A method for measuring the mass concentration of magnetic nanoparticles based on the chemical shift of nuclear magnetic resonance spectrum

Abstract

The application discloses a kind of based on magnetic resonance spectroscopy chemical shift's magnetic nano particle mass concentration measurement method, belong to magnetic nanometer material test technical field, the present application with magnetic nano particle induces local magnetic field inhomogeneity and causes magnetic resonance spectrum to produce change as medium, the relationship between the mass concentration of magnetic nano particle and the shift of magnetic resonance spectroscopy chemical shift is established, since the saturation magnetization intensity of single magnetic nano particle is fixed, so the change of the mass concentration of magnetic nano particle is essentially the change of the number of magnetic nano particle, mass concentration and the shift of magnetic resonance spectroscopy chemical shift have linear relationship, the shift of the shift of magnetic resonance spectroscopy chemical shift can reflect the change of the mass concentration of magnetic nano particle, realize the measurement of the mass concentration of magnetic nano particle.

Description

Technical Field

[0001] This invention belongs to the field of magnetic nanomaterial testing technology, and more specifically, relates to a method for measuring the mass concentration of magnetic nanoparticles based on nuclear magnetic resonance spectral parameters. Background Technology

[0002] Magnetic nanoparticles (MNPs) can alter the homogeneity of a magnetic field, thereby affecting the relaxation rate, which is reflected in the magnetic resonance spectrum as changes in chemical shift and full width at half maximum (FWHM). In practical applications, MNPs are encapsulated with surfactants and uniformly dispersed in a base liquid to form a stable colloidal suspension. This suspension is then subjected to an external magnetic field. The magnetization of MNPs in solution leads to the formation of clusters and alters the distribution of the surrounding magnetic field, resulting in localized magnetic field inhomogeneity. This phenomenon changes the magnetic field distribution around deuterium atoms, thus altering the degree of chemical shift. A good linear relationship exists between the mass concentration of magnetic nanoparticles and the chemical shift. However, traditional methods for measuring solution mass concentration, while maintaining high accuracy, suffer from high cost, large sample requirements, and limited applicability. Therefore, given sufficient data obtained through magnetic resonance experiments, to fully utilize resources, it is entirely possible to establish corresponding expressions for mass concentration and chemical shift using the data obtained from magnetic resonance experiments. This allows for the prediction of the mass concentration of the sample reagent using the chemical shift in the magnetic resonance spectrum. Summary of the Invention

[0003] To address the technical problems existing in the prior art, this invention provides a method for measuring the mass concentration of magnetic nanoparticles based on the chemical shift of nuclear magnetic resonance spectroscopy. On the basis of magnetic resonance, a mathematical model of the relationship between the chemical shift of the magnetic resonance spectrum and the mass concentration is established. With the help of this mathematical model, the mass concentration of the sample can be predicted by the corresponding chemical shift of the spectrum of the sample to be tested.

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

[0005] S1. At a set temperature T, the pure deuterium water reagent without the addition of magnetic nanoparticles was measured using nuclear magnetic resonance (NMR), and the chemical shift values ​​in the NMR spectrum were recorded. ;

[0006] S2. Select magnetic nanoparticle reagents with consistent nominal particle size, dilute them to different mass concentrations according to the specified ratio, and perform nuclear magnetic resonance experiments on the magnetic nanoparticle reagents at different concentrations, recording the corresponding chemical shift values ​​in the nuclear magnetic resonance spectra. ;

[0007] S3. The sample points corresponding to the mass concentration and chemical shift recorded in S2 are represented 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 magnetic nanoparticle size. ,in, denoted as the slope of the linear relationship between the chemical shift in the nuclear magnetic resonance spectrum and the mass concentration of magnetic nanoparticles, where C is the mass concentration of magnetic nanoparticles in the test sample.

[0008] S4. Using the inverse function of the model in S3 The relationship between the mass concentration of magnetic nanoparticles and chemical shift was obtained. According to this relationship, the nuclear magnetic resonance spectral chemical shift corresponding to the known concentration of magnetic nanoparticle reagent is... Under these 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 testing process, the following parameters are kept constant: temperature T, magnetic nanoparticle size d, and external magnetic field. .

