CN113804744B - Quick morphine detection method based on carboxylated multiwall carbon nanotube modified electrode - Google Patents
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- BQJCRHHNABKAKU-KBQPJGBKSA-N morphine Chemical compound O([C@H]1[C@H](C=C[C@H]23)O)C4=C5[C@@]12CCN(C)[C@@H]3CC5=CC=C4O BQJCRHHNABKAKU-KBQPJGBKSA-N 0.000 title claims abstract description 154
- 229960005181 morphine Drugs 0.000 title claims abstract description 77
- 238000001514 detection method Methods 0.000 title claims abstract description 42
- 239000002048 multi walled nanotube Substances 0.000 title claims abstract description 21
- 229910021397 glassy carbon Inorganic materials 0.000 claims abstract description 17
- 238000001179 sorption measurement Methods 0.000 claims abstract description 13
- 238000003950 stripping voltammetry Methods 0.000 claims abstract description 11
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 25
- 239000002041 carbon nanotube Substances 0.000 claims description 24
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 24
- 238000000034 method Methods 0.000 claims description 21
- 230000004044 response Effects 0.000 claims description 21
- 239000000243 solution Substances 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
- 239000008367 deionised water Substances 0.000 claims description 12
- 229910021641 deionized water Inorganic materials 0.000 claims description 12
- 238000001903 differential pulse voltammetry Methods 0.000 claims description 12
- 239000007853 buffer solution Substances 0.000 claims description 11
- 239000007788 liquid Substances 0.000 claims description 11
- 230000003647 oxidation Effects 0.000 claims description 10
- 238000007254 oxidation reaction Methods 0.000 claims description 10
- 238000005516 engineering process Methods 0.000 claims description 9
- 238000006243 chemical reaction Methods 0.000 claims description 7
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 6
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 5
- 239000006185 dispersion Substances 0.000 claims description 5
- 229910017604 nitric acid Inorganic materials 0.000 claims description 5
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- 238000005406 washing Methods 0.000 claims description 4
- 238000005303 weighing Methods 0.000 claims description 4
- 102100025912 Melanopsin Human genes 0.000 claims description 3
- 229910021607 Silver chloride Inorganic materials 0.000 claims description 3
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 3
- 238000000970 chrono-amperometry Methods 0.000 claims description 3
- 238000001035 drying Methods 0.000 claims description 3
- 238000012417 linear regression Methods 0.000 claims description 3
- 239000013213 metal-organic polyhedra Substances 0.000 claims description 3
- 238000012011 method of payment Methods 0.000 claims description 3
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 claims description 3
- 239000003115 supporting electrolyte Substances 0.000 claims description 3
- 238000009210 therapy by ultrasound Methods 0.000 claims description 3
- 238000012512 characterization method Methods 0.000 claims description 2
- 238000002484 cyclic voltammetry Methods 0.000 claims description 2
- 239000002270 dispersing agent Substances 0.000 claims description 2
- 230000033116 oxidation-reduction process Effects 0.000 claims description 2
- 229910052799 carbon Inorganic materials 0.000 claims 1
- 238000003756 stirring Methods 0.000 claims 1
- 230000035945 sensitivity Effects 0.000 abstract description 6
- 238000004458 analytical method Methods 0.000 abstract description 5
- 230000010354 integration Effects 0.000 abstract description 3
- 238000012423 maintenance Methods 0.000 abstract description 3
- 230000021523 carboxylation Effects 0.000 abstract description 2
- 238000006473 carboxylation reaction Methods 0.000 abstract description 2
- 238000004451 qualitative analysis Methods 0.000 abstract 1
- 238000004445 quantitative analysis Methods 0.000 abstract 1
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 28
- 229940079593 drug Drugs 0.000 description 13
- 239000003814 drug Substances 0.000 description 13
- 238000012986 modification Methods 0.000 description 8
- 230000004048 modification Effects 0.000 description 8
- 239000002574 poison Substances 0.000 description 8
- 231100000614 poison Toxicity 0.000 description 8
- 239000000523 sample Substances 0.000 description 8
- 239000000463 material Substances 0.000 description 6
