Method for measuring content of isoniazide by using carbon quantum dots

Abstract

The invention discloses a method for determining the content of isoniazide (INH) through carbon quantum dots (CQDs), and belongs to the technical field of isoniazide content determination. Fluorescence of the carbon quantum dots is quenched under the oxidation action of potassium permanganate, on the basis of oxidation-reduction reaction, the carbon quantum dots react with isoniazide with reducibility, a fluorescence value is recovered, and quantitative detection is carried out. According to the method, firstly, a standard curve is established according to the linear relation between increase of the fluorescence intensity difference value delta F of a system after isoniazide is added and the concentration of isoniazide, and the content of isoniazide in an isoniazide sheet sample is measured according to the standard curve. The invention provides a simple, convenient, rapid and accurate new method for measuring the content of isoniazide, and also expands the application range of the carbon quantum dots.

Description

Technical Field

[0001] The invention belongs to the technical field of isoniazid content determination, and more particularly relates to a method for determining isoniazid content using carbon quantum dots. Background Art

[0002] Tuberculosis (TB) is a common and potentially fatal infectious disease caused by Mycobacterium tuberculosis (TB). It is primarily transmitted through the respiratory tract and is more common in adults, particularly those with malnutrition or HIV infection. Isoniazid, along with rifampicin, ethambutol, pyrazinamide, and streptomycin, is a first-line anti-TB drug and plays a crucial role in the treatment of TB. Isoniazid (INH) is an effective anti-TB drug that effectively controls various types of TB, including those affecting the lungs, lymph nodes, bones, kidneys, intestines, meningitis, and peritonitis, and effectively prevents the development of drug resistance. Therefore, it is often used in combination with other first-line anti-TB drugs. INH can be used for prophylaxis in people who have contact with patients with active pulmonary TB. It also has other effects, such as antidepressant and antibacterial properties. It is often the first drug prescribed for patients with drug-susceptible TB and, in many cases, is the fastest way to save a patient's life. Therefore, accurately measuring the INH content in tablets is crucial for guiding clinical medication use, developing appropriate treatment plans, and ensuring safe and effective drug use.

[0003] Isoniazid, one of the most effective first-line drugs for treating various forms of pulmonary tuberculosis, is widely used worldwide, and a variety of methods are available for its determination. Currently reported methods for isoniazid determination include capillary electrophoresis with electrochemical detection, electrochemical methods, titration, ultraviolet spectroscopy, high-performance liquid chromatography, and gas chromatography. Each of these measurement methods has its own advantages and disadvantages. For example, some methods have reduced accuracy and detection precision, while others offer higher accuracy and precision. However, these methods are only suitable for macro-analysis and not for trace components, and are not widely adopted. Therefore, the development of new methods for the sensitive, accurate, and rapid determination of isoniazid is necessary. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for determining the content of isoniazid (INH) using carbon quantum dots (CQDs) to solve the problems existing in the above-mentioned prior art and to achieve sensitive, accurate and rapid determination of isoniazid.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention is to provide an application of carbon quantum dots in determining the isoniazid content in isoniazid tablets.

[0007] The second technical solution of the present invention: provides the application of carbon quantum dots in fluorescence detection of isoniazid content in isoniazid tablets.

[0008] The third technical solution of the present invention is to provide a method for determining the content of isoniazid using carbon quantum dots, comprising the following steps:

[0009] Preparation of standard curve: The mixed solution of carbon quantum dot solution and potassium permanganate standard solution was used as the control group T3, and the mixed solution of isoniazid standard solution, carbon quantum dot solution and potassium permanganate standard solution with a series of concentrations was used as the test group T4. The fluorescence intensity F T3 And the fluorescence intensity F of the test group T4 T4 , then calculate ΔF=F T4 -F T3 , then make a standard curve with isoniazid concentration as the horizontal axis and ΔF as the vertical axis;

[0010] Determination of isoniazid content: a mixed solution of carbon quantum dot solution and potassium permanganate standard solution was used as the control group T1, and a mixed solution of isoniazid sample solution, carbon quantum dot solution and potassium permanganate standard solution was used as the test group T2. The fluorescence intensity F of the control group T1 was measured respectively. T1 And the fluorescence intensity F of the test group T2 T2 , then calculate ΔF=F T2 -F T1 ; Substitute ΔF into the standard curve to calculate the isoniazid concentration.