[0011] The above-described solutions conceived in this invention can achieve the following beneficial effects:

[0012] This invention establishes a linear regression curve by utilizing the correspondence between the parameters and concentration of magnetic nanoparticles in magnetic resonance spectroscopy. Based on this curve, the mass concentration of magnetic nanoparticle samples is predicted. The mass concentration of magnetic nanoparticles is reflected by the chemical shift of the magnetic resonance spectrum, providing high accuracy in the measurement of mass concentration. Attached Figure Description

[0013] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. To more clearly illustrate the technical solutions of the invention, the drawings used in the embodiments will be briefly described below, wherein:

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

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

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

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

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

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

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

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

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

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

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

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

[0026] Figure 13 The absolute value of the error between the predicted mass concentration and the actual mass concentration provided by the SHP-30 in the embodiments of the present invention; Detailed Implementation

[0027] To make the objectives and technical solutions of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are only used to explain the content of this invention and are not intended to limit this invention.

[0028] The overall concept of this invention is as follows: Utilizing the relationship between the chemical shift of magnetic nanoparticles in magnetic resonance spectroscopy and their mass concentration, the mass concentration of magnetic nanoparticles in a sample is calculated through the linear relationship between chemical shift and mass concentration. In nuclear magnetic resonance (NMR), magnetic nanoparticles are magnetized under the influence of an external magnetic field, generating an induced magnetic field that affects the surrounding local magnetic field, leading to local magnetic field inhomogeneity. Changes in the mass concentration of magnetic nanoparticles cause changes in the induced magnetization intensity of the nanoparticles in the magnetic field. This induced magnetic field affects the distribution of the surrounding magnetic field, thereby altering the transverse relaxation time of water protons. During the process of mass concentration change, chemical shift It has a linear relationship with mass concentration, through chemical shift. A 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, this invention provides a method for measuring the mass concentration of magnetic nanoparticles based on the chemical shift of nuclear magnetic resonance spectroscopy. The method includes the following steps:

[0030] Step S1. At a set temperature T, the pure deuterium water reagent without the addition of magnetic nanoparticles is measured using nuclear magnetic resonance (NMR), and the chemical shift value in the NMR spectrum is recorded. ;

[0031] To obtain the chemical shift of pure deuterium water without the addition of magnetic nanoparticles, magnetic resonance experiments were performed on the pure deuterium water reagent using a Spinsolve 60 nuclear magnetic resonance spectrometer to obtain the chemical shift in the magnetic resonance spectrum. This value is the fixed intercept of the linear expression of mass concentration versus chemical shift involved in subsequent steps.

[0032] Step S2. Select magnetic nanoparticle reagents with consistent nominal particle size, dilute them to different mass concentrations according to the specified ratio, and perform nuclear magnetic resonance experiments on the magnetic nanoparticle reagents at different concentrations, recording the corresponding chemical shift values ​​in the nuclear magnetic resonance spectra. ;

[0033] For magnetic nanoparticles with the same nominal particle size, they were diluted proportionally to obtain magnetic nanoparticle reagents with different mass concentrations. The mass concentration of magnetic nanoparticles in the reagents was used as the independent variable for magnetic resonance testing. The purpose of recording the chemical shift of the magnetic resonance spectrum was to establish a linear relationship between the mass concentration of magnetic nanoparticles and the chemical shift in the future.

[0034] Step S3. The sample points corresponding to the mass concentration and chemical shift recorded in S2 are represented 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 magnetic nanoparticle size. ,in, denoted as the slope of the linear relationship between the chemical shift in the nuclear magnetic resonance spectrum and the mass concentration of magnetic nanoparticles, where C is the mass concentration of magnetic nanoparticles in the test sample.

[0035] Multiple groups of reagents with different mass concentrations were tested using magnetic resonance imaging, resulting in discrete sample points showing the relationship between mass concentration and chemical shift. By fitting these sample points, a linear relationship between the mass concentration and chemical shift of the magnetic nanoparticles could be obtained.

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

[0037] For a sample with a known mass concentration, given the known chemical shift of the magnetic nanoparticles in the reagent, the magnetic resonance spectrum is then analyzed using... Mass concentration can be calculated The measurement deviation is obtained by comparing it with the mass concentration of a known sample, and this deviation is used to measure the measurement accuracy.

[0038] Example

[0039] 1. Obtaining the magnetic resonance chemical shift without the addition of magnetic nanoparticle reagents.