- 238000002360 preparation method Methods 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- OROGSEYTTFOCAN-DNJOTXNNSA-N codeine Chemical compound C([C@H]1[C@H](N(CC[C@@]112)C)C3)=C[C@H](O)[C@@H]1OC1=C2C3=CC=C1OC OROGSEYTTFOCAN-DNJOTXNNSA-N 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 241001481789 Rupicapra Species 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 239000010985 leather Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000005498 polishing Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- GVGLGOZIDCSQPN-PVHGPHFFSA-N Heroin Chemical compound O([C@H]1[C@H](C=C[C@H]23)OC(C)=O)C4=C5[C@@]12CCN(C)[C@@H]3CC5=CC=C4OC(C)=O GVGLGOZIDCSQPN-PVHGPHFFSA-N 0.000 description 2
- YNAVUWVOSKDBBP-UHFFFAOYSA-N Morpholine Chemical compound C1COCCN1 YNAVUWVOSKDBBP-UHFFFAOYSA-N 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 239000012472 biological sample Substances 0.000 description 2
- 229960004126 codeine Drugs 0.000 description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- OROGSEYTTFOCAN-UHFFFAOYSA-N hydrocodone Natural products C1C(N(CCC234)C)C2C=CC(O)C3OC2=C4C1=CC=C2OC OROGSEYTTFOCAN-UHFFFAOYSA-N 0.000 description 2
- 238000001727 in vivo Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 230000004060 metabolic process Effects 0.000 description 2
- 238000005457 optimization Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- USSIQXCVUWKGNF-UHFFFAOYSA-N 6-(dimethylamino)-4,4-diphenylheptan-3-one Chemical compound C=1C=CC=CC=1C(CC(C)N(C)C)(C(=O)CC)C1=CC=CC=C1 USSIQXCVUWKGNF-UHFFFAOYSA-N 0.000 description 1
- XADCESSVHJOZHK-UHFFFAOYSA-N Meperidine Chemical compound C=1C=CC=CC=1C1(C(=O)OCC)CCN(C)CC1 XADCESSVHJOZHK-UHFFFAOYSA-N 0.000 description 1
- 239000008896 Opium Substances 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000004082 amperometric method Methods 0.000 description 1
- 230000003444 anaesthetic effect Effects 0.000 description 1
- 239000000872 buffer Substances 0.000 description 1
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- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000004587 chromatography analysis Methods 0.000 description 1
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- 238000012790 confirmation Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 229960002069 diamorphine Drugs 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002290 gas chromatography-mass spectrometry Methods 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 238000003018 immunoassay Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000004949 mass spectrometry Methods 0.000 description 1
- 230000004630 mental health Effects 0.000 description 1
- 229960001797 methadone Drugs 0.000 description 1
- 239000003607 modifier Substances 0.000 description 1
- 239000004081 narcotic agent Substances 0.000 description 1
- 229940124636 opioid drug Drugs 0.000 description 1
- 229960001027 opium Drugs 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000007517 polishing process Methods 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- BUCIWTBCUUHRHZ-UHFFFAOYSA-K potassium;disodium;dihydrogen phosphate;hydrogen phosphate Chemical compound [Na+].[Na+].[K+].OP(O)([O-])=O.OP([O-])([O-])=O BUCIWTBCUUHRHZ-UHFFFAOYSA-K 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000008439 repair process Effects 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/416—Systems
- G01N27/48—Systems using polarography, i.e. measuring changes in current under a slowly-varying voltage
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/308—Electrodes, e.g. test electrodes; Half-cells at least partially made of carbon
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- Health & Medical Sciences (AREA)
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- Chemical Kinetics & Catalysis (AREA)
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- Molecular Biology (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Carbon And Carbon Compounds (AREA)
Abstract
The invention relates to a rapid morphine detection method based on carboxylation multiwall carbon nanotube modified electrodes, which comprises the steps of carboxylating multiwall carbon nanotubes, modifying the multiwall carbon nanotubes on the polished and characterized glassy carbon electrode surface by adopting a dripping mode, and realizing rapid qualitative and quantitative analysis of morphine by adopting a differential pulse adsorption stripping voltammetry. The detection method optimizes the detection conditions, has the characteristics of simple instrument operation, low cost, no need of complex instrument maintenance, higher sensitivity, higher analysis speed and more miniaturization and integration.
Description
Technical Field
The invention relates to a rapid detection method of drugs, in particular to a rapid detection method of morphine based on carboxylated multiwall carbon nanotube modified electrodes.