[0011] Preferably, the concentration of isoniazid in the isoniazid standard solution of the series of concentrations is 0.25×10 -3 ~2×10 - 3 mol / L; the standard curve is y=285.55x+239.25, R 2 =0.9959, the detection limit is 2.6×10 -5 mol / L.

[0012] Preferably, the volume ratio of the carbon quantum dot solution and the potassium permanganate standard solution in the control group T3 is 4:1.5; the volume ratio of the isoniazid standard solution of the series of concentrations, the carbon quantum dot solution and the potassium permanganate standard solution in the test group T4 is 2:4:1.5.

[0013] Preferably, the volume ratio of the carbon quantum dot solution and the potassium permanganate standard solution in the control group T1 is 4:1.5; the volume ratio of the isoniazid sample solution to be tested, the carbon quantum dot solution and the potassium permanganate standard solution in the test group T2 is 2:4:1.5.

[0014] Preferably, the conditions for measuring the fluorescence intensity are: a wavelength of 397 nm; and each mixed solution is reacted at a pH of 7 and a temperature of 30° C. for 15 minutes before measuring the fluorescence intensity.

[0015] Preferably, the steps of preparing the carbon quantum dot solution include: mixing starch, ethylenediamine and water and then heat-treating to obtain a dark brown solution, filtering, fixing the filtrate to 100 mL, and diluting 50 times before use;

[0016] The usage ratio of the starch, ethylenediamine and water is 8g:3mL:10mL.

[0017] Preferably, the step of preparing the isoniazid sample solution to be tested comprises: dissolving the isoniazid sample to be tested in water and fixing the volume to 100 mL to obtain the isoniazid sample solution to be tested.

[0018] Preferably, the concentration of the potassium permanganate standard solution is 1×10 -3 mol / L.

[0019] The present invention discloses the following technical effects:

[0020] (1) The carbon quantum dots of the present invention are prepared by using starch and ethylenediamine, and the preparation process is simple and the required reaction conditions are mild.

[0021] (2) The present invention utilizes the oxidizing effect of potassium permanganate to quench the fluorescence of carbon quantum dots, and on the basis of the redox reaction, reacts with isoniazid having reducing properties to restore the fluorescence value for quantitative detection. The present invention first conducts preliminary experiments to determine the dosage of each reagent and selects the appropriate wavelength, and then mainly discusses the conditions for determining the isoniazid content using the carbon quantum dot method. A standard curve is established by utilizing the linear relationship between the increase in the fluorescence intensity difference ΔF of the system after adding isoniazid and the isoniazid concentration, and the isoniazid content in the isoniazid tablet sample is determined based on the standard curve. The present invention provides a simple, rapid and accurate new method for the determination of isoniazid content, and also expands the application range of carbon quantum dots (CQDs). BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The results of the amount of carbon quantum dot solution selected in Example 1;

[0023] Figure 2 The result of the dosage selection of potassium permanganate standard solution described in Example 1;

[0024] Figure 3 The fluorescence spectra of the solutions described in Example 1 are shown in FIG.

[0025] Figure 4 This is a graph showing the effect of pH on ΔF described in Example 2;

[0026] Figure 5 This is a graph showing the effect of reaction time on ΔF described in Example 2;

[0027] Figure 6 This is a diagram showing the effect of temperature on ΔF described in Example 2;

[0028] Figure 7 This is the standard curve described in Example 3. DETAILED DESCRIPTION

[0029] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0030] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0031] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0032] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0033] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0034] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0035] The following instruments and reagents are used in the following examples of the present invention:

[0036] Table 1 Experimental instruments

[0037] instrument company F97Pro Fluorescence Spectrophotometer Shanghai Lingguang Technology Co., Ltd. analytical balance Shanghai Sunny Hengping Scientific Instrument Co., Ltd. Chinese LCD Ultrasonic Cleaner Kunshan Meimei Ultrasonic Instrument Co., Ltd. Electronic constant temperature stainless steel water bath Shanghai Yichang Instrument Screen Factory

