Detection methods for metal nanoparticles in marine sediments

Abstract

This invention discloses a method for detecting metal nanoparticles in marine sediments, comprising the following steps: (1) mixing the marine sediment to be tested with water to prepare a suspension; (2) centrifuging the suspension to obtain a supernatant, which is a suspension containing metal nanoparticles; (3) performing sp-ICP-MS analysis to determine the concentration and particle size distribution of the metal nanoparticles. The detection method of this invention can extract and determine various common metal nanoparticles, including nanoparticles containing Au, Ag, Cu, Ti, or Zn. This method can detect both the concentration and particle size distribution of metal nanoparticles in sediments, is simple to operate, easy to control, requires a small sample volume, has a low detection limit, and is suitable for the extraction and determination of metal nanoparticles in marine sediments from different regions.

Description

Technical Field

[0001] This invention relates to a method for detecting metallic nanoparticles in marine sediments, belonging to the field of environmental monitoring technology. Background Technology

[0002] Nanoparticles (NPs), especially metallic nanoparticles, have broad application prospects in energy, medicine, and environmental protection. These nanoparticles inevitably enter the environment, and their unique physicochemical properties bring potential ecotoxicological effects and environmental risks. The marine environment, especially nearshore areas, is a major accumulation site for metallic nanoparticles from land and the atmosphere. At the same time, frequent human activities in nearshore environments, such as mariculture, transportation, and tourism, inevitably generate large amounts of metallic nanoparticles. To better assess the pollution status of metallic nanoparticles in nearshore environments, it is urgent to obtain data on their environmental concentration and particle size distribution.

[0003] Currently, single-particle inductively coupled plasma mass spectrometry (ICP-MS) is a powerful tool for quantitatively detecting the concentration and size distribution of metal nanoparticles in environmental samples. However, most existing studies focus on the distribution of metal nanoparticles in freshwater environments (rivers, lakes, etc.), with only three reports on the detection of nanoparticles in marine environments, which only explored the concentration and size distribution of metal nanoparticles in specific areas of seawater. Metal nanoparticles in seawater can undergo both homogeneous and heterogeneous aggregation, eventually settling into sediments. Therefore, the concentration of metal nanoparticles in sediments may be much higher than in seawater. However, due to the lack of effective extraction methods, there are currently no reports on the environmental concentration of metal nanoparticles in marine sediments.

[0004] According to Stokes' theory, under the influence of gravity or centrifugal force, the velocity of particles in a solution is a function of their size and density. Therefore, micron-sized sediment particles can settle before metal nanoparticles under an applied force field, thus achieving separation. Furthermore, the addition of dispersants (such as sodium pyrophosphate) can increase the suspension of nanoparticles, thereby effectively improving the separation efficiency of sediments and metal nanoparticles. However, the addition of dispersants may also interfere with single-particle inductively coupled plasma mass spectrometry (ICP-MS) due to factors such as interference from isobaric elements. Summary of the Invention

[0005] Based on the above-mentioned prior art, the present invention provides a method for detecting metal nanoparticles in marine sediments. This method can simultaneously determine the particle size distribution and concentration of multiple metal nanoparticles in complex sediments, with good detection accuracy, small sample volume required, and low detection limit, making it suitable for the detection of environmental samples.

[0006] This invention is achieved through the following technical solution:

[0007] A method for detecting metallic nanoparticles in marine sediments, comprising the following steps:

[0008] (1) The marine sediment to be tested is mixed with water to form a suspension, wherein the ratio of water to sediment is 1:200 to 1600, in g / mL, preferably 1:1600;

[0009] (2) The above suspension is centrifuged under the following conditions: 10-100×g for 4-8 minutes, preferably 20×g for 5 minutes, to obtain the supernatant, which is the suspension containing metal nanoparticles.

[0010] (3) Sp-ICP-MS analysis was performed to determine the concentration and particle size distribution of the metal nanoparticles.

[0011] Furthermore, the metal nanoparticles are any one or more of the following: Au, Ag, Cu, Ti, or Zn nanoparticles.

[0012] This invention establishes for the first time a method for detecting metal nanoparticles in marine sediments. It can extract and measure various common metal nanoparticles, including those containing Au, Ag, Cu, Ti, or Zn, such as Au, Ag, CuO, TiO2, and ZnO NPs. The method can detect both the concentration and particle size distribution of metal nanoparticles in sediments. This method provides a non-destructive, rapid, and efficient extraction of metal nanoparticles from marine sediments. Combined with sp-ICP-MS detection, it enables simultaneous determination of the particle size distribution and concentration of multiple metal nanoparticles in complex sediments, with high accuracy. The method is simple to operate, easy to control, and widely applicable, suitable for the extraction and determination of metal nanoparticles in marine sediments from different regions. Furthermore, the method requires a small sample volume and has a low detection limit, making it suitable for environmental samples. Attached Figure Description

[0013] Figure 1 Images of gold nanoparticles obtained by electron transmission microscopy, where A represents gold nanoparticles with a diameter of 30 nm; B represents gold nanoparticles with a diameter of 50 nm; and C represents gold nanoparticles with a diameter of 100 nm.