Background
Opium drugs are drugs with longest use history, widest popular range and most serious harm in the world, and morphine drugs mainly comprise natural drugs such as morphine, codeine and the like, semisynthetic drugs such as heroin and the like, and artificially synthesized tube products such as dolantin, methadone and the like. Morphine (MOP) is an important component of opioid drugs, the final metabolite of heroin, morphine and codeine, and is also a clinically common narcotic drug. As an opioid, it can cause serious harm to the physical and mental health of the social stability and drug-taking personnel; as a clinical anesthetic, it has a positive effect of relieving pain of patients. The analysis of drugs is an important component of forensic science, so that a method capable of simply and sensitively detecting the morphine content in a biological sample is established, whether a test object takes poison, the poison taking degree and the poison taking history, the relationship between poison taking and death and the like are determined, a research basis is provided for metabolism of abused drugs in vivo, timely and accurate scientific evidence can be provided for case detection and treatment related to drugs, and the method is significant in the detection of forbidden cases.
The conventional methods for detecting MOP include chromatography, spectroscopy, immunoassay, mass spectrometry and electrochemical sensor methods or a combination of several technologies, and these conventional detection means can accurately detect the content of the morpholine, however, these detection methods require large instruments and are operated by professionals, or they have insufficient anti-interference capability and specificity, require complex sample pretreatment processes, and are difficult to meet the requirements of on-site rapid detection. The traditional rapid on-site drug detection method mainly adopts a test paper method (immune colloidal gold technology), and the method has the advantages of rapid detection, convenient operation, but also has the defects of low specificity, low sensitivity and the like. Therefore, it is also necessary to carry out confirmation analysis by using a precise instrument such as GC-MS.
Disclosure of Invention
The invention aims to provide a rapid morphine detection method based on carboxylated multiwall carbon nanotube modified electrodes. The carboxylated carbon nano tube is used as a modification material, and the adsorption stripping voltammetry is used as a detection technology, so that the response signal of Morphine (MOP) on the sensor can be effectively improved, and the rapid and high-sensitivity detection of MOP is finally realized. The method has the advantages of simple instrument operation, low price, no need of complex instrument maintenance, higher sensitivity, faster analysis speed and more miniaturization and integration.
In order to achieve the above purpose, the present invention provides the following technical solutions:
a morphine rapid detection method based on carboxylated carbon nanotube modified electrode comprises the following steps:
step one: carboxylation of multiwall carbon nanotubes (MWNTs) with concentrated nitric acid to obtain carboxylated carbon nanotubes (MWNTs-COOH), and preparing deionized water as dispersant to 1mg mL -1 Is a dispersion of (a);
step two: modifying MWNTs-COOH dispersion liquid on the polished and characterized Glassy Carbon Electrode (GCE) surface by using a pipetting gun in a direct dripping mode to obtain a carboxylated carbon nanotube modified glassy carbon electrode (MWNTs-COOH/GCE);
step three: the MOP with unknown concentration is detected by adopting a Differential Pulse Adsorption Stripping Voltammetry (DPASV), and the specific operation is as follows: firstly enriching under a certain potential to enable MOP to be pre-enriched on the surface of an electrode, then detecting by adopting a Differential Pulse Voltammetry (DPV), and obtaining the concentration of MOP in an unknown solution according to the relation between oxidation peak current and morphine concentration.