[0038] Table 2 Experimental reagents

[0039] Reagents company starch Tianjin Jindong Tianzheng Fine Chemical Reagent Factory Ethylenediamine Hengyang Kaixin Chemical Reagent Co., Ltd. concentrated hydrochloric acid Chengdu Jinshan Chemical Reagent Co., Ltd. Sodium hydroxide Tianjin Hengxing Chemical Reagent Manufacturing Co., Ltd. potassium permanganate Hengyang Kaixin Chemical Reagent Co., Ltd. Isoniazid standard Beijing Inokai Technology Co., Ltd. Sample isoniazid tablets Hangzhou Minsheng Pharmaceutical Co., Ltd.

[0040] Synthesis of carbon quantum dot solution: Weigh 8 g of starch and add it to a 50 mL polytetrafluoroethylene reactor. Add 3 mL of ethylenediamine and 10 mL of ultrapure water, and heat at a constant temperature of 180 ° C for 18 h. Cool the reactor to room temperature to obtain a dark brown solution. After coarse filtration through filter paper, filter it through a microporous membrane filter with a pore size of 0.22 μm. The filtrate is made up to volume in a 100 mL volumetric flask and diluted 50 times before use.

[0041] Preparation of standard solution:

[0042] Hydrochloric acid standard solution: Accurately pipette 0.84 mL of concentrated hydrochloric acid into a 100 mL volumetric flask, add distilled water to make up to volume to prepare a 0.1 mol / L standard solution for use.

[0043] Sodium hydroxide standard solution: Prepare a dry small beaker, accurately weigh 0.4g of sodium hydroxide powder and add it to it, add an appropriate amount of distilled water, stir with a glass rod to dissolve it completely, and then transfer it to a 100mL volumetric flask. Wash the small beaker and glass rod 2-3 times, inject the washing liquid into the volumetric flask, and adjust the volume to obtain 0.1mol / L sodium hydroxide solution. Then accurately transfer 1mL of sodium hydroxide solution to a 100mL volumetric flask and add distilled water to adjust the volume to obtain 1×10 -3 mol / L standard solution.

[0044] Potassium permanganate standard solution: Prepare a dry small beaker, accurately weigh 0.0158g of potassium permanganate powder and add it to it, and add appropriate amount of distilled water. Stir it with a glass rod to dissolve it completely, then transfer it to a 100mL volumetric flask, wash the small beaker and glass rod 2-3 times, inject the washing solution into the volumetric flask, and dilute to obtain 1×10 - 3 mol / L standard solution.

[0045] Isoniazid standard solution: prepare a dry small beaker, accurately weigh 0.0137g of isoniazid powder and add it to it, and add appropriate amount of distilled water, stir with a glass rod to completely dissolve it, wash the small beaker and glass rod 2 to 3 times, inject the washing solution into a volumetric flask, and then transfer it to a 100mL volumetric flask and dilute to obtain 1×10 -3 mol / L standard solution.

[0046] Example 1

[0047] This example provides the preliminary experiment to verify whether the method of the present invention is feasible and to select the optimal measurement wavelength, carbon quantum dot solution and potassium permanganate standard solution dosage, as follows:

[0048] Wavelength selection:

[0049] The prepared carbon quantum dot solution can be observed to be yellow in color. First, start the fluorescence spectrophotometer and preheat it for 15 minutes. Place the quartz cuvette filled with the solution and wiped clean on all four sides into the sample chamber, close the lid, set the excitation wavelength to 300nm, and scan the carbon quantum dot solution in the emission wavelength range of 300-780nm. It was found that the strongest peak was at 475nm. Then, under the condition of an emission wavelength of 475nm, the excitation spectrum of the solution in the range of 200-450nm was scanned, and a peak was found at 397nm. Therefore, the excitation wavelength of 397nm and the emission wavelength of 475nm were selected for subsequent experiments.

