Method for detecting methamphetamine based on Co-AD quantum dot molecular imprinting fluorescence sensor

Abstract

The invention discloses a method for detecting methamphetamine based on a Co-AD quantum dot molecular imprinting fluorescence sensor. The method comprises the following steps: step 1, preparing Co-AD quantum dots; step 2, synthesizing a Co-AD quantum dot molecularly imprinted fluorescence sensor; 3, drawing a standard working curve of fluorescence quenching intensity-methamphetamine concentration; 4, measuring the content of methamphetamine in the sample; the Co-AD quantum dot molecularly imprinted fluorescent sensor prepared by the method combines high selectivity, simplicity, convenience and rapidness of molecularly imprinted polymer and high sensitivity of fluorescence detection, can accurately and specifically recognize methamphetamine, and is effectively applied to field rapid detection of drugs, the linear detection range of the detection method to methamphetamine is 67-469nM, and the detection method has a wide application prospect. The detection limit is as low as 23nM.

Description

Technical Field

[0001] The present invention belongs to the technical field of analytical chemistry detection, and in particular relates to a method for detecting methamphetamine based on a Co-AD quantum dot molecular imprinting fluorescence sensor. Background Art

[0002] Methamphetamine (METH), the main ingredient in ice, is called "ice" because it resembles ice. Methamphetamine is a stimulant that stimulates the central nervous system and is highly addictive. Long-term use can cause severe brain damage, leading to violent behaviors such as mania, self-destruction, and suicide. Methamphetamine exerts far greater psychological control over its users than physical control, making it more harmful and deceptive than traditional drugs like heroin, and its withdrawal effects are poor. Methamphetamine has become the most widely abused drug in my country, seriously endangering public health and social security and stability. Drug detection technologies play a vital role in identifying drug users, monitoring their drug status, and providing treatment. Common methods for measuring methamphetamine include chromatography, mass spectrometry, spectroscopy, and immunochromatography. These methods require specialized personnel to process samples and large, expensive testing equipment, which falls short of the practical needs of frontline police officers in drug enforcement and investigation.

[0003] Quantum dots are a new type of fluorescent material first discovered in 2004. Compared to organic fluorescent materials, quantum dots offer advantages such as controllable emission wavelengths, making them easier to study; high luminescence efficiency, one-step excitation, and a variety of colors; strong fluorescence intensity, long-lasting resistance to photobleaching; and ease of functionalization and electronic properties. Due to their unique physicochemical structure, quantum dots have been widely used in fluorescent probes, cell imaging, and biomarkers. To improve the selectivity of quantum dot-based sensors, molecularly imprinted polymers have been introduced to synthesize quantum dot-based molecularly imprinted fluorescence sensors for selective analyte detection. This fluorescence sensor transforms the molecular recognition process between the molecular imprint and the analyte into optical signal detection of the quantum dots, enabling selective identification and detection of target molecules in complex compositions. This approach improves both the specific recognition of the analyte and the sensitivity of the detection process. The highly sensitive and selective technical solution provided by the present invention has not yet been reported. Summary of the Invention

[0004] The present invention provides a method for detecting methamphetamine based on a Co-AD quantum dot molecular imprinting fluorescence sensor. The method is simple to operate and can quickly, accurately and specifically identify and detect the methamphetamine content in a sample.

