CN106290537A - The method of L-type Tryptophan concentration in detection solution - Google Patents
The method of L-type Tryptophan concentration in detection solution Download PDFInfo
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- QIVBCDIJIAJPQS-VIFPVBQESA-N L-tryptophane Chemical compound C1=CC=C2C(C[C@H](N)C(O)=O)=CNC2=C1 QIVBCDIJIAJPQS-VIFPVBQESA-N 0.000 title claims abstract description 144
- 238000000034 method Methods 0.000 title claims abstract description 53
- QIVBCDIJIAJPQS-UHFFFAOYSA-N Tryptophan Natural products C1=CC=C2C(CC(N)C(O)=O)=CNC2=C1 QIVBCDIJIAJPQS-UHFFFAOYSA-N 0.000 title claims abstract description 25
- 238000001514 detection method Methods 0.000 title abstract description 10
- 238000001903 differential pulse voltammetry Methods 0.000 claims abstract description 41
- 229910021397 glassy carbon Inorganic materials 0.000 claims abstract description 32
- 229920000858 Cyclodextrin Polymers 0.000 claims abstract description 15
- WHGYBXFWUBPSRW-FOUAGVGXSA-N beta-cyclodextrin Chemical compound OC[C@H]([C@H]([C@@H]([C@H]1O)O)O[C@H]2O[C@@H]([C@@H](O[C@H]3O[C@H](CO)[C@H]([C@@H]([C@H]3O)O)O[C@H]3O[C@H](CO)[C@H]([C@@H]([C@H]3O)O)O[C@H]3O[C@H](CO)[C@H]([C@@H]([C@H]3O)O)O[C@H]3O[C@H](CO)[C@H]([C@@H]([C@H]3O)O)O3)[C@H](O)[C@H]2O)CO)O[C@@H]1O[C@H]1[C@H](O)[C@@H](O)[C@@H]3O[C@@H]1CO WHGYBXFWUBPSRW-FOUAGVGXSA-N 0.000 claims abstract description 15
- 235000011175 beta-cyclodextrine Nutrition 0.000 claims abstract description 15
- 239000001116 FEMA 4028 Substances 0.000 claims abstract description 14
- 229960004853 betadex Drugs 0.000 claims abstract description 14
- 229960004799 tryptophan Drugs 0.000 claims description 75
- 239000000243 solution Substances 0.000 claims description 64
- 239000012086 standard solution Substances 0.000 claims description 44
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- 238000005498 polishing Methods 0.000 claims description 9
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- 238000002484 cyclic voltammetry Methods 0.000 claims description 6
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- 238000001035 drying Methods 0.000 claims description 4
- 239000011259 mixed solution Substances 0.000 claims description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 4
- IFGCUJZIWBUILZ-UHFFFAOYSA-N sodium 2-[[2-[[hydroxy-(3,4,5-trihydroxy-6-methyloxan-2-yl)oxyphosphoryl]amino]-4-methylpentanoyl]amino]-3-(1H-indol-3-yl)propanoic acid Chemical compound [Na+].C=1NC2=CC=CC=C2C=1CC(C(O)=O)NC(=O)C(CC(C)C)NP(O)(=O)OC1OC(C)C(O)C(O)C1O IFGCUJZIWBUILZ-UHFFFAOYSA-N 0.000 claims description 4
- 239000004744 fabric Substances 0.000 claims description 3
- 239000002245 particle Substances 0.000 claims description 3
- 239000008055 phosphate buffer solution Substances 0.000 claims description 3
- 239000000843 powder Substances 0.000 claims description 3
- 238000003756 stirring Methods 0.000 claims description 3
- 229910021607 Silver chloride Inorganic materials 0.000 claims description 2
- 238000011010 flushing procedure Methods 0.000 claims description 2
- 238000002156 mixing Methods 0.000 claims description 2
- 229910052697 platinum Inorganic materials 0.000 claims description 2
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 claims description 2
- 238000012360 testing method Methods 0.000 abstract description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract 1
- 238000005576 amination reaction Methods 0.000 abstract 1
- 229910052799 carbon Inorganic materials 0.000 abstract 1
- 229910021389 graphene Inorganic materials 0.000 abstract 1
- 239000002096 quantum dot Substances 0.000 abstract 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 4
- 230000002209 hydrophobic effect Effects 0.000 description 4
- SEOVTRFCIGRIMH-UHFFFAOYSA-N indole-3-acetic acid Chemical compound C1=CC=C2C(CC(=O)O)=CNC2=C1 SEOVTRFCIGRIMH-UHFFFAOYSA-N 0.000 description 4
- 102000004190 Enzymes Human genes 0.000 description 3
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- 241000196324 Embryophyta Species 0.000 description 2
- 241001465754 Metazoa Species 0.000 description 2