The rapid morphine detection method based on carboxylated carbon nanotube modified electrode comprises the following steps of:
(1) Preparation of MWNTs-COOH: 50mg of MWNTs were weighed into a 250mL round bottom flask, 100mL of concentrated nitric acid was added, and the reaction was stirred in an oil bath at 90℃for 4 hours. Washing with deionized water to neutrality after the reaction is finished, and drying in an oven for standby;
(2) Preparing a modification liquid: accurately weighing 1mg of the MWNTs-COOH obtained by the preparation method in a 1.5mL centrifuge tube, adding 1mL of deionized water, and performing ultrasonic treatment for 2 hours to uniformly disperse the MWNTs-COOH to obtain 1mg mL -1 Is a modified liquid of (a);
(3) Preparation of MWNTs-COOH/GCE: by using a three-electrode system, al is passed through 2 O 3 The polished GCE is used as a working electrode and is placed at a concentration of 5mmol L -1 K 3 [Fe(CN) 6 ]And 0.1mol L -1 Characterization in KCl solution by cyclic voltammetry, when Fe (CN) 6 3-/4- The electrode can be used continuously when the oxidation-reduction peak difference is less than 100 mV; after the GCE surface is dried, taking 4 mu L of MWNTs-COOH which are uniform by ultrasonic through a liquid transferring gun, directly dripping the MWNTs-COOH on the treated GCE surface, placing the GCE surface under an infrared lamp for baking for about five minutes, and volatilizing water to obtain the MWNTs-COOH/GCE;
(4) Detection of MOP: the method comprises the steps of adopting a three-electrode system, adopting MWNTs-COOH/GCE as a working electrode, adopting Ag/AgCl as a reference electrode, adopting a Pt wire electrode as a counter electrode, adopting a phosphoric acid buffer solution with pH=7.0 as a supporting electrolyte, firstly adopting a chronoamperometry as an enrichment technology, enriching for 300s at a potential of-0.2V, and then adopting DPV as a detection technology to detect the oxidation peak current of MOP in the solution.
Electrochemical sensors (ECS) are a type of device that can acquire and process information, and can convert the chemical quantity of an object to be detected into a detectable electrochemical signal, and establish a certain relationship between the two variables, so as to achieve the purpose of detecting the chemical quantity of the object to be detected by detecting the electrochemical signal. The electrochemical instrument has the advantages of simple operation, low price, no need of complex instrument maintenance, higher sensitivity, higher analysis speed, more and more miniaturization and integration, and the like. Adsorption stripping voltammetry is the adsorption transfer of certain biomolecules, drugs or organic compounds from a solution to the electrode surface and the continuous enrichment on the electrode. Because the electrode area is small, the concentration of the measured substance on the surface of the electrode is far greater than that in the bulk solution. According to the invention, the carboxylated carbon nano tube is used as a modification material of the morphine electrochemical sensor, and MOP is enriched under a certain potential, so that the conductivity of the sensor can be greatly improved. The invention establishes a method capable of simply and sensitively detecting the morphine content in a biological sample, determines whether a test object takes poison, the poison taking degree and the poison taking history, the relationship between poison taking and death and the like, provides a research foundation for metabolism of abused drugs in vivo, can provide timely and accurate scientific evidence for case detection and treatment related to drugs, and has great significance in case detection forbidden. The carboxylated multiwall carbon nanotube is used as a repair material to greatly amplify an electrochemical response signal of morphine, and meanwhile, the adsorption stripping voltammetry is adopted for detection to pre-enrich MOP on the surface of an electrode, so that the detection sensitivity of MOP can be further reduced.
The sensor is simple to prepare and quick to detect, the detection material does not need complex sample pretreatment, and the response signal of MOP on the sensor can be effectively improved by taking the carboxylated carbon nano tube as a modification material and simultaneously taking an adsorption stripping voltammetry as a detection method.
Drawings
FIG. 1 shows 3.0X10-5 mol L at different enrichment potentials according to the invention -1 Peak current response of MOP on MWNTs-COOH/GCE (enrichment time: 300s, ph=7.0).
FIG. 2 shows 3.0X10-5 mol L at different enrichment times according to the invention -1 Peak current response of MOP on MWNTs-COOH/GCE (enrichmentPotential: -0.2v, ph=7.0).
FIG. 3 shows the pH of the buffer solution of the present invention against 3.0X10-5 mol L -1 Peak current response of MOP on MWNTs-COOH/GCE (enrichment time: 300s, enrichment potential = -0.2V).
FIG. 4 shows peak current responses of various concentrations of morphine on MWNTs-COOH/GCE (concentration of 1.0X10-7, 3.0X10-7, 5.0X10-7, 8.0X10-7, 1.0X10-6, 3.0X10-6, 5.0X10-6, 8.0X10-6, 1.0X10-5, 3.0X10-5, 5.0X10-5, 8.0X10-5, 1.0X10-4 mol L from bottom to top) -1 The method comprises the steps of carrying out a first treatment on the surface of the Enrichment potential: -0.2V, enrichment time: 300s, ph=7.0).
FIG. 5 is a standard operating curve of the present invention.