[0014] Figure 2 Figure 1 shows the recovery rate and interference verification results of Method I. A: Recovery rate of sodium pyrophosphate extraction; B: Recovery rate of deionized water extraction; C: sp-ICP-MS determination results of gold nanoparticles in sodium pyrophosphate solution (particle concentration of 25000 particles / mL); D: sp-ICP-MS determination results of gold nanoparticles in sodium pyrophosphate solution (particle concentration of 100000 particles / mL).

[0015] Figure 3 Recovery rates of different solid-liquid ratios and settling times in Method II, where A: solid-liquid ratio; B: settling time. Significant differences existed between treatment groups with different letters (n=4, p<0.05).

[0016] Figure 4 Recovery rates of different solid-liquid ratios and centrifugal forces in Method III, where A: solid-liquid ratio; B: centrifugal force. Significant differences existed between treatment groups with different letters (n=4, p<0.05).

[0017] Figure 5 Recovery rates of gold nanoparticles of different concentrations and sizes in sediments by direct sedimentation and low-speed centrifugation, where A: direct sedimentation; B: low-speed centrifugation.

[0018] Figure 6 Schematic diagram of particle size separation results of gold nanoparticles of different sizes in marine sediments by direct sedimentation and low-speed centrifugation, where A: 30nm; B: 50nm; C: 100nm.

[0019] Figure 7 TEM images of Ag, ZnO, TiO2 and CuONPs, where A, B, C and D are Ag, ZnO, TiO2 and CuONPs, respectively.

[0020] Figure 8 Separation and recovery rates of different metal nanoparticles.

[0021] Figure 9 Particle size distribution of different metal nanoparticles (nanoparticles of the same concentration suspended in deionized water as a standard comparison), where A, B, C, and D are Ag, ZnO, TiO2, and CuO NPs, respectively.

[0022] Figure 10 Flowchart for the detection of different metal nanoparticles in marine sediments. Detailed Implementation

[0023] The present invention will be further described below with reference to embodiments. However, the scope of the present invention is not limited to the following embodiments. Those skilled in the art will understand that various changes and modifications can be made to the present invention without departing from the spirit and scope thereof.

[0024] Unless otherwise specified, the instruments, reagents, and materials used in the following embodiments are all conventional instruments, reagents, and materials already available in the prior art and can be obtained through legitimate commercial channels. Unless otherwise specified, the experimental methods and detection methods used in the following embodiments are all conventional experimental methods and detection methods already available in the prior art.

[0025] Example 1: Detection of Metal Nanoparticles in Marine Sediments

[0026] Based on Stokes' separation theory, this embodiment designs three methods for extracting nanoparticles from marine sediments: (I) Sodium pyrophosphate extraction-sedimentation separation method: Sodium pyrophosphate is used as a dispersant and extracted through sedimentation; (II) Direct sedimentation method: Separation is achieved by utilizing the difference in sedimentation velocity between sediments and nanoparticles; (III) Low-speed centrifugation method: Separation is achieved by utilizing the difference in centrifugation velocity between sediments and nanoparticles.

[0027] In this embodiment, gold nanoparticles (Au NPs) were selected as representative metal nanoparticles, and the extraction method was established by exploring the optimal separation parameters.

[0028] (I) Marine sediments were collected in Laizhou Bay, Bohai Sea (119.87°N, 37.28°E) in May 2021. The collected marine sediments were freeze-dried and ground, and then passed through a 10-mesh stainless steel sieve to remove large particles and biomass (such as shells). 1 g of the processed marine sediment was added to 10 mL of ultrapure water to obtain a marine sediment suspension.

[0029] (ii) Au standard solutions of different sizes were used to investigate gold nanoparticles of three sizes: 28.0±0.9 nm, 50.3±2.3 nm, and 102.2±2.3 nm. Figure 1 (As shown) were added to the above-mentioned marine sediment suspension, placed in a constant temperature shaking chamber (20℃, 150rpm) and mixed thoroughly for 24 hours. After freeze-drying, sediments with nano-Au standard were obtained. The concentrations were 0.04×10⁻⁶. 5 0.2×10 5 4×10 5 6×10 5 8×10 5 particles / mg.

