Magnetic nanoparticle mass concentration measuring method based on nuclear magnetic resonance spectrum chemical shift

Abstract

The invention discloses a magnetic nanoparticle mass concentration measuring method based on nuclear magnetic resonance spectrum chemical shift, and belongs to the technical field of magnetic nano material testing. The relationship between the mass concentration of the magnetic nanoparticles and the magnetic resonance spectrum chemical shift offset is established, and due to the fact that the saturation magnetization intensity of a single magnetic nanoparticle is fixed, the change of the mass concentration of the magnetic nanoparticles is essentially the change of the number of the magnetic nanoparticles. The mass concentration and the magnetic resonance spectrum chemical shift offset have a linear relationship, and the change of the mass concentration of the magnetic nanoparticles can be reflected by measuring the magnetic resonance spectrum chemical shift offset, so that the measurement of the mass concentration of the magnetic nanoparticles is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic nanomaterial testing, and more specifically, relates to a method for measuring the mass concentration of magnetic nanoparticles based on nuclear magnetic resonance spectrum parameters. Background Art

[0002] Magnetic nanoparticles (MNPs) can change the uniformity of the magnetic field, thereby affecting the relaxation rate, which is reflected in the magnetic resonance spectrum as changes in chemical shift and half-width. In practical applications, MNPs are wrapped by surfactants and evenly dispersed in the base liquid to form a stable colloidal suspension. Due to the effect of magnetization, the MNPs in the solution form a certain cluster structure after being magnetized and change the distribution of the magnetic field around themselves, resulting in "local" magnetic field inhomogeneity. This phenomenon changes the magnetic field distribution around the deuterium atoms, causing the degree of offset of their chemical shift to change. Among them, there is a good linear relationship between the mass concentration of magnetic nanoparticles and the offset of chemical shift. In addition, the traditional solution mass concentration measurement method has the problems of extremely high cost, large sample quantity and low applicability while maintaining high precision. Therefore, under the condition that sufficient data has been established through magnetic resonance experiments, in order to achieve adequate utilization of resources, it is entirely possible to use the data obtained in the magnetic resonance experiment to establish the corresponding mass concentration and chemical shift expressions, and realize the function of predicting the mass concentration of the sample reagent to be tested through the chemical shift of the magnetic resonance spectrum. Summary of the invention

[0003] In order to solve the technical problems existing in the prior art, the present invention provides a method for measuring the mass concentration of magnetic nanoparticles based on nuclear magnetic resonance spectroscopy chemical shift. On the basis of magnetic resonance, a mathematical model of magnetic resonance spectroscopy chemical shift and mass concentration is established. With the help of this mathematical model, the mass concentration of the sample can be predicted through the corresponding spectral chemical shift of the sample to be tested.

[0004] To achieve the above object, according to a first aspect of the present invention, a method for measuring the mass concentration of magnetic nanoparticles based on chemical shift of nuclear magnetic resonance spectroscopy is provided, the method comprising the following steps:

[0005] S1. At a set temperature T, use the nuclear magnetic resonance method to measure the pure deuterium water reagent without adding magnetic nanoparticles, and record the value of the chemical shift in the nuclear magnetic resonance spectrum. ;

[0006] S2. Select magnetic nanoparticle reagents with consistent nominal particle sizes, dilute them into reagents of different mass concentrations according to the proportion, perform nuclear magnetic resonance experiments on magnetic nanoparticle reagents at different concentrations, and record the corresponding chemical shift values ​​in the nuclear magnetic resonance spectrum ;

[0007] S3. The sample points corresponding to the mass concentration and chemical shift recorded in S2 are expressed as discrete data points. After linear fitting of the discrete data points, the linear relationship between the chemical shift of the nuclear magnetic resonance spectrum and the mass concentration of the magnetic nanoparticles is obtained under the condition of uniform particle size of the magnetic nanoparticles. ,in, is the slope of the linear relationship between the chemical shift of the nuclear magnetic resonance spectrum and the mass concentration of the magnetic nanoparticles, and C is the mass concentration of the magnetic nanoparticles in the test sample;

[0008] S4. Inverse function of the model in S3 , the relationship between the mass concentration of magnetic nanoparticles and the chemical shift is obtained According to this relationship, the chemical shift of the nuclear magnetic resonance spectrum corresponding to the magnetic nanoparticle reagent with a known concentration is Under the conditions, the mass concentration of the magnetic nanoparticle reagent to be tested can be predicted .