- PVNIIMVLHYAWGP-UHFFFAOYSA-N Niacin Chemical compound OC(=O)C1=CC=CN=C1 PVNIIMVLHYAWGP-UHFFFAOYSA-N 0.000 description 2
- AUNGANRZJHBGPY-SCRDCRAPSA-N Riboflavin Chemical compound OC[C@@H](O)[C@@H](O)[C@@H](O)CN1C=2C=C(C)C(C)=CC=2N=C2C1=NC(=O)NC2=O AUNGANRZJHBGPY-SCRDCRAPSA-N 0.000 description 2
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 2
- 239000002363 auxin Substances 0.000 description 2
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- 241000283690 Bos taurus Species 0.000 description 1
- AUNGANRZJHBGPY-UHFFFAOYSA-N D-Lyxoflavin Natural products OCC(O)C(O)C(O)CN1C=2C=C(C)C(C)=CC=2N=C2C1=NC(=O)NC2=O AUNGANRZJHBGPY-UHFFFAOYSA-N 0.000 description 1
- 206010029400 Nicotinic acid deficiency Diseases 0.000 description 1
- 208000002141 Pellagra Diseases 0.000 description 1
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- 238000007796 conventional method Methods 0.000 description 1
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- 238000000840 electrochemical analysis Methods 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000005538 encapsulation Methods 0.000 description 1
- 150000003278 haem Chemical class 0.000 description 1
- 239000003617 indole-3-acetic acid Substances 0.000 description 1
- 229910001872 inorganic gas Inorganic materials 0.000 description 1
- 229910001410 inorganic ion Inorganic materials 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 230000006651 lactation Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 244000144972 livestock Species 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 235000001968 nicotinic acid Nutrition 0.000 description 1
- 229960003512 nicotinic acid Drugs 0.000 description 1
- 239000011664 nicotinic acid Substances 0.000 description 1
- 235000016709 nutrition Nutrition 0.000 description 1
- 244000144977 poultry Species 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 230000003449 preventive effect Effects 0.000 description 1
- 238000004451 qualitative analysis Methods 0.000 description 1
- 238000004445 quantitative analysis Methods 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 235000019192 riboflavin Nutrition 0.000 description 1
- 229960002477 riboflavin Drugs 0.000 description 1
- 239000002151 riboflavin Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
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- 238000003786 synthesis reaction Methods 0.000 description 1
- 210000001550 testis Anatomy 0.000 description 1
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Classifications
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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
-
- 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)
- Physics & Mathematics (AREA)
- Chemical Kinetics & Catalysis (AREA)
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- Molecular Biology (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
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Abstract
The invention discloses and a kind of detect the method for L-type Tryptophan concentration in solution, three-electrode system is used by differential pulse voltammetry, the L-type tryptophan in solution to be measured to be detected, linear equation according to L-type tryptophan obtains the concentration of L-type tryptophan in solution to be measured, and the working electrode in three-electrode system is the modified glassy carbon electrode that glass-carbon electrode obtains after amination graphene quantum dot and beta cyclodextrin are modified.The method of the present invention can quickly detect L-type Tryptophan concentration, and highly sensitive, accuracy is high.The present invention builds relevant sensing interface as three-electrode system sensor for detecting, use current potential to carry out tryptophan configuration and carry out qualitative, use out peak point current to carry out quantitatively, improve the detection susceptiveness of L-type tryptophan and accuracy, minimum can detect 8.5 × 10‑7The L-type tryptophan of mol/L.The method of the present invention greatly reduces testing cost, simple to operation.