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

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

[0042] The 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 5nm, 10nm, 15nm, 20nm, 25nm and 30nm were selected. The magnetic nanoparticles used all have Fe3O4 as the magnetic core and are coated with a single layer of oleic acid and a single layer of amphiphilic polymer on the surface of the magnetic core, thus having good water solubility and monodispersity.

[0043] Candidate 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, and magnetic resonance experiments were performed on a Spinsolve 60 NMR spectrometer. The chemical shift values ​​of their NMR spectra were recorded. The linear relationships of magnetic nanoparticle reagents SHP-05, SHP-10, SHP-15, SHP-20, SHP-25, and SHP-30 at different mass concentrations are shown below. Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 As shown.

[0044] 3. Obtaining the linear relationship between chemical shift and mass concentration for different particle sizes.

[0045] The chemical shift values ​​obtained from the samples with different mass concentrations were fitted to obtain the following form: The linear curves of chemical shift versus mass concentration for particles of different sizes are as follows:

[0046]

[0047]

[0048]

[0049]

[0050]

[0051]

[0052] in, In the expression, where, denoted as , where is the slope of the linear relationship between the chemical shift in the nuclear magnetic resonance spectrum and the mass concentration of magnetic nanoparticles, and C is the mass concentration of magnetic nanoparticles in the test sample. The correlation coefficient is the coefficient of the linear regression equation. These are the experimental conditions for obtaining the data for each fitting equation, as shown in equation (1). , represented as In a linear relationship, The value is -12.3275. The linear relationship corresponding to a concentration of 4.73 ppm is... The correlation coefficient of the corresponding linear regression in (1) is 0.99988. This indicates that the magnetic resonance chemical shift was obtained by measuring SHP-05 aqueous solution samples at different mass concentrations using a nuclear magnetic resonance spectrometer with a main magnetic field of 1.41T.

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

[0054] The relation obtained in step 3 Its inverse function This 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 Substituting into the above formula, the mass concentration of the sample can be calculated. .

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

[0056] Using the above The mass concentration of the sample was calculated. and the measured The mass concentration measurement deviation is obtained by comparing it with the mass concentration of a known sample. ,like Figure 8 , Figure 9 , Figure 10 , Figure 11 , Figure 12 , Figure 13 As shown.

[0057] The actual experimental data show that the chemical shift of the magnetic nanoreagent has a good linear relationship with the mass concentration.

[0058] Those skilled in the art will readily understand that the above description is merely 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 within the scope of protection of the present invention.

Claims

1. A method for measuring the mass concentration of magnetic nanoparticles based on the chemical shift of nuclear magnetic resonance spectroscopy, characterized in that, The method includes the following steps: S1. At a set temperature T, the pure deuterium water reagent without the addition of magnetic nanoparticles was measured using nuclear magnetic resonance (NMR), and the chemical shift values ​​in the NMR spectrum were recorded. ; S2. Select magnetic nanoparticle reagents with consistent nominal particle size, dilute them to different mass concentrations according to the specified ratio, and perform nuclear magnetic resonance experiments on the magnetic nanoparticle reagents at different concentrations, recording the corresponding chemical shift values ​​in the nuclear magnetic resonance spectra. ; S3. The sample points corresponding to the mass concentration and chemical shift recorded in S2 are represented 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 magnetic nanoparticle size. ,in, denoted as the slope of the linear relationship between the chemical shift in the nuclear magnetic resonance spectrum and the mass concentration of magnetic nanoparticles, where C is the mass concentration of magnetic nanoparticles in the test sample. S4. Using the inverse function of the model in S3 The relationship between the mass concentration of magnetic nanoparticles and chemical shift was obtained. According to this relationship, the nuclear magnetic resonance spectral chemical shift corresponding to the known concentration of the magnetic nanoparticle reagent is... Under these 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 the chemical shift of nuclear magnetic resonance spectroscopy according to claim 1, characterized in that, In S1, the temperature T set during measurement is limited to a fluctuation range of 280 K to 320 K.

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

4. The method for measuring the mass concentration of magnetic nanoparticles based on the chemical shift of nuclear magnetic resonance spectroscopy according to claim 3, characterized in that, In actual experimental data, temperature T, magnetic nanoparticle size d, and external magnetic field... Under consistent conditions, the relationship between chemical shift and the mass concentration of magnetic nanoparticles is linear.

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