From the results of the curve (b) of Figures 9 to 12, it is known that there is no significant change in current after the addition of the oxidant, which proves that the oxidant does not oxidize with the material of the electrode surface (such as polybenzimidazole), so it does not affect Detection of hydrogen peroxide.

In summary, the electrochemical sensing electrode of the present invention has the advantages of good stability and long service life because it comprises a sensing film containing polybenzimidazole. The method for detecting the hydrogen peroxide concentration of the liquid to be tested according to the present invention can effectively detect the hydrogen peroxide concentration under the influence of the undisturbed substance and the oxidant by using an electrochemical sensor including the above-mentioned sensing electrode. Meet the industry's response time, sensitivity and minimum detection concentration.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent.

1 is a current-time graph illustrating the current change of the electrochemical sensor of Example 1 after adding 0.1 mL of acetic acid and different concentrations of hydrogen peroxide solution, wherein the in-line pattern is current-hydrogen peroxide. a linear graph of concentration;

2 is a current-time graph illustrating the current change of the electrochemical sensor of Example 1 after adding 0.5 mL of acetic acid and different concentrations of hydrogen peroxide solution, wherein the in-line pattern is current-hydrogen peroxide. a linear graph of concentration;

3 is a current-time graph illustrating the current change of the electrochemical sensor of Example 1 after adding 2.0 mL of acetic acid and different concentrations of hydrogen peroxide solution, wherein the embedded pattern is current-hydrogen peroxide. a linear graph of concentration;

4 is a current-time graph illustrating the current change of the electrochemical sensor of Example 2 after adding 0.1 mL of acetic acid and different concentrations of hydrogen peroxide solution, wherein the in-line pattern is current-hydrogen peroxide. a linear graph of concentration;

Figure 5 is a current-time graph illustrating the current change of the electrochemical sensor of Example 2 after adding 0.5 mL of acetic acid and different concentrations of hydrogen peroxide solution, wherein the inline pattern is current-hydrogen peroxide a linear graph of concentration;

6 is a current-time graph illustrating the current change of the electrochemical sensor of Example 2 after adding 2.0 mL of acetic acid and different concentrations of hydrogen peroxide solution, wherein the in-line pattern is current-hydrogen peroxide. a linear graph of concentration;

7 is a current-time graph illustrating the current change of the electrochemical sensor of Example 3 after adding 0.1 mL of acetic acid and different concentrations of hydrogen peroxide solution, wherein the in-line pattern is current-hydrogen peroxide. a linear graph of concentration;

Figure 8 is a current-time graph illustrating the current change of the electrochemical sensor of Example 4 after adding 0.1 mL of acetic acid and different concentrations of hydrogen peroxide solution, wherein the in-line pattern is current-hydrogen peroxide a linear graph of concentration;

9 is a current-time graph illustrating the results of the interference test and the oxidant interference test of the electrochemical sensor of Example 1, wherein the curve (a) is the result of the interference test and the curve (b) is the oxidant interference test. the result of;

10 is a current-time graph illustrating the results of the interference test and the oxidant interference test of the electrochemical sensor of Example 2, wherein the curve (a) is the result of the interference test and the curve (b) is the oxidant interference test. the result of;

11 is a current-time graph illustrating the results of the interference test and the oxidant interference test of the electrochemical sensor of Example 3, wherein the curve (a) is the result of the interference test and the curve (b) is the oxidant interference test. Result; and

12 is a current-time graph illustrating the results of the interference test and the oxidant interference test of the electrochemical sensor of Example 4, wherein the curve (a) is the result of the interference test and the curve (b) is the oxidant interference test. the result of.