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be given with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Examples
The description herein refers to: MWNTs-COOH is carboxylated multi-wall carbon nano-tube; GCE is a glassy carbon electrode; MOP is morphine.
Preparation of MWNTs-COOH:
50mg of MWNTs were weighed into a 250mL round bottom flask, 100mL of concentrated nitric acid was added, and the reaction was stirred in an oil bath at 90℃for 4 hours. And after the reaction is finished, washing the mixture to be neutral by deionized water, and drying the mixture in an oven for standby.
Preparation of MWNTs-COOH/GCE:
the first step: GCE was polished with 0.3 μm Al first 2 O 3 And adding a proper amount of deionized water to polish the chamois leather, wherein an 8-shaped grinding method is used for avoiding uneven stress during polishing, a coin-sized circle is drawn on the chamois leather according to a splayed track, meanwhile, whether the contact surface of the glassy carbon electrode and the chamois leather is parallel or not is noted, excessive force and too fast circling are not suitable, and the polishing is carried out for about ten minutes. After thatUsing Al with a diameter of 0.05 μm 2 O 3 The particles were ground and polished in the same manner for about five minutes. And (3) polishing for a period of time, and then cleaning by ultrasonic in deionized water to remove impurities, dirt and residual aluminum powder on the surface of the electrode. After washing, the mixture contained 5mmol L -1 K 3 [Fe(CN) 6 ]And 0.1mol L -1 CV scanning is carried out in KCl solution, when K 3 [Fe(CN) 6 ]The electrode can be used continuously when the redox peak difference is less than 100mV, and the electrode repeats the polishing process if the redox peak difference is more than 100 mV.
And a second step of: preparing a modification liquid: accurately weighing 1mg of the prepared carboxylated carbon nanotube in a 1.5mL centrifuge tube, adding 1mL deionized water, and performing ultrasonic treatment for 2 hours to uniformly disperse the carboxylated carbon nanotube to obtain 1mg mL -1 Is a modified liquid of (a); after the surface of the treated GCE is dried, adopting a dripping method to modify: and (3) taking a proper amount of ultrasonic uniform MWNTs-COOH dispersion liquid by a pipetting gun, directly dripping the MWNTs-COOH dispersion liquid on the surface of the treated GCE, placing the GCE on an infrared lamp, baking the GCE for about five minutes, and adsorbing the carboxylated carbon nano tubes on the surface of the glassy carbon electrode after the moisture is volatilized to prepare the glassy carbon electrode modified by the carboxylated carbon nano tubes. And (3) dripping for multiple times when the carboxylated carbon nanotube aqueous solution is dripped, so as to ensure the coverage uniformity of the carboxylated carbon nanotube aqueous solution.
The detection method comprises the following steps: the method comprises the steps of adopting a three-electrode system, adopting MWNTs-COOH/GCE as a working electrode, adopting Ag/AgCl as a reference electrode, adopting a Pt wire electrode as a counter electrode, adopting a phosphoric acid buffer solution with pH=7.0 as a supporting electrolyte, firstly adopting a chronoamperometry as an enrichment technology, enriching for 300s at a potential of-0.2V, and then adopting DPV as a detection technology to detect the oxidation peak current of MOP in the solution. After each test, the working electrode was put into deionized water and stirred for 60s to remove MOP adsorbed on the electrode surface at the time of measurement.
MWNTs-COOH/GCE is put into PBS buffer solution containing MOP with a certain concentration, and after enrichment for a certain time under a certain potential by using a time-lapse amperometry, DPV is used for scanning from 0.2V to 0.7V, and the oxidation peak current is recorded. After each test, the working electrode was placed in deionized water for 60s to remove MOP adsorbed on the electrode surface during the measurement.
Modification effect of carboxylated carbon nanotubes: experiments have compared the blank GCE with MWNTs-COOH/GCE at the same concentration MOP (3.0X10) -5 mol L -1 ) In (a) an electrochemical response. The response currents are respectively 4.334 multiplied by 10 -7 A、1.342×10 - 5 A, can be seen at 3.0X10 -5 mol L -1 The response current was approximately 31 times that of the bare GCE. The carboxylated carbon nano tube can be used as a modification material of the morphine electrochemical sensor, so that the detection sensitivity of the morphine electrochemical sensor is improved.