[0005] The method for detecting methamphetamine based on Co-AD quantum dot molecular imprinting fluorescence sensor of the present invention is as follows: (1) Preparation of Co-AD quantum dots 0.16-0.2 g of cobalt chloride, 30-40 mg of epinephrine, and 1.9-2.1 g of citric acid were weighed and dissolved in deionized water. 45-55 μL of ethylenediamine was then added and mixed by ultrasonication. The mixture was then reacted at 170-190°C in a microwave oven for 1-2 hours to prepare Co-AD quantum dots. (2) Preparation of Co-AD quantum dot molecularly imprinted fluorescence sensor Methamphetamine (ice), α-methylpropionic acid, and Co-AD quantum dots were dissolved in acetonitrile and stirred evenly. Polyethylene glycol dimethacrylate and azobisisobutyronitrile were then added in sequence. After ultrasonic mixing, the mixture was shaken under a nitrogen atmosphere for prepolymerization. After the reaction, the reaction product was placed in a 65-75°C oil bath and stirred for 24 hours. The mixture was then cooled to room temperature and filtered. The filter residue was repeatedly washed with a methanol-acetic acid solution and dried to obtain a Co-AD quantum dot molecularly imprinted fluorescence sensor. The mass volume ratio of methamphetamine to α-methylpropionic acid in mg: μL is (15-20): (30-40), and the mass volume ratio of methamphetamine to Co-AD quantum dots in mg: mL is (15-20): (0.8-1); the volume ratio of α-methylpropionic acid to polyethylene glycol dimethacrylate is (30-40): (380-420), and the volume mass ratio of α-methylpropionic acid to azobisisobutyronitrile in μL: mg is (30-40): (16-24); The methanol-acetic acid solution is prepared by methanol and acetic acid in a volume ratio of (8-9):1; (3) Drawing of standard working curve A Co-AD quantum dot molecularly imprinted fluorescence sensor was added to a standard methamphetamine (ice) solution, the pH was adjusted to 7, and the volume was constant to prepare a methamphetamine solution with a concentration range of 0-469 nmol / L. The solution was mixed and shaken at 25-35°C for 5 minutes. The fluorescence intensity F of the mixture was measured using a fluorescence spectrophotometer at an excitation wavelength of 280 nm and an emission wavelength of 310 nm. The fluorescence intensity ratio F0 / F was calculated, where F0 is the fluorescence intensity of the reaction system without methamphetamine. The linear relationship between the methamphetamine concentration and the fluorescence intensity ratio was determined, and a regression equation was obtained. The usage of the Co-AD quantum dot molecular imprinting fluorescence sensor is 10-15 mg.

[0006] (4) Sample measurement Add the Co-AD quantum dot molecular imprinted fluorescence sensor to the sample to be tested, adjust the pH to 7, fix the volume, mix well, shake at 25-35°C for 5 minutes, and then use a fluorescence spectrophotometer to detect the fluorescence intensity of the mixed sample at an excitation wavelength of 280 nm and an emission wavelength of 310 nm. Calculate the fluorescence intensity ratio and substitute the fluorescence intensity ratio into the regression equation in step (2) to obtain the methamphetamine content in the sample to be tested; The usage of the Co-AD quantum dot molecular imprinting fluorescence sensor is 10-15 mg.

[0007] The advantages of the present invention are: 1. The present invention utilizes cobalt chloride, epinephrine, citric acid, and ethylenediamine using a microwave method to prepare water-soluble cobalt- and nitrogen-doped quantum dots with excellent fluorescence properties. The prepared quantum dots have a fluorescence yield of up to 16% and exhibit a fluorescence quenching effect on methamphetamine at 310 nm. Using the Co-AD quantum dot molecularly imprinted polymer as a fluorescence sensor, it can rapidly detect trace amounts of methamphetamine in suspicious samples. The method has high sensitivity, as other coexisting ions and analogs do not have this effect, and the method has good specificity. The linear detection range of the detection method of the present invention for methamphetamine is 67-469nM, the linear correlation coefficient is 0.9926, and the detection limit is as low as 23nM; 2. The method of detecting methamphetamine based on Co-AD quantum dot molecular imprinting fluorescence sensor of the present invention can be used for rapid detection of morphine in artificial urine. The method is simple, highly sensitive and specific. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 Fluorescence scanning diagram of the interaction between methamphetamine solutions of different concentrations and Co-AD quantum dot molecular imprinted fluorescence sensor; Figure 2 Fluorescence scanning diagram of the interaction between methamphetamine solutions of different concentrations and Co-AD quantum dot non-molecularly imprinted fluorescence sensor; Figure 3 This is a linear relationship diagram of the Co-AD quantum dot molecular imprinted fluorescence sensor (Co-AD QDs-MIPs) and the quantum dot non-imprinted fluorescence sensor (Co-AD QDs-NIPs) to methamphetamine in Example 1; Figure 4 The results show the effects of various coexisting ions on Co-AD quantum dot molecular imprinted fluorescence sensor; Figure 5 The results show the effects of common drugs on Co-AD quantum dot molecular imprinting fluorescence sensors. DETAILED DESCRIPTION