[0050] Selection of the dosage of carbon quantum dot solution:

[0051] Measure the fluorescence intensity of 0.5-4 mL of the fixed volume carbon quantum dot solution. Prepare several clean 10 mL stoppered colorimetric tubes, add 0.5, 1, 1.5, 2, 3, and 4 mL of carbon quantum dot solution to different colorimetric tubes, and shake them to 10 mL. Then measure the fluorescence intensity of each system. When the amount of CQDs is 4 mL, the fluorescence intensity of the solution is higher than 2000. At this time, the solution has a higher fluorescence intensity (such as Figure 1 As shown), 4 mL of carbon quantum dot solution was selected for subsequent experiments.

[0052] Selection of dosage of potassium permanganate standard solution:

[0053] Measure and add 0.5~3mL 1×10 -3 mol / L potassium permanganate standard solution, prepare several clean 10mL stoppered colorimetric tubes, add 4mL of carbon quantum dot solution to each stoppered colorimetric tube, then add 0.5, 1, 1.5, 2, and 3mL of potassium permanganate solution to different colorimetric tubes, make the volume to 10mL and shake well, then measure the fluorescence intensity of each system, and find that when the amount of potassium permanganate standard solution is 1.5mL, the fluorescence value of the system drops below 700, and the fluorescence intensity of the solution is obviously quenched (such as Figure 2 As shown in the figure, it meets the experimental requirements, so 1.5mL potassium permanganate standard solution is selected for subsequent experiments.

[0054] When 2 mL of 1×10 -3mol / L isoniazid standard solution, the fluorescence intensity after recovery was higher than 1200, which shows that the fluorescence intensity has recovered significantly. Therefore, 2mL of isoniazid standard solution was selected for subsequent experiments.

[0055] Verify the feasibility of the method described in the present invention: test the fluorescence spectra of carbon quantum dot solution, 4mL carbon quantum dot solution + 1.5mL potassium permanganate (KMnO4) standard solution, 4mL carbon quantum dot solution + 1.5mL potassium permanganate (KMnO4) standard solution + 2mL isoniazid (INH) standard solution, and the results are as follows Figure 3 shown.

[0056] Figure 3 1 is the fluorescence spectrum of each solution described in Example 1.

[0057] Depend on Figure 3 It can be seen that the maximum fluorescence intensity of the three curves is at λ ex / λ em =397 / 475nm. By comparing the fluorescence spectra of each solution, it can be found that the carbon quantum dots themselves have a high fluorescence intensity. After adding potassium permanganate, the fluorescence intensity is significantly quenched. After adding isoniazid, the fluorescence intensity of the system is significantly restored. This preliminarily proves that this method can be used to determine the isoniazid content.

[0058] Example 2

[0059] This example verifies the effects of parameters such as pH value, reaction time, and reaction temperature on ΔF during the determination of isoniazid content, as follows:

[0060] Effect of pH value:

[0061] Dilute 0.1 mol / L hydrochloric acid solution 100 times to obtain 1×10 -3 moL / L hydrochloric acid solution for later use. Prepare several clean 10mL stoppered colorimetric tubes, place them on a test tube rack, set up six control groups and six test groups, and accurately add 4mL of carbon quantum dot solution and 1.5mL of potassium permanganate standard solution to all colorimetric tubes in turn. Select three colorimetric tubes in the control group and add 1mL, 0.1mL, and 0.01mL of prepared hydrochloric acid solution, and add 0.01mL, 0.1mL, and 1mL of sodium hydroxide solution to the other three colorimetric tubes, all of which are diluted to 10mL and shaken well; in addition to adding the same reagents as the control group, the six colorimetric tubes in the test group are all added with 2mL of isoniazid standard solution, diluted to 10mL and shaken well, and then reacted at 30℃ for 5min, and the maximum fluorescence intensities F1 and F2 of the control group solution and the test group solution are recorded, their difference ΔF=F2-F1 is calculated, and the correlation curve between pH and ΔF is drawn, as shown below: Figure 4 shown.

[0062] Figure 4 This is the effect of pH on ΔF as described in Example 2. Figure 4 It can be seen that when the pH is 7, ΔF is the maximum, so pH 7 is selected for the following experiments.