Selection of the modified amount of MWNTs-COOH: too little MWNTs can not completely cover the surface of the GCE electrode, and too much MWNTs can easily fall off due to too thick modified film thickness or cause too strong background current so that the oxidation peak of MOP is affected. The proper amount of modifier not only can effectively improve the performance of the sensor and save the reagent, but also can ensure the stability of the modified electrode. In order to obtain a preferable amount of the solution, experiments were carried out by using 2. Mu.L, 3. Mu.L, 4. Mu.L, 5. Mu.L and 1mg mL of the solution -1 MWNTs-COOH on the surface of the glassy carbon electrode, 3.0X10 g was measured according to the above method -5 mol L -1 MOP of (a) to detect. It was found during the experiment that the electrode surface could not be completely covered when the dispensing amount was 2. Mu.L, and was thus discarded. When 3. Mu.L, 4. Mu.L, 5. Mu.L of MWNTs-COOH were modified, the reaction was performed under the same detection conditions for 3.0X10 -5 mol L -1 The response of MOP of (C) was 5.58. Mu.A, 9.324. Mu.A, 8.71. Mu.A, respectively. The morphine DPV response was best when the modification amount was 4. Mu.L, so that 4. Mu.L was selected as the dropping amount.
Optimization of enrichment time and enrichment potential: and the MOP is detected by adopting a differential pulse adsorption stripping voltammetry method, and the enrichment potential and the enrichment time have great influence on the response peak current. As shown in FIG. 1, there was a large increase in DPV peak current when the enrichment potential increased from-1.0V to-0.6V, no significant difference in current from-0.6V to-0.2V Shi Feng, and the DPV response began to drop significantly as the enrichment potential continued to increase from-0.2V, especially with positive potential enrichment. This is probably because the carboxylated carbon nanotubes on the surface of the glassy carbon electrode have more-COO at negative potential - The groups are exposed to the electrode surface, facilitating adsorption of MOP. In addition, to avoid some gold at too low a potentialBelongs to ion precipitation, and selects-0.2V as enrichment potential. In the process of increasing the enrichment time from 60s to 480s, as shown in fig. 2, the MOP oxidation peak current is continuously increased, but the increase is reduced after the enrichment time exceeds 300s, so 300s is selected as the optimal enrichment time in consideration of detection timeliness.
Optimization of buffer pH: the oxidation process of morphine is accompanied by H + The pH of the buffer solution has an influence on its oxidation peak current. Na having pH=5.8, 6.5, 7.0, 7.5, 8.0 is disposed 2 HPO 4 -KH 2 PO 4 Buffer solution, detection 3.0X10 -5 mol L -1 Peak current response of MOP. As a result, as shown in fig. 3, there was a higher response peak current when the buffer solution was weakly acidic to neutral and a highest peak current under neutral conditions, and the response peak current of morphine was drastically decreased when the buffer solution was slightly alkaline, so that disodium hydrogen phosphate-potassium dihydrogen phosphate solution having ph=7.0 was selected as the buffer solution.
Drawing a standard working curve: under the optimal detection condition, the response peak currents of MOPs with different concentrations are measured by using a differential pulse adsorption stripping voltammetry method, and a standard working curve of the MOPs is drawn. As shown in FIG. 4, the peak current of morphine on MWNTs-COOH/GCE increased with increasing morphine concentration. At morphine concentration of 1.0X10 -7 mol L -1 ～1.0×10 -4 mol L -1 In the range of (2), the logarithm of morphine concentration (lgC) and the logarithm of DPV peak current (lgI) are linearly related, and as shown in fig. 5, the linear regression equation is lgI (μa) =0.687×lgc (μmol L) -1 )-0.068(r 2 ＝0.992)。
Detection of morphine as an actual sample: sample morphine was directly formulated as 3.7mg mL -1 After preparing MWNTs-COOH/GCE sensor and detecting sample morphine under optimal detection conditions, adding 200 μl of buffer solution of actual sample at 10ml ph=7.0, and adopting differential pulse adsorption stripping voltammetry with peak current response of 1.58 μa. And (3) carrying out standard working curve, and calculating to obtain the morphine content of the sample of 0.94%. Under optimal detection conditions, morphine concentration was 1.0X10 -7 mol L -1 ～1.0×10 -4 mol L -1 Ranges of (2)In the interior, the logarithm of morphine concentration (lgC) and the logarithm of DPV peak current (lgI) are linearly related, and the linear regression equation is lgI (μA) =0.687×lgc (μmol L) -1 )-0.068(r 2 =0.992). The actual morphine sample was detected and calculated to give a mass fraction of 0.94%.