Description
Technical Field
The invention relates to the technical field of detection of isomeric amino acids. More specifically, the invention relates to a method for detecting the concentration of L-tryptophan in a solution by using differential pulse voltammetry based on electrochemical sensing modified by aminated graphene quantum dots and beta cyclodextrin.
Technical Field
Tryptophan is an important precursor for auxin biosynthesis in plants, has a structure similar to that of indoleacetic acid, and is ubiquitous in higher plants. Auxin can be synthesized by tryptophan. The product is an important nutritional agent. Can be involved in plasma protein renewal in animal body, promote riboflavin to exert effect, promote synthesis of nicotinic acid and heme, significantly increase antibody in pregnant animal litter, and promote lactation of lactating cows and sows. When the livestock and poultry lack tryptophan, growth is stagnated, weight is reduced, fat accumulation is reduced, and testis of male breeding stock is atrophied. Can be used as the preventive and therapeutic agent for pellagra.
Because the outer edge of beta cyclodextrin is hydrophilic and the inner cavity is hydrophobic, it can provide a hydrophobic binding site like an enzyme, serving as a host to encapsulate various suitable guests, such as organic molecules, inorganic ions, and gas molecules. The characteristics of hydrophobic inner cavity and hydrophilic outer part enable the complex to form inclusion compounds and molecular assembly systems with a plurality of organic and inorganic molecules according to Van der Waals force, hydrophobic interaction force, matching action among host and object molecules and the like, and become research objects which are interested by chemical and chemical researchers. This selective encapsulation is known as molecular recognition, which results in the formation of host-guest inclusion complexes. Beta-cyclodextrins are the ideal host molecules found to date to resemble enzymes and are themselves characteristic of enzyme models. Therefore, β -cyclodextrin has received great attention and wide application in the fields of catalysis, separation, food, and medicine.
The existing methods for detecting amino acids with different configurations comprise cyclic voltammetry and alternating current impedance, and the methods only perform qualitative and quantitative analysis on one index as a basis, for example, cyclic voltammetry only uses the magnitude of a current signal as the basis for distinguishing the amino acids with different configurations, and alternating current impedance uses the magnitude of resistance as the basis for distinguishing, so that the accuracy is low, the sensitivity is low, and the detection limit is high.
Disclosure of Invention
An object of the present invention is to solve at least the above problems or disadvantages and to provide at least the advantages described hereinafter.
It is still another object of the present invention to provide a method for detecting the concentration of L-tryptophan in a solution, which is capable of rapidly and quantitatively detecting the content of L-tryptophan in a solution, and which establishes a simple, rapid, highly sensitive and accurate method for detecting L-tryptophan.
The invention also aims to provide a preparation method of the working electrode, wherein the glassy carbon electrode modified by the aminated graphene quantum dots and the beta cyclodextrin is used as the working electrode, and the preparation method of the working electrode is simple.
To achieve these objects and other advantages in accordance with the present invention, there is provided a method for detecting the concentration of L-tryptophan in a solution, comprising: the method comprises the steps of constructing a linear equation of L-tryptophan in advance, detecting the L-tryptophan in a solution to be detected by using a three-electrode system consisting of a working electrode, a reference electrode and an auxiliary electrode through differential pulse voltammetry to obtain corresponding parameters, and substituting the corresponding parameters into the linear equation of the L-tryptophan to obtain the concentration of the L-tryptophan in the solution to be detected;
the working electrode is a modified glassy carbon electrode obtained by modifying a glassy carbon electrode through aminated graphene quantum dots and beta cyclodextrin.