[0063] Effect of reaction time:

[0064] A control group and a test group were established. 4 mL of carbon quantum dot solution and 1.5 mL of potassium permanganate standard solution were added to two 10 mL stoppered colorimetric tubes in sequence as the control solution. 2 mL of isoniazid standard solution was added to one of the colorimetric tubes as the test solution. The volumes were fixed and the solution was shaken gently to allow the reaction to complete. The fluorescence intensity was measured at different time points (5, 15, 25, 35, 45, 55, 65, and 75 min) of the reaction. The maximum fluorescence intensity F1 of the control group solution and the maximum fluorescence intensity F2 of the test group solution were measured, and their ΔF=F2-F1 was calculated. A correlation curve diagram of the reaction time change and ΔF was prepared, as shown in FIG. Figure 5 shown.

[0065] Figure 5 This is a graph showing the effect of reaction time on ΔF as described in Example 2. Figure 5 It can be seen that when the reaction time is 15 min, the ΔF of the system is the largest, so the reaction time of 15 min is selected for the following experiments.

[0066] Effect of reaction temperature:

[0067] Set up a control group and a test group, add 4mL of carbon quantum dot solution and 1.5mL of potassium permanganate standard solution to two 10mL stoppered colorimetric tubes in sequence, add 2mL of isoniazid standard solution to one colorimetric tube as the test group, and the other as the control group, and dilute to 10mL and shake well. The above solutions were placed in 30℃, 40℃, 50℃, 60℃, and 70℃ for 15min, and the maximum fluorescence intensity F1 of the control group solution and the maximum fluorescence intensity F2 of the test group solution were measured respectively. The difference ΔF=F2-F1 was calculated, and the correlation curve between temperature change and ΔF was made, as shown in the figure. Figure 6 shown.

[0068] Figure 6 This is the effect of temperature on ΔF as described in Example 2. Figure 6 It can be seen that the ΔF value measured at 30°C is the largest, so the reaction temperature of 30°C was selected for the following experiments.

[0069] Example 3

[0070] Based on the experimental results of Example 1 and Example 2, this embodiment provides a method for determining the content of isoniazid using carbon quantum dots, and the specific steps are as follows:

[0071] (1) Preparation of standard curve: Prepare several clean 10mL stoppered colorimetric tubes and affix labels on them for identification. Then, add 4mL of carbon quantum dot solution and 1.5mL of potassium permanganate standard solution to one of the stoppered colorimetric tubes in sequence, which serves as control group T3. In addition to adding the same reagents as the control group, add 2mL of 0.25×10 -3 ~2×10 -3 mol / L series concentration of isoniazid standard solution, as the test group T4, all colorimetric tubes are fixed to 10mL, shaken, and reacted at 30℃ for 15min, the reaction pH = 7. Start the fluorescence spectrophotometer, set the excitation wavelength to 397nm, and measure the fluorescence intensity F of the control solution. T3 And the fluorescence intensity F of the tested solution T4 , record the measurement results, and calculate ΔF=F T4 -F T3 Calculations were performed and finally a standard curve was produced, wherein the horizontal axis was the different concentrations of isoniazid and the vertical axis was ΔF. Figure 7 shown.

[0072] (2) Sample determination:

[0073] 1) Grind 6 isoniazid tablets in a mortar and pestle until evenly distributed. Prepare a dry beaker and accurately weigh an appropriate amount of fine powder (equivalent to 0.0137g isoniazid). Add this to the beaker and then add an appropriate volume of distilled water to dissolve it. Place the dissolved isoniazid sample in an ultrasonic instrument to fully dissolve it, then transfer it to a 100mL volumetric flask. Drain with a glass rod and wash with distilled water several times. Finally, bring to a constant volume to obtain an isoniazid sample solution for later use.

[0074] 2) Take two clean 10mL stoppered colorimetric tubes. For the first colorimetric tube, add 4mL of carbon quantum dot solution and 1.5mL of potassium permanganate standard solution in sequence as the control group. For the second colorimetric tube, in addition to adding 4mL of carbon quantum dot solution and 1.5mL of potassium permanganate standard solution, add 2mL of the above-mentioned isoniazid sample solution to be used as the test group. Then, make up the volume and shake well, and react at 30℃ for 15min, and the reaction pH = 7. Finally, measure the fluorescence intensity of the control solution and the test solution at an excitation wavelength of 397nm, which are F and F, respectively. T1 and F T2 , then calculate ΔF=F T2 -F T1 The isoniazid sample solution of the same concentration was measured six times in parallel under the same conditions, and the measurement results were recorded. The results are shown in Table 3.