Claims (4)
1. A rapid morphine detection method based on carboxylated multiwall carbon nanotube modified electrodes is characterized by comprising the following steps of:
step one: carboxylating the multiwall carbon nanotubes by using concentrated nitric acid to obtain carboxylated carbon nanotubes;
step two: deionized water is used as a dispersing agent to prepare the water with the concentration of 1mg mL -1 Is characterized by comprising carboxylated carbon nanotube modifying liquid;
step three: modifying the carboxylated carbon nanotube dispersion liquid on the polished and characterized glassy carbon electrode surface by using a pipetting gun in a direct dripping mode to obtain a carboxylated carbon nanotube modified glassy carbon electrode;
step four: the morphine with unknown concentration is detected by adopting a differential pulse adsorption stripping voltammetry, and the specific operation is as follows: firstly enriching morphine at a certain potential to ensure that morphine is pre-enriched on the surface of an electrode, then detecting by adopting a differential pulse voltammetry, and solving the concentration of morphine in an unknown solution according to the relation between oxidation peak current and the concentration of morphine;
the third step comprises the following steps: by using a three-electrode system, al is passed through 2 O 3 The polished glassy carbon electrode is used as a working electrode and is placed in a reactor containing 5mmol L -1 K 3 [Fe(CN) 6 ]And 0.1mol L -1 Characterization in KCl solution by cyclic voltammetry, when Fe (CN) 6 3-/4- When the oxidation-reduction peak difference is less than 100mV, the electrode can be used continuously; after the surface of the glassy carbon electrode is dried, 4 mu L of carboxylated multiwall carbon nanotubes which are uniformly ultrasonically coated by a liquid-transferring gun are directly dripped on the surface of the treated glassy carbon electrode, the glassy carbon electrode is placed under an infrared lamp for baking for about five minutes, and the carboxylated carbon nanotube-modified glassy carbon electrode is prepared after moisture is volatilized;
the fourth step comprises the following steps: the method comprises the steps of adopting a three-electrode system, adopting a glassy carbon electrode modified by carboxylated carbon nano tubes as a working electrode, adopting Ag/AgCl as a reference electrode, adopting a Pt wire electrode as a counter electrode, adopting a phosphoric acid buffer solution with pH=7.0 as a supporting electrolyte, firstly adopting a chronoamperometry as an enrichment technology, enriching for 300s at a potential of-0.2V, and then adopting a differential pulse voltammetry as a detection technology to detect the oxidation peak current of morphine in the solution.
2. The rapid morphine detection method according to claim 1 wherein step one comprises: weighing 50mg of multi-wall carbon nano tube, placing the multi-wall carbon nano tube into a 250mL round bottom flask, adding 100mL of concentrated nitric acid, stirring in an oil bath at 90 ℃ for reaction for 4 hours, washing with deionized water to be neutral after the reaction is finished, and drying in an oven for later use.
3. The rapid morphine detection method according to claim 1, wherein the second step comprises: weighing 1mg of the carboxylated carbon nanotubes prepared in the step one, adding 1mL of deionized water into a 1.5mL centrifuge tube, and carrying out ultrasonic treatment for 2 hours to uniformly disperse the carboxylated carbon nanotubes to obtain 1mg mL -1 Is characterized by comprising carboxylated carbon nanotube modifying liquid.
4. The rapid morphine detection method based on carboxylated multiwall carbon nanotube modified electrodes of claim 1, further comprising: measuring response peak currents of MOPs with different concentrations by using a differential pulse adsorption stripping voltammetry method, and drawing a standard working curve of the response peak currents; at morphine concentration of 1.0X10 -7 mol L -1 ～1.0×10 -4 mol L -1 In the range of (2), the logarithm lgC of morphine concentration is linearly related to the logarithm lgI of DPV peak current, and the linear regression equation is lgI mu A=0.687 xlgC mu mol L -1 -0.068，r 2 ＝0.992。
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