Preferably, in the method for detecting the concentration of L-tryptophan in a solution, the method for preparing the modified glassy carbon electrode comprises the following steps:
immersing a reference electrode, an auxiliary electrode and a glassy carbon electrode into a mixed solution containing 1.5-2.5 mg/mL of aminated graphene quantum dots and 1.5-2.5 mg/mL of beta cyclodextrin, and taking out and drying after scanning by a cyclic voltammetry method to obtain the modified glassy carbon electrode;
wherein the scanning parameters are set as: initial potential 0V, highest potential 1V, lowest point 0V, final potential 0V, scanning speed 0.1V/s, scanning times 100 times, sensitivity 10-4A/V, latency 2 s.
Preferably, in the method for detecting the concentration of L-tryptophan in a solution, the pre-constructing a linear equation for L-tryptophan comprises the following steps:
step one, preparing at least 4 parts of standard solution of L-type tryptophan with the concentration of 7.0-30.0 mu mol/L;
step two, detecting each standard solution by using a differential pulse voltammetry to obtain a differential pulse voltammetry curve of each standard solution by using the three-electrode system, and respectively recording the peak value of the current intensity in the differential pulse voltammetry curve of each standard solution in the process;
and step three, drawing a standard curve by taking the peak value of the current intensity corresponding to the obtained differential pulse voltammetry curve of each standard solution as a vertical coordinate and the concentration of each standard solution as a horizontal coordinate, and calculating to obtain a linear equation of the L-type tryptophan.
Preferably, in the method for detecting the concentration of L-tryptophan in the solution, the three-electrode system is adopted, a differential pulse voltammetry is used for detecting the solution to be detected containing L-tryptophan with unknown concentration, a differential pulse voltammetry curve of the solution to be detected is obtained, a peak value parameter of current intensity corresponding to the differential pulse voltammetry curve of the solution to be detected is found, the peak value is substituted into the linear equation of L-tryptophan, and the concentration of L-tryptophan in the solution to be detected is obtained after calculation.
Preferably, in the method for detecting the concentration of L-tryptophan in the solution, the preparation method of the standard solution of L-tryptophan in the first step comprises mixing a phosphate buffer solution with a pH of 6.5-7.5 and a concentration of 10mmol/L and an L-tryptophan solution with a concentration of 0.01mol/L, and then preparing the L-tryptophan solution with a concentration of 7.0 × 10-6mol/L、10.0×10-6mol/L、15.0×10-5mol/L、3.0×10-54 standard solutions in mol/L.
Preferably, in the method for detecting the concentration of L-tryptophan in a solution, the second step specifically comprises the following steps:
1) respectively putting the three-electrode system into the 4 standard solutions, stirring at the room temperature of 20-30 ℃ for 1min, and standing for 1 min;
2) scanning a differential pulse atlas, setting the scanning initial potential to be-0.1V, the termination potential to be 0.6V, the potential increment to be 0.004V, the sample width to be 0.0167s, the amplitude to be 0.05V, the pulse width to be 0.05V and the sensitivity to be 10-4A/V, the waiting time is 2 s;
3) and respectively measuring and recording the peak values of the current intensities of the 4 standard solutions, and establishing differential pulse voltammetry curves of the 4 standard solutions.
Preferably, in the method for detecting the concentration of L-tryptophan in a solution, the aminated graphene quantum dots are obtained by concentrating aminated graphene quantum dots with a concentration of 1mg/mL by a rotary evaporator.
Preferably, in the method for detecting the concentration of L-tryptophan in a solution, the modified glassy carbon electrode is pretreated before use, and the pretreatment comprises the following steps:
placing the modified glassy carbon electrode on polishing cloth containing polishing powder with the particle size of 0.3 mu m and polishing to a mirror surface, and then sequentially placing the glassy carbon electrode in methanol and H with the concentration of 0.5mol/L2SO4And respectively carrying out ultrasonic treatment on the solution and the ultrapure water for 25-35 s, and flushing with the ultrapure water for 0.5-1.5 min after each ultrasonic treatment is finished to obtain the modified glassy carbon electrode.
Preferably, in the method for detecting the concentration of L-tryptophan in a solution, the reference electrode is an Ag/AgCl electrode, and the auxiliary electrode is a platinum electrode.
The invention has the following beneficial effects:
firstly, the method adopts aminated graphene quantum dots and β cyclodextrin modified glassy carbon electrodes to prepare working electrodes, constructs related sensing interfaces to be used as a three-electrode system sensor for detection, adopts potential to carry out tryptophan configuration for qualitative determination, adopts peak current value for quantitative determination, improves the sensitivity and accuracy of L-tryptophan detection, and can detect 8.5 × 10 at the lowest-7L-tryptophan in mol/L.
Secondly, the method is used as a method for electrochemically detecting L-tryptophan by using aminated graphene quantum dots and beta cyclodextrin for fine modification, so that the detection cost is greatly reduced, and the operation is simple and convenient;
finally, the method can rapidly detect the L-tryptophan in one step, and the L-tryptophan can be detected in one step only in a few minutes after the three-electrode system sensor is prepared.
Drawings
FIG. 1 is a differential pulse voltammogram of standard solutions of L-tryptophan at different concentrations in example 1 of the present invention;
FIG. 2 is a graph showing a standard curve of L-tryptophan in example 1 of the present invention.
Detailed Description
The present invention is described in detail below with reference to examples to enable those skilled in the art to practice the invention with reference to the present specification.
It is to be noted that the experimental methods described in the following embodiments are all conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified.
Definitions of terms to which the present invention relates:
unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods, devices, and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods, devices, and materials are now described.
The "working electrode", also known as the research electrode, means that the reaction under study takes place on this electrode. In general, the basic requirements for the working electrode are: the working electrode can be solid or liquid, and various conductive solid materials can be used as the electrode. The electrochemical reaction under study is not affected by the reaction generated by the electrode itself, and the measurement can be carried out in a larger potential area; the electrode must not react with the solvent or electrolyte components; it is preferable that the electrode area is not so large, the electrode surface is uniform and smooth, and surface cleaning and the like can be performed by a simple method. When a solid electrode is used, in order to ensure reproducibility of the experiment, attention must be paid to establishing a proper electrode pretreatment step to ensure redox, surface morphology and a reproducible state without adsorbed impurities.
A method for detecting the concentration of L-tryptophan in a solution comprises the steps of detecting the L-tryptophan in the solution to be detected by a three-electrode system through a differential pulse voltammetry method, obtaining the concentration of the L-tryptophan in the solution to be detected according to a linear equation of the L-tryptophan, and modifying a glassy carbon electrode by using a glassy carbon electrode through modification of aminated graphene quantum dots and beta cyclodextrin to obtain a modified glassy carbon electrode. The three-electrode system consists of a working electrode, a reference electrode and an auxiliary electrode.
The invention adopts the differential pulse voltammetry to detect the L-tryptophan, the differential pulse voltammetry superposes a continuous pulse with constant amplitude and fixed pulse width on a linear scanning waveform, the base potential is scanned from an initial potential to a termination potential in the scanning process, current sampling is carried out before and after the potential pulse starts, and the difference value of the two sampling currents is plotted against the potential, namely a DPV curve, which is mainly used for electrochemical analysis, reduces the background current caused by the oxidation-reduction reaction of impurities, has better detection sensitivity and lower detection limit.
The method for detecting the concentration of the L-tryptophan in the solution comprises the following steps:
step one, preparing the working electrode and building a three-electrode system, and preparing a plurality of L-shaped tryptophan standard solutions with the concentration of 7.0-30.0 mu mol/L;
step two, detecting each standard solution prepared in the step one by using a differential pulse voltammetry to obtain a differential pulse voltammetry curve of each standard solution by using the three-electrode system, and respectively recording the peak value of the current intensity in the differential pulse voltammetry curve of each standard solution in the process;
step three, taking the peak value of the current intensity corresponding to the differential pulse voltammetry curve of each standard solution obtained in the step two as a vertical coordinate, taking the concentration of each standard solution as a horizontal coordinate, drawing a standard curve and calculating a linear equation;
and step four, detecting the solution to be detected containing the L-type tryptophan with unknown concentration by using a differential pulse voltammetry to obtain a differential pulse voltammetry curve of the solution to be detected, substituting the peak value of the current intensity corresponding to the differential pulse voltammetry curve of the solution to be detected into the linear equation obtained in the step three, and calculating to obtain the concentration of the L-type tryptophan in the solution to be detected.
Example 1:
preparing a working electrode: immersing a reference electrode, an auxiliary electrode and a glassy carbon electrode into a mixed solution containing 2mg/mL aminated graphene quantum dots and 2mg/mL beta cyclodextrin, and taking out and drying after scanning by a cyclic voltammetry method to obtain the modified glassy carbon electrode;
wherein the scanning parameters are set as: initial potential 0V, highest potential 1V, lowest point 0V, final potential 0V, scanning speed 0.1V/s, scanning times 100 times, sensitivity 10-4A/V, latency 2 s.
Pretreatment of a working electrode: placing the modified glassy carbon electrode on polishing cloth containing polishing powder with the particle size of 0.3 mu m and polishing to a mirror surface, and then sequentially placing the glassy carbon electrode in methanol and H with the concentration of 0.5mol/L2SO4And respectively carrying out ultrasonic treatment on the solution and the ultrapure water for 30s, and washing with the ultrapure water for 1min after each ultrasonic treatment to obtain the modified glassy carbon electrode.
A method for detecting the concentration of L-tryptophan in a solution comprises the following steps:
step one, preparing the working electrode and building a three-electrode system, and preparing 4 parts of standard solution of L-type tryptophan with the concentration of 7.0-30.0 mu mol/L;
wherein,the preparation method of the working electrode, namely the modified glassy carbon electrode, comprises the steps of immersing a reference electrode, an auxiliary electrode and a pretreated glassy carbon electrode into a mixed solution containing 2mg/mL aminated graphene quantum dots and 2mg/mL β cyclodextrin, taking out and drying after scanning is completed by using a cyclic voltammetry method to obtain the modified glassy carbon electrode, wherein scanning parameters are set to be 0V of initial potential, 1V of highest potential, 0V of lowest point, 0V of final potential, 0.1V/s of scanning speed, 100 times of scanning times and 10 times of sensitivity-4A/V and waiting time of 2 s;
the preparation method of the standard solution of the L-tryptophan in the first step comprises the steps of adding the standard solution of the L-tryptophan with the concentration of 0.01mol/L into the phosphate buffer solution, and respectively preparing the standard solutions of the L-tryptophan with the concentrations of 7.0 × 10-6mol/L solution a, 15.0 × 10-5mol/L solution b, 1.0 × 10-5mol/L solution c, 3.0 × 10-5The total of 4 standard solutions of the mol/L solution d; wherein the pH of the phosphoric acid buffer solution is 7.0, and the concentration of the phosphoric acid buffer solution is 10 mmol/L;
step two, detecting each standard solution prepared in the step one by using a differential pulse voltammetry to obtain a differential pulse voltammetry curve of each standard solution by using the three-electrode system, and respectively recording the peak value of the current intensity in the differential pulse voltammetry curve of each standard solution in the process;
wherein the second step specifically comprises the following steps:
step 2.1, respectively placing the three-electrode system into the 4 standard solutions, stirring for 2min at room temperature, and standing for 2 min;
step 2.2, scanning a differential pulse atlas, setting the scanning initial potential to be-0.1V, the termination potential to be 0.6V, the potential increment to be 0.004V, the sample width to be 0.0167s, the amplitude to be 0.05V, the pulse width to be 0.05V and the sensitivity to be 10-4A/V, the waiting time is 2 s;
and 2.3, respectively measuring and recording the peak values of the current intensities of the 4 standard solutions, and establishing differential pulse voltammetry curves of the 4 standard solutions, wherein the differential pulse voltammetry curves of the 4 standard solutions are shown in fig. 1.
Step three, taking the peak value of the current intensity corresponding to the differential pulse voltammetry curve of the standard solutions a, b, c and d obtained in the step two as the ordinate, taking the concentration of the L-type tryptophan in the solutions a, b, c and d as the abscissa to draw the standard curve and calculate a linear equation; for example, a peak value of the current intensity corresponding to the differential pulse voltammetry of the solution a is used as an ordinate, and the concentration of L-tryptophan in the solution a is used as an abscissa, so that one point on the standard curve can be determined, the solution a is changed into the solutions b, c and d by the above method, and the other three points on the standard curve are determined by the solutions b, c and d, so that the standard curve shown in fig. 2 is drawn;
the linear equation is derived from the standard curve in fig. 2: y is-0.01318-0.00192X, wherein Y is a current value (I), and I is the peak value of the current intensity corresponding to the differential pulse voltammogram of each standard solution and has the unit of μ A; x is the concentration (c) of L-tryptophan in the standard solution in mu mol/L and the correlation coefficient R20.9963, the detection limit of the modified electrode to L-tryptophan was 8.5 × 10-7mol/L；
Step four, adopting the three-electrode system, detecting the solution to be detected containing the L-type tryptophan with unknown concentration by using a differential pulse voltammetry method to obtain a differential pulse voltammetry curve of the solution to be detected, and calculating the concentration of the L-type tryptophan in the solution to be detected: substituting the peak value of the current intensity of the solution to be detected corresponding to the differential pulse voltammetry of the solution to be detected as a Y value into the linear equation, and calculating to obtain the concentration of the L-type tryptophan in the solution to be detected.
While embodiments of the invention have been disclosed above, it is not limited to the applications listed in the description and the embodiments, which are fully applicable in all kinds of fields of application of the invention, and further modifications may readily be effected by those skilled in the art, so that the invention is not limited to the specific details without departing from the general concept defined by the claims and the scope of equivalents.
Claims (9)
1. A method for detecting the concentration of L-tryptophan in a solution, comprising: the method comprises the steps of constructing a linear equation of L-tryptophan in advance, detecting the L-tryptophan in a solution to be detected by using a three-electrode system consisting of a working electrode, a reference electrode and an auxiliary electrode through differential pulse voltammetry to obtain corresponding parameters, and substituting the corresponding parameters into the linear equation of the L-tryptophan to obtain the concentration of the L-tryptophan in the solution to be detected;
the working electrode is a modified glassy carbon electrode obtained by modifying a glassy carbon electrode through aminated graphene quantum dots and beta cyclodextrin.
2. The method for detecting the concentration of L-tryptophan in a solution according to claim 1, wherein the preparation method of the modified glassy carbon electrode comprises the following steps:
immersing a reference electrode, an auxiliary electrode and a glassy carbon electrode into a mixed solution containing 1.5-2.5 mg/mL of aminated graphene quantum dots and 1.5-2.5 mg/mL of beta cyclodextrin, and taking out and drying after scanning by a cyclic voltammetry method to obtain the modified glassy carbon electrode;
wherein the scanning parameters are set as: initial potential 0V, highest potential 1V, lowest point 0V, final potential 0V, scanning speed 0.1V/s, scanning times 100 times, sensitivity 10-4A/V, latency 2 s.
3. The method for detecting the concentration of L-tryptophan in a solution according to claim 2, wherein the pre-constructing a linear equation for L-tryptophan comprises the steps of:
step one, preparing at least 4 parts of standard solution of L-type tryptophan with the concentration of 7.0-30.0 mu mol/L;
step two, detecting each standard solution by using a differential pulse voltammetry to obtain a differential pulse voltammetry curve of each standard solution by using the three-electrode system, and respectively recording the peak value of the current intensity in the differential pulse voltammetry curve of each standard solution in the process;
and step three, drawing a standard curve by taking the peak value of the current intensity corresponding to the obtained differential pulse voltammetry curve of each standard solution as a vertical coordinate and the concentration of each standard solution as a horizontal coordinate, and calculating to obtain a linear equation of the L-type tryptophan.
4. The method for detecting the concentration of L-tryptophan in a solution according to claim 3, wherein the concentration of L-tryptophan in the solution to be detected is obtained by detecting the solution to be detected containing L-tryptophan with unknown concentration by using the three-electrode system and using a differential pulse voltammetry to obtain a differential pulse voltammetry curve of the solution to be detected, finding out a peak value parameter of current intensity corresponding to the differential pulse voltammetry curve of the solution to be detected, substituting the peak value into the linear equation of L-tryptophan, and calculating.
5. The method according to claim 4, wherein the standard solution of L-tryptophan in the first step is prepared by mixing a phosphate buffer solution with a pH of 6.5-7.5 and a concentration of 10mmol/L with a L-tryptophan solution with a concentration of 0.01mol/L, and then preparing L-tryptophan with a concentration of 7.0 × 10-6mol/L、10.0×10-6mol/L、15.0×10-5mol/L、3.0×10-54 standard solutions in mol/L.
6. The method for detecting the concentration of L-tryptophan in a solution according to claim 5, wherein the second step specifically comprises the following steps:
1) respectively putting the three-electrode system into the 4 standard solutions, stirring at the room temperature of 20-30 ℃ for 1min, and standing for 1 min;
2) scanning a differential pulse atlas, setting the scanning initial potential to be-0.1V, the termination potential to be 0.6V, the potential increment to be 0.004V, the sample width to be 0.0167s, the amplitude to be 0.05V, the pulse width to be 0.05V and the sensitivity to be 10-4A/V, the waiting time is 2 s;
3) and respectively measuring and recording the peak values of the current intensities of the 4 standard solutions, and establishing differential pulse voltammetry curves of the 4 standard solutions.
7. The method for detecting the concentration of L-tryptophan in a solution according to claim 1 or 2, wherein the aminated graphene quantum dots are obtained by concentrating aminated graphene quantum dots with a concentration of 1mg/mL by a rotary evaporator.
8. The method for detecting the concentration of L-tryptophan in a solution according to claim 2, wherein the modified glassy carbon electrode is pretreated before use, and the pretreatment comprises the following steps:
placing the modified glassy carbon electrode on polishing cloth containing polishing powder with the particle size of 0.3 mu m and polishing to a mirror surface, and then sequentially placing the glassy carbon electrode in methanol and H with the concentration of 0.5mol/L2SO4And respectively carrying out ultrasonic treatment on the solution and the ultrapure water for 25-35 s, and flushing with the ultrapure water for 0.5-1.5 min after each ultrasonic treatment to obtain the pretreated modified glassy carbon electrode.
9. The method for detecting the concentration of L-tryptophan in a solution according to claim 2, wherein the reference electrode is an Ag/AgCl electrode and the auxiliary electrode is a platinum electrode.
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| US12130253B2 (en) | 2019-11-25 | 2024-10-29 | Changsha University Of Science And Technology | Method for selective detection of L-tryptophan using formaldehyde as medium |
| US11948284B2 (en) | 2020-07-03 | 2024-04-02 | Dalian University Of Technology | 3D modeling method for pore-filling hydrate sediment based on CT image |
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| CN115728281A (en) * | 2022-12-09 | 2023-03-03 | 山西大学 | Fluorescent probe for detecting L-tryptophan and preparation thereof |
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