[0075] Table 3 Determination of the content of isoniazid tablets (n=6)

[0076]

[0077]

[0078] Finally, the actual isoniazid content in isoniazid tablets was determined, and the actual isoniazid content was 0.1g / tablet. After six parallel experiments, there was basically no significant difference in the experimental phenomena and experimental results of the six measurements in the test group and the control group. After data processing and calculation, it was found that the concentration of isoniazid tablets determined by this method was 1.03×10 -3 mol / L, which is converted to an isoniazid content of 0.097 g / tablet in isoniazid tablets, which is close to the drug specification, and the RSD value is 1.7%. This proves that the method of the present invention is simple, rapid, and accurate.

[0079] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0080] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. Application of carbon quantum dots in the determination of isoniazid content in isoniazid tablets.

2. Application of carbon quantum dots in fluorescence detection of isoniazid content in isoniazid tablets.

3. A method for determining the content of isoniazid using carbon quantum dots, characterized in that: The steps include: Preparation of standard curve: The mixed solution of carbon quantum dot solution and potassium permanganate standard solution was used as the control group T3, and the mixed solution of isoniazid standard solution, carbon quantum dot solution and potassium permanganate standard solution with a series of concentrations was used as the test group T4. The fluorescence intensity F T3 And the fluorescence intensity F of the test group T4 T4 , then calculate ΔF=F T4 -F T3 , then make a standard curve with isoniazid concentration as the horizontal axis and ΔF as the vertical axis; Determination of isoniazid content: a mixed solution of carbon quantum dot solution and potassium permanganate standard solution was used as the control group T1, and a mixed solution of isoniazid sample solution, carbon quantum dot solution and potassium permanganate standard solution was used as the test group T2. The fluorescence intensity F of the control group T1 was measured respectively. T1 And the fluorescence intensity F of the test group T2 T2 , then calculate ΔF=F T2 -F T1 ; Substitute ΔF into the standard curve to calculate the isoniazid concentration.

4. The method according to claim 3, characterized in that The concentration of isoniazid in the isoniazid standard solution of the series of concentrations is 0.25×10 -3 ~2×10 -3 mol / L; the standard curve is y=285.55x+239.25, R 2 =0.9959, the detection limit is 2.6×10 -5 mol / L.

5. The method according to claim 3, characterized in that The volume ratio of the carbon quantum dot solution and the potassium permanganate standard solution in the control group T3 was 4:1.5; the volume ratio of the isoniazid standard solution of the series of concentrations, the carbon quantum dot solution and the potassium permanganate standard solution in the test group T4 was 2:4:1.

5.

6. The method according to claim 3, characterized in that The volume ratio of the carbon quantum dot solution and the potassium permanganate standard solution in the control group T1 is 4:1.5; the volume ratio of the isoniazid sample solution to be tested, the carbon quantum dot solution and the potassium permanganate standard solution in the test group T2 is 2:4:1.

5.

7. The method according to claim 3, characterized in that The conditions for measuring fluorescence intensity were as follows: wavelength was 397 nm; each mixed solution was reacted at pH 7 and temperature 30° C. for 15 min before measuring fluorescence intensity.

8. The method according to claim 3, characterized in that The preparation steps of the carbon quantum dot solution include: mixing starch, ethylenediamine and water and then heat-treating to obtain a dark brown solution, filtering, fixing the filtrate to 100 mL, and diluting 50 times before use; The usage ratio of the starch, ethylenediamine and water is 8g:3mL:10mL.

9. The method according to claim 3, characterized in that The preparation step of the isoniazid sample solution to be tested comprises: dissolving the isoniazid sample to be tested in water, and fixing the volume to 100 mL to obtain the isoniazid sample solution to be tested.

10. The method according to claim 3, characterized in that The concentration of the potassium permanganate standard solution is 1×10 - 3 mol / L.

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