[0030] (III) Extraction was performed using the following extraction methods to obtain the optimal separation parameters.

[0031] Method I: Sodium pyrophosphate was used as a dispersant (with deionized water as a control), and the mixture was dispersed and then extracted by sedimentation. The steps are as follows:

[0032] (1) Add 20.0 mg of Au standard to the sediment (4 × 10⁻⁶) 5 Add 8 mL of sodium pyrophosphate (4 mM) solution (8 mL of deionized water was added to the control) into a 10 mL polypropylene tube, and sonicate (water sonication, 20 °C, 100 W) for 30 minutes to prepare a sediment suspension.

[0033] (2) The above-mentioned sediment suspension was placed in a dark, room-temperature room for sedimentation for 20 hours. After sedimentation, the supernatant 1-2 cm below the surface was collected, and the concentration of Au NPs was determined by single-particle inductively coupled plasma mass spectrometry (sp-ICP-MS). The recovery rate was calculated, and the results are as follows: Figure 2 As shown in Figures A and B, it can be seen that the recovery rate of TSPP extraction (90.1 ± 1.3%) is much higher than that of deionized water extraction (34.9 ± 9.1%).

[0034] The formula for calculating the recovery rate is:

[0035] Among them, C m C0 and C0 represent the concentrations of NPs detected in spiked and unspiked sediments (particles / mL), respectively; V refers to the volume of the supernatant (mL); D is the dilution factor (1-100); M is the mass of the spiked sediment (mg); C s It represents the concentration of spiked particles (particles / mg) in the sediment.

[0036] (3) TSPP interference verification: Two known concentrations of Au standard solutions (2.5 × 10⁻⁶) were tested. 4 and 1.0×10 5 Gold nanoparticles (50 nm) were dissolved in deionized water and TSPP, respectively, and analyzed by sp-ICP-MS (gold nanoparticles suspended in deionized water were used as a standard control). Results are as follows: Figure 2 As shown in C and D, the results indicate that the recoveries of TSSP solutions at both concentrations were very high, at 316.1% and 224.1%, respectively. This suggests that TSSP strongly interferes with the determination. Therefore, Method I is not suitable for the extraction of metal nanoparticles from marine sediments.

[0037] Method II: Direct Settlement Method, the steps are as follows:

[0038] (1) Add 5.0, 10.0, 15.0, 20.0, 30.0 and 40.0 mg of Au-labeled sediment (4 × 10⁻⁶ mg / mL) to 10 mL centrifuge tubes, respectively. 5 Particles / mg, 50nm) and 8mL of deionized water were used to prepare suspensions with different water-to-sediment ratios (1:1600, 1:800, 1:533, 1:400, 1:267, 1:200, g / mL) by sonication in a water bath for 30 minutes.

[0039] (2) The above suspension was placed in a dark, room-temperature room for sedimentation for 4 hours. After sedimentation, a sample of the supernatant 1-2 cm below the surface was taken for sp-ICP-MS analysis, and the recovery rate was calculated. The results are as follows: Figure 3As shown in Figure A, the results indicate that the optimal solid-liquid ratio is 1:533.

[0040] (3) The suspension containing 15.0 mg of spiked sediment (water-sediment ratio 1:533) was settled for 1, 2, 3, 4, 8, and 10 hours, respectively, and sp-ICP-MS was performed to determine the recovery rate. The results are as follows: Figure 3 As shown in Figure B, the optimal settling time was 2 hours, at which point the recovery rate was 66.28 ± 1.98%.

[0041] Method III: Low-speed centrifugation, the steps are as follows:

[0042] (1) Centrifuge the suspension from Method II (20×g, 5min). After centrifugation, take the supernatant 1–2 cm below the liquid surface and perform sp-ICP-MS analysis to calculate the recovery rate. The results are as follows: Figure 4 As shown in Figure A, the results indicate that the optimal solid-liquid ratio is 1:1600.

[0043] (2) The sediment suspensions containing 5.0 mg of sediment (water-sediment ratio of 1:1600) from Method II were centrifuged for 5 min (10, 20, 40, 60, 80, 100 × g) and analyzed by sp-ICP-MS to calculate the recovery rate. The results are as follows: Figure 4 As shown in Figure B. The results indicate that the optimal centrifugal force is 20 × g, at which point the recovery rate is 76.27 ± 4.27%.

[0044] (IV) By determining the optimal separation parameters, extraction methods based on gravity (Method II) and centrifugal force (Method III) were established. Subsequently, recovery rates at different sizes and concentrations were obtained using direct sedimentation (solid-liquid ratio 1:533, sedimentation time 2 hours) and low-speed centrifugation (water-sediment ratio 1:1600, centrifugation parameters: 20×g, 5min), and the results are as follows. Figure 5 As shown in A and B. The results indicate that the recovery rate of high concentrations is higher than that of low concentrations; at the same concentration, the recovery rate of low-speed centrifugation is higher than that of direct sedimentation.

[0045] In addition, the particle size distributions of 30, 50, and 100 nm Au NPs were determined using the established direct sedimentation method and low-speed centrifugation method, respectively. The results are as follows: Figure 6 As shown. By Figure 6 As can be seen from C, compared with the particle size (93.7±2.5nm) measured by method II, the particle size of Au NPs (102.2±2.3nm) measured by method III is closer to that of the standard solution (97.7±0.4nm).

[0046] In summary, low-speed centrifugation is more suitable for extracting metal nanoparticles from marine sediments. The optimal extraction conditions are: water-sediment ratio of 1:1600 g / mL, centrifugal force of 20 × g, and centrifugation time of 5 minutes.

[0047] Example 2: Detection of Metal Nanoparticles in Marine Sediments

[0048] In this embodiment, Au, Ag, ZnO, TiO2, and CuO NPs were selected (Au has an average particle size of 50 nm, Ag has an average particle size of 26.5 nm, ZnO has an average particle size of 55.7 nm, TiO2 has an average particle size of 87.6 nm, and CuO has an average particle size of 68.1 nm). Figure 7 As shown in the image, representative metal nanoparticles were extracted using the following steps:

[0049] 5.12 μL of a suspension containing Au NPs (50 nm, 3.9 × 10⁻⁶) was prepared. 10 The solution containing Au NPs (2 × 10⁻⁶ / mL) was added to a marine sediment suspension (composed of 1 g sediment and 10 mL ultrapure water), and thoroughly mixed in a constant temperature shaking incubator (20 °C, 150 rpm) for 24 h. The mixture was then freeze-dried to obtain Au NPs containing 2 × 10⁻⁶ / mL. 5 Sediments (per mg).

[0050] 10 mg each of Ag NPs, ZnO NPs, TiO2 NPs, and CuO NPs solid powders were added to marine sediment suspensions (composed of 1 g sediment and 10 mL ultrapure water), respectively. The suspensions were then placed in a constant temperature shaking incubator (20°C, 150 rpm) and thoroughly mixed for 24 h. After freeze-drying, sediments containing Ag NPs (10 mg / g), ZnO NPs (10 mg / g), TiO2 NPs (10 mg / g), and CuO NPs (10 mg / g) were obtained. The five types of sediments containing metal nanoparticles were extracted using the low-speed centrifugation method described in Example 1 (extraction conditions: water-sediment ratio 1:1600 g / mL, centrifugal force 20 × g, centrifugation time 5 minutes). The recovery rate and particle size distribution were measured by sp-ICP-MS. The results are as follows: Figure 8 , 9 As shown, the process is as follows: Figure 10 As shown in Table 1, the parameters for single-particle inductively coupled plasma mass spectrometry detection are as follows (other parameters: residence time: 100 μs; sampling time: 60 s; nebulizing gas flow rate: 0.92 mL / min; RF power: 1350 W; auxiliary gas flow rate: 1.2 mL / min; plasma gas flow rate: 15 mL / min).

[0051] Table 1 Detection parameters for single-particle inductively coupled plasma mass spectrometry

[0052]

[0053] Depend on Figure 8 As can be seen, the recoveries of Ag, TiO, CuO, and ZnO NPs were 72.37%, 81.12%, 85.77%, and 84.62%, respectively. Figure 9 As can be seen, the obtained particle sizes are consistent with the results in the electron micrographs.

[0054] Therefore, the method III (low-speed centrifugation) established in Example 1 is also applicable to the extraction of Ag, Zn, Ti and Cu NPs.

[0055] The above embodiments are provided to those skilled in the art to fully disclose and describe how the claimed implementations can be carried out and used, and are not intended to limit the scope of the disclosure herein. Modifications that will be obvious to those skilled in the art will be within the scope of the appended claims.

Claims

1. A method for detecting metallic nanoparticles in marine sediments, characterized in that, The steps are as follows: (1) Mix the marine sediment to be tested with water at a ratio of 1:200 to 1600 to prepare a suspension; (2) Centrifuge the above suspension under the following conditions: 10-100×g, 4-8 minutes, to obtain the supernatant, which is the suspension containing metal nanoparticles. (3) Sp-ICP-MS analysis was performed to determine the concentration and particle size distribution of the metal nanoparticles; The metal nanoparticles are any one or more of Au nanoparticles, Ag nanoparticles, CuO nanoparticles, TiO2 nanoparticles, or ZnO nanoparticles