[0009] Preferably, the fluctuation range of the set temperature T during measurement is limited to 280K to 320K.

[0010] Preferably, during the test, the parameters that remain consistent are temperature T, magnetic nanoparticle size d, external magnetic field .

[0011] Through the above scheme conceived by the present invention, the following beneficial effects can be achieved:

[0012] The present invention establishes a linear regression curve by utilizing the correspondence between the parameters of magnetic nanoparticles in magnetic resonance spectroscopy and their concentrations, predicts the mass concentration of a magnetic nanoparticle sample based on the curve, reflects the mass concentration of the magnetic nanoparticles through the chemical shift of the magnetic resonance spectrum, and provides higher mass concentration measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Various other advantages and benefits will become apparent to those skilled in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only used to illustrate the preferred embodiments and are not to be considered as limiting the present invention. In order to more clearly illustrate the technical solution of the present invention, the following is a brief introduction to the drawings required for use in the embodiments, wherein:

[0014] Figure 1A flow chart of a method for measuring mass concentration of magnetic nanoparticles based on chemical shift of nuclear magnetic resonance spectroscopy provided by an embodiment of the present invention;

[0015] Figure 2 The relationship between the sample SHP-05 provided in the embodiment of the present invention and the magnetic resonance chemical shift under different mass concentration conditions;

[0016] Figure 3 The relationship between the sample SHP-10 provided in the embodiment of the present invention and the magnetic resonance chemical shift under different mass concentration conditions;

[0017] Figure 4 The relationship between the sample SHP-15 provided in the embodiment of the present invention and the magnetic resonance chemical shift under different mass concentration conditions;

[0018] Figure 5 The relationship between the sample SHP-20 provided in the embodiment of the present invention and the magnetic resonance chemical shift under different mass concentration conditions;

[0019] Figure 6 The relationship between the sample SHP-25 provided in the embodiment of the present invention and the magnetic resonance chemical shift under different mass concentration conditions;

[0020] Figure 7 The relationship between the sample SHP-30 provided in the embodiment of the present invention and the magnetic resonance chemical shift under different mass concentration conditions;

[0021] Figure 8 The absolute value of the error between the predicted mass concentration and the actual mass concentration of SHP-05 provided in the embodiment of the present invention;

[0022] Fig. 9 The absolute value of the error between the SHP-10 predicted mass concentration and the actual mass concentration provided in the embodiment of the present invention;

[0023] Fig.10 The absolute value of the error between the predicted mass concentration and the actual mass concentration of SHP-15 provided in the embodiment of the present invention;

[0024] Fig.11 The absolute value of the error between the predicted mass concentration and the actual mass concentration of SHP-20 provided in the embodiment of the present invention;

[0025] Fig.12 The absolute value of the error between the predicted mass concentration and the actual mass concentration of SHP-25 provided in the embodiment of the present invention;

[0026] Fig.13 The absolute value of the error between the predicted mass concentration and the actual mass concentration of SHP-30 provided in the embodiment of the present invention; DETAILED DESCRIPTION

[0027] In order to make the purpose and technical solution of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The specific embodiments described here are only used to explain the content of the present invention and are not used to limit the present invention.

[0028] The overall concept of the present invention is to use the relationship between the chemical shift of magnetic nanoparticles in the magnetic resonance spectrum and the mass concentration of magnetic nanoparticles, and calculate the mass concentration of magnetic nanoparticles in the sample through the linear relationship between chemical shift and mass concentration. In nuclear magnetic resonance, magnetic nanoparticles will be magnetized under the action of an external magnetic field to generate an induced magnetic field, which will affect the local magnetic field around itself, resulting in uneven local magnetic field. Changes in the mass concentration of magnetic nanoparticles will cause changes in the induced magnetization intensity of the magnetic nanoparticles in the magnetic field, and the induced magnetic field will affect the distribution of the magnetic field around it, thereby changing the transverse relaxation time of water protons. , during the change of mass concentration, the chemical shift It has a linear relationship with mass concentration through chemical shift The mathematical model of mass concentration can be used to calculate the mass concentration of the sample to be tested.