[0009] The technical solution of the present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto; the reagents in the embodiments are conventional reagents unless otherwise specified, and the methods are conventional methods unless otherwise specified; Example 1: Determination of methamphetamine content in artificial urine. The specific operating steps are as follows: (1) 0.16 g of cobalt chloride, 30 mg of epinephrine, and 2.1 g of citric acid were weighed and dissolved in 30 mL of deionized water. 50 μL of ethylenediamine was then added, ultrasonicated for 30 minutes, and microwave-heated in a microwave digester at 180 °C for 1 hour to obtain Co-AD quantum dots (Co-AD QDs). 15 mg of methamphetamine, 35 μL of α-methylpropionic acid, and 1 mL of Co-AD quantum dots were dissolved in 4 mL of acetonitrile and stirred evenly. 380 μL of polyethylene glycol dimethacrylate and 16 mg of azobisisobutyronitrile were then added in sequence. The mixture was ultrasonicated for 10 minutes, nitrogen was introduced, sealed, and shaken for 30 minutes for prepolymerization. After prepolymerization, the reaction product was placed in a 70°C oil bath and stirred for 24 hours. The mixture was then cooled to room temperature and filtered. The solid was repeatedly washed with methanol-acetic acid solution (volume ratio 9:1) to remove methamphetamine and residual reagents in the polymer. Finally, the product was dried to obtain a white powder, which is the Co-AD quantum dot molecularly imprinted fluorescent sensor (Co-AD QDs-MIPs). At the same time, a non-molecularly imprinted fluorescent sensor (Co-AD QDs-NIPs) was prepared according to the above method, except that methamphetamine was not added during the preparation process; (2) Drawing of standard working curve A methamphetamine standard solution was prepared using deionized water. 10 mg of Co-AD quantum dot molecularly imprinted fluorescence sensor was added to the methamphetamine standard solution, the pH was adjusted to 7, and the volume was diluted to 4 mL with water to obtain methamphetamine standard solutions with concentrations of 0, 67, 134, 201, 268, 335, 402, and 469 nmol / L. The solution was mixed and shaken at 30°C for 5 minutes. The fluorescence intensity of the mixture was measured using a fluorescence spectrophotometer at an excitation wavelength of 280 nm and an emission wavelength of 310 nm, respectively ( Figure 1 and Figure 3 ); The same method was used to determine the fluorescence intensity of methamphetamine solutions with different concentrations and Co-AD quantum dot molecular imprinted fluorescence sensors (Co-AD QDs-MIPs). Figure 2 and Figure 3 ).

[0010] Depend on Figure 1 and Figure 2It can be seen that with the increase of methamphetamine concentration, the fluorescence intensity of Co-AD quantum dot molecular imprinting fluorescence sensor and non-molecular imprinting fluorescence sensor at 310nm gradually weakened, and the quenching efficiency of molecular imprinting fluorescence sensor was stronger than that of non-molecular imprinting fluorescence sensor.

[0011] With methamphetamine concentration as the horizontal axis and fluorescence intensity ratio (F0 / F) as the vertical axis (F0 is the fluorescence intensity of the reaction system when the methamphetamine concentration is 0 nM), a standard working curve was drawn to obtain the linear regression equation F 310nm =0.00066C+0.977, correlation coefficient R 2 =0.9926 (see Figure 3 ); (3) Prepare artificial urine according to the method described in “Voltammetric study and determination of the new psychoactive substances 25H-NBOH and 25B-NBOH in synthetic urine and blotter paper samplesusing a composite electrode(Electrochim Acta, 484: 114051)”; weigh 0.110 g CaCl2·2H2O, 0.293 g NaCl, 0.225 g Na2SO4, 0.140 g KH2PO4, 0.106 g KCl, 0.1 g NH4Cl, and 2.5 g urea into water, sonicate for 10 min, adjust the pH to 7.0 with 2.0 mol / L NaOH solution, dilute to 100 mL, and refrigerate for later use; (4) Take 4 mL of the artificial urine prepared in step (3), add methamphetamine to a concentration of 88 nM, then add 10 mg of the Co-AD quantum dot molecular imprinted fluorescence sensor, mix well, and shake at 30°C for 5 minutes. Use a fluorescence spectrophotometer to measure the fluorescence intensity of the artificial urine sample at an excitation wavelength of 280 nm and an emission wavelength of 310 nm, calculate the fluorescence intensity ratio, substitute the fluorescence intensity ratio into the linear regression equation in step (2), and calculate the methamphetamine content in the artificial urine to be 87 nM; (5) Specific detection of fluorescent sensors According to step (4), artificial urine was used to prepare a solution containing methamphetamine and coexisting ions (Al 3+ Br - , Ca 2+ 、Cl - 、Cu 2+ 、Fe 3+ , K + Mg 2+ 、Na+ 、Zn 2+ 、NO3 - and PO4 3- ) (the concentrations of methamphetamine and coexisting ions were both 201 nM), or the methamphetamine in the above reaction system was replaced with common drugs (heroin, caffeine, cocaine, morphine and ephedrine) (the concentrations were all 201 nM), and then the Co-AD quantum dot molecular imprinted fluorescence sensor was added to detect the specificity of the reaction system of the present invention. The results are shown in FIG. Figure 4 、 Figure 5 ,From the figure, we can see that various coexisting ions and common drugs have no ,interference on the determination of methamphetamine, and the method has good ,specificity; (6) Recovery and precision experiments Three different concentrations of methamphetamine standard solutions were added to artificial urine, and each concentration was measured three times in parallel. The spiked recovery rate and relative standard deviation (RSD) were calculated. The results are shown in Table 1. The spiked recovery rate of morphine was measured to be between 95.8% and 97.4%, and the RSD was between 1.89% and 2.54%. This method has good accuracy and precision. Table 1 Recovery rate test data .