Claims (10)

An electrochemical sensing electrode for detecting a hydrogen peroxide concentration of a liquid to be tested, the electrochemical sensing electrode comprising: a conductor; and a sensing film covering the conductor, wherein the sensing film a polybenzimidazole and an acid-modified carbon nanotube, the acid-modified carbon nanotube is a carbon nanotube having a plurality of acid groups on the surface, and the acid group is -(C=O)- X-COOH, X is an exo-alkyl group selected from the group consisting of an alkylene group having a carbon number ranging from 1 to 8, an alkenyl group having a carbon number ranging from 2 to 8, and an alkyl group substituted with an alkyl group having at least one carbon number ranging from 1 to 8. A non-substituted phenyl group, an extended naphthyl group substituted with at least one alkyl group having a carbon number of 1 to 8, or an unsubstituted naphthyl group. The electrochemical sensing electrode according to claim 1, wherein the polybenzimidazole has a repeating unit represented by the following formula (I) or the following formula (II): In each of the repeating units represented by the formula (I), X ¹ represents a tetravalent aromatic group which may form a benzimidazole ring with a nitrogen atom at both ends of two adjacent carbon atoms; R ¹ and R ² represent Hydrogen or an alkyl group having a carbon number ranging from 1 to 12; Y ¹ represents a single bond, a divalent aromatic group having a carbon number ranging from 2 to 20, a divalent aliphatic group having a carbon number ranging from 2 to 20, or a carbon number range a divalent alicyclic group of 2 to 20; n1 = 10 to 1000; and in each of the repeating units represented by the formula (II), X ² represents a trivalent aromatic group which forms a benzimidazole ring with a nitrogen atom. R ³ represents hydrogen or an alkyl group having a carbon number ranging from 1 to 12; Y ² represents a single bond, a divalent aromatic group having a carbon number ranging from 2 to 20, and a divalent aliphatic group having a carbon number ranging from 2 to 20. Or a divalent alicyclic group having a carbon number ranging from 2 to 20; and n2 = 10 to 1000. The electrochemical sensing electrode according to claim 1, wherein the weight ratio of the polybenzimidazole to the acid-modified carbon nanotube of the sensing film ranges from 0.3 to 24. The electrochemical sensing electrode according to claim 1, wherein the polybenzimidazole is represented by the formula (I), and the X ¹ is represented by the following formula: R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁶ each represent hydrogen or a halogen. The electrochemical sensing electrode according to claim 4, wherein Y ^{1 of} the formula (I) represents a single bond, a methyl group, a methyl group, a propyl group, a butyl group, and a pentyl group. , hexyl, vinyl, propylene, butylene, hexenylene, cyclohexyl, cyclohexene, phenyl, pyridyl, furan, pyridine A thiol or a thienyl group. The electrochemical sensing electrode according to claim 1, wherein the polybenzimidazole is represented by the formula (II), and the X ² is represented by the following formula: R ¹⁷ , R ¹⁸ and R ¹⁹ each represent hydrogen or a halogen. The electrochemical sensing electrode according to claim 6, wherein Y ^{2 of} the formula (II) represents a single bond, a methyl group, a methyl group, a propyl group, a butyl group, and a pentyl group. , hexyl, vinyl, propylene, butylene, hexenylene, cyclohexyl, cyclohexene, phenyl, pyridyl, furan, pyridine A thiol or a thienyl group. A method for detecting a concentration of hydrogen peroxide in a liquid to be tested, comprising: placing the liquid to be tested and an organic acid in an electrochemical sensor, wherein the electrochemical sensor contains a patent application scope The electrochemical sensing electrode according to any one of items 1 to 7, wherein the sensing electrode comprises a sensing film, the sensing film comprises polybenzimidazole; and the sensing film of the sensing electrode is included a portion of the nitrogen atom on the polybenzimidazole is oxidized; and providing a fixed potential to the electrochemical sensor to reduce the oxidized polybenzimidazole of the sensing film of the sensing electrode, and measuring the The current value is required, and the hydrogen peroxide concentration of the liquid to be tested is calculated from a standard curve of the current and the hydrogen peroxide concentration. The method of claim 8, wherein the organic acid is acetic acid. The method of claim 8, wherein the fixed potential ranges from 0.2 V to -0.6 V.