[0029] like Figure 1 As shown, the present invention provides a method for measuring the mass concentration of magnetic nanoparticles based on nuclear magnetic resonance spectroscopy chemical shift, the method comprising the following steps:

[0030] Step S1. At a set temperature T, use the nuclear magnetic resonance method to measure the pure deuterium water reagent without adding magnetic nanoparticles, and record the value of the chemical shift in the nuclear magnetic resonance spectrum. ;

[0031] In order to obtain the chemical shift of pure deuterated water without adding magnetic nanoparticles, a magnetic resonance experiment was performed on the pure deuterated water reagent using a Spinsolve 60 nuclear magnetic resonance spectrometer to obtain the chemical shift in the magnetic resonance spectrum. , which is the fixed intercept of the linear expression of mass concentration and chemical shift involved in the subsequent steps.

[0032] Step S2. Select a magnetic nanoparticle reagent with a consistent nominal particle size, dilute it into reagents of different mass concentrations according to the ratio, perform nuclear magnetic resonance experiments on the magnetic nanoparticle reagents at different concentrations, and record the corresponding chemical shift values ​​in the nuclear magnetic resonance spectrum ;

[0033] For magnetic nanoparticles with consistent nominal particle size, they are diluted in proportion to obtain magnetic nanoparticle reagents with different mass concentrations. The mass concentration of the magnetic nanoparticles in the reagent is used as the independent variable for magnetic resonance testing. The purpose of recording the chemical shift of its magnetic resonance spectrum is to subsequently establish a linear relationship between the mass concentration of the magnetic nanoparticles and the chemical shift.

[0034] Step S3. The sample points corresponding to the mass concentration and chemical shift recorded in S2 are expressed as discrete data points. After linear fitting of the discrete data points, the linear relationship between the chemical shift of the nuclear magnetic resonance spectrum and the mass concentration of the magnetic nanoparticles is obtained under the condition of uniform particle size of the magnetic nanoparticles. ,in, is the slope of the linear relationship between the chemical shift of the nuclear magnetic resonance spectrum and the mass concentration of the magnetic nanoparticles, and C is the mass concentration of the magnetic nanoparticles in the test sample;

[0035] By testing multiple groups of reagents with different mass concentrations using the magnetic resonance method, multiple discrete sample points of mass concentration and chemical shift were obtained. The linear relationship between the mass concentration of magnetic nanoparticles and the chemical shift can be obtained by fitting the sample points.

[0036] Step S4. Use the inverse function of the model in S3 , the relationship between the mass concentration of magnetic nanoparticles and the chemical shift is obtained According to this relationship, the chemical shift of the nuclear magnetic resonance spectrum corresponding to the magnetic nanoparticle reagent with a known concentration is Under the conditions, the mass concentration of the magnetic nanoparticle reagent to be tested can be predicted ;

[0037] For the sample to be tested, after the magnetic resonance spectroscopy chemical shift corresponding to the magnetic nanoparticles in the reagent is known, The mass concentration can be calculated By comparing the mass concentration of the known sample with the measured value, the measurement deviation is obtained to measure the measurement accuracy.

[0038] Example

[0039] 1. Obtaining magnetic resonance chemical shift without adding magnetic nanoparticle reagent.

[0040] A magnetic resonance experiment was conducted on pure deuterium water reagent, and the chemical shift of its nuclear magnetic resonance spectrum was recorded as .

[0041] 2. Obtaining magnetic nanoparticle reagents with uniform particle size and different mass concentrations.

[0042] SHP series magnetic nanoparticle reagents SHP-05, SHP-10, SHP-15, SHP-20, SHP-25 and SHP-30 (Ocean NanoTech) with nominal core particle sizes of 5 nm, 10 nm, 15 nm, 20 nm, 25 nm and 30 nm were selected. The magnetic nanoparticles used all have Fe3O4 as the magnetic core, and the surface of the magnetic core is coated with a monolayer of oleic acid and a monolayer of amphiphilic polymer, so they have good water solubility and monodispersity;

[0043] The alternative magnetic nanoparticle reagents with mass concentrations of 0.01 mg / mL, 0.025 mg / mL, 0.05 mg / mL, 0.1 mg / mL, and 0.25 mg / mL were selected respectively, and magnetic resonance experiments were carried out on a Spinsolve 60 nuclear magnetic resonance spectrometer. The chemical shift values ​​of the nuclear magnetic resonance spectra were recorded. The linear relationships of the magnetic nanoparticle reagents SHP-05, SHP-10, SHP-15, SHP-20, SHP-25, and SHP-30 at different mass concentrations are shown in the following figure. Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 shown.