[0012] Example 2: Determination of methamphetamine content in artificial urine. The specific steps are as follows: (1) Weigh 0.2 g of cobalt chloride, 40 mg of epinephrine, and 1.9 g of citric acid, respectively, and dissolve them in 30 mL of deionized water. Then, add 50 μL of ethylenediamine, sonicate for 30 minutes, and heat in a microwave digester at 180 °C for 1 hour to obtain Co-AD quantum dots. 20 mg of methamphetamine, 40 μL of α-methylpropionic acid, and 0.8 mL of Co-AD quantum dots were dissolved in 4 mL of acetonitrile and stirred evenly. 400 μL of polyethylene glycol dimethacrylate and 24 mg of azobisisobutyronitrile were added in sequence. The mixture was ultrasonicated for 10 minutes, nitrogen was introduced, sealed, and shaken for 30 minutes for prepolymerization. After prepolymerization, the solution was placed in a 70°C oil bath and stirred for 24 hours. It was then cooled to room temperature and filtered. The solid was then repeatedly washed with methanol-acetic acid solution (volume ratio 8:1) and finally dried. The white powder product was the Co-AD quantum dot molecularly imprinted fluorescent sensor. (2) Drawing of the standard working curve: same as step (2) in Example 1; (3) Preparation of artificial urine: same as step (3) in Example 1; (4) Take 4 mL of the artificial urine prepared in step (3), add methamphetamine to a concentration of 110 nM, add 10 mg of the Co-AD quantum dot molecular imprinted fluorescence sensor, mix well, and shake at 30°C for 5 minutes. Use a fluorescence spectrophotometer to measure the fluorescence intensity of the artificial urine sample at an excitation wavelength of 280 nm and an emission wavelength of 310 nm. Calculate the fluorescence intensity ratio, substitute the fluorescence intensity ratio into the linear regression equation in step (2), and calculate the methamphetamine content in the artificial urine to be 115 nM. According to the recommendation of the International Union of Pure and Applied Chemistry (IUPAC), the detection limit is calculated to be 23 nM at 3 s / k (s is the standard deviation of 10 consecutive blank solutions, and k is the slope of the linear regression equation).

[0013] Example 3: Determination of methamphetamine content in artificial urine. The specific steps are as follows: (1) Weigh 0.16 g of cobalt chloride, 30 mg of epinephrine, and 2.0 g of citric acid, respectively, and dissolve them in 30 mL of deionized water. Then, add 50 μL of ethylenediamine, sonicate for 30 minutes, and heat in a microwave digester at 180 °C for 1 hour to obtain Co-AD quantum dots. 15 mg of methamphetamine, 35 μL of α-methylpropionic acid, and 0.9 mL of Co-AD quantum dots were dissolved in 4 mL of acetonitrile and stirred evenly. 420 μL of polyethylene glycol dimethacrylate and 20 mg of azobisisobutyronitrile were added in sequence. The mixture was ultrasonicated for 10 minutes, nitrogen was introduced, sealed, and shaken for 30 minutes for prepolymerization. After prepolymerization, the solution was placed in a 70°C oil bath and stirred for 24 hours. It was then cooled to room temperature and filtered. The solid was then repeatedly washed with methanol / acetic acid solution (volume ratio 9:1) and finally dried. The white powder product was the Co-AD quantum dot molecularly imprinted fluorescent sensor. (2) Drawing of the standard working curve: same as step (2) in Example 1; (3) Preparation of artificial urine: same as step (4) in Example 1; (4) Sample determination: Take 4 mL of the artificial urine prepared in step 4, add methamphetamine to a concentration of 350 nM, add 10 mg of the Co-AD quantum dot molecular imprinted fluorescence sensor, mix well, and shake at 30°C for 5 minutes. Use a fluorescence spectrophotometer to measure the fluorescence intensity of the artificial urine sample at an excitation wavelength of 280 nm and an emission wavelength of 310 nm. Calculate the fluorescence intensity ratio and substitute the fluorescence intensity ratio into the linear regression equation in step (2). The methamphetamine content in the artificial urine is calculated to be 352 nM, with a relative standard deviation of 2.12%.

Claims

1. A method for detecting methamphetamine based on Co-AD quantum dot molecular imprinting fluorescence sensor, characterized in that: Here are the steps: (1) Weigh 0.16-0.2 g of cobalt chloride, 30-40 mg of epinephrine, and 1.9-2.1 g of citric acid, respectively, and dissolve them in deionized water. Then, add 45-55 μL of ethylenediamine, mix them by ultrasonication, and react them at 170-190 °C under microwave conditions for 1-2 hours to prepare Co-AD quantum dots. Methamphetamine, α-methylpropionic acid, and Co-AD quantum dots were dissolved in acetonitrile and stirred evenly, and polyethylene glycol dimethacrylate and azobisisobutyronitrile were added in sequence. After ultrasonic mixing, the mixture was shaken under a nitrogen atmosphere for prepolymerization. After the reaction, the reaction product was placed in a 65-75°C oil bath and stirred for 24 hours, then cooled to room temperature and filtered. The filter residue was repeatedly washed with a methanol-acetic acid solution and dried to obtain a Co-AD quantum dot molecularly imprinted fluorescence sensor. (2) Add Co-AD quantum dot molecular imprinted fluorescence sensor to the methamphetamine standard solution, adjust the pH to 7, and constant volume to prepare a methamphetamine solution with a concentration range of 0-469 nmol / L. Mix well, shake at 25-35°C for 5 minutes, and use a fluorescence spectrophotometer to measure the fluorescence intensity F of the mixture at an excitation wavelength of 280 nm and an emission wavelength of 310 nm. Calculate the fluorescence intensity ratio F0 / F, where F0 is the fluorescence intensity of the reaction system without adding methamphetamine. Determine the linear relationship between the methamphetamine concentration and the fluorescence intensity ratio, and obtain the regression equation; (3) Add the Co-AD quantum dot molecular imprinted fluorescence sensor to the sample to be tested, adjust the pH to 7, fix the volume, mix well, shake at 25-35°C for 5 minutes, and then use a fluorescence spectrophotometer to detect the fluorescence intensity of the mixed sample at an excitation wavelength of 280 nm and an emission wavelength of 310 nm. Calculate the fluorescence intensity ratio and substitute the fluorescence intensity ratio into the regression equation in step (2) to obtain the methamphetamine content in the sample to be tested.

2. The method for detecting methamphetamine using a Co-AD quantum dot molecularly imprinted fluorescence sensor according to claim 1, wherein: The mass volume ratio of methamphetamine to α-methylpropional is (15-20): (30-40) in mg: μL, and the mass volume ratio of methamphetamine to Co-AD quantum dots is (15-20): (0.8-1) in mg: mL.

3. The method for detecting methamphetamine using a Co-AD quantum dot molecularly imprinted fluorescence sensor according to claim 1, wherein: The volume ratio of α-methylpropionic acid to polyethylene glycol dimethacrylate is (30-40):(380-420), and the volume mass ratio of α-methylpropionic acid to azobisisobutyronitrile in μL:mg is (30-40):(16-24).

4. The method for detecting methamphetamine using a Co-AD quantum dot molecularly imprinted fluorescence sensor according to claim 1, wherein: The methanol-acetic acid solution is prepared by mixing methanol and acetic acid in a volume ratio of (8-9):

1.

5. The method for detecting methamphetamine using a Co-AD quantum dot molecularly imprinted fluorescence sensor according to claim 1, wherein: The added amount of Co-AD quantum dot molecular imprinting fluorescence sensor is 10-15 mg.

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