[0044] 3. Obtain the linear relationship between chemical shift and mass concentration corresponding to different particle sizes.

[0045] The chemical shift values ​​obtained from the above samples with different mass concentrations are fitted to obtain the form: The linear curves of chemical shift and mass concentration corresponding to particles of different particle sizes are:

[0046]

[0047]

[0048]

[0049]

[0050]

[0051]

[0052] in, In the expression of, is the slope of the linear relationship between the chemical shift of the nuclear magnetic resonance spectrum and the mass concentration of magnetic nanoparticles, C is the mass concentration of magnetic nanoparticles in the test sample, is the correlation coefficient of the linear regression equation, is the experimental condition for obtaining the data of each fitting formula, such as in formula (1) , expressed as In the linear relationship of The value is -12.3275, The corresponding linear relationship under the condition of 4.73 ppm is The correlation coefficient of the linear regression equation in (1) is 0.99988. It shows that it is a fitting formula for the magnetic resonance chemical shift obtained by measuring SHP-05 aqueous solution samples at different mass concentrations using a nuclear magnetic resonance instrument with a main magnetic field of 1.41T.

[0053] 4. Obtaining the mass concentration measurement function.

[0054] The relationship obtained from step 3 , its inverse function It can be expressed as the relationship between the mass concentration of magnetic nanoparticles and the chemical shift , for the sample to be tested, its chemical shift Substitute into the above formula to calculate the mass concentration of the sample .

[0055] 5. Calculated mass concentration The deviation is obtained.

[0056] Using the above , calculate the mass concentration of the sample , and the measured Compare with the mass concentration of known samples to obtain the mass concentration measurement deviation ,like Figure 8 , Fig. 9 , Fig.10 , Fig.11 , Fig.12 , Fig.13 shown.

[0057] From the actual experimental data, we can see that the chemical shift of magnetic nanoreagents has a good linear relationship with mass concentration.

[0058] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for measuring the mass concentration of magnetic nanoparticles based on chemical shift of nuclear magnetic resonance spectroscopy, characterized in that: The method comprises the following steps: S1. At a set temperature T, use the nuclear magnetic resonance method to measure the pure deuterium water reagent without adding magnetic nanoparticles, and record the value of the chemical shift in the nuclear magnetic resonance spectrum. ; S2. Select magnetic nanoparticle reagents with consistent nominal particle sizes, dilute them into reagents of different mass concentrations according to the proportion, perform nuclear magnetic resonance experiments on magnetic nanoparticle reagents at different concentrations, and record the corresponding chemical shift values ​​in the nuclear magnetic resonance spectrum ; The sample points corresponding to the mass concentration and chemical shift recorded in S3.S2 are expressed as discrete data points. After linear fitting of the discrete data points, the linear relationship between the chemical shift of the nuclear magnetic resonance spectrum and the mass concentration of the magnetic nanoparticles is obtained under the condition of uniform particle size of the magnetic nanoparticles. ,in, is the slope of the linear relationship between the chemical shift of the nuclear magnetic resonance spectrum and the mass concentration of the magnetic nanoparticles, and C is the mass concentration of the magnetic nanoparticles in the test sample; S4. Inverse function of the model in S3 , the relationship between the mass concentration of magnetic nanoparticles and the chemical shift is obtained According to this relationship, the chemical shift of the nuclear magnetic resonance spectrum corresponding to the magnetic nanoparticle reagent with a known concentration is Under the conditions, the mass concentration of the magnetic nanoparticle reagent to be tested can be predicted .

2. The method for measuring the mass concentration of magnetic nanoparticles based on nuclear magnetic resonance spectroscopy chemical shift according to claim 1, characterized in that: In S1, the fluctuation range of the temperature T set during measurement is limited to 280 K to 320 K.

3. The method for measuring mass concentration of magnetic nanoparticles based on nuclear magnetic resonance spectroscopy chemical shift according to claim 1, characterized in that: During the test, the parameters that remained consistent were temperature T, magnetic nanoparticle size d, and external magnetic field. .

4. The method for measuring the mass concentration of magnetic nanoparticles based on nuclear magnetic resonance spectroscopy chemical shift according to claim 1, characterized in that: In actual experimental data, under the above conditions, the relationship between chemical shift and mass concentration of magnetic nanoparticles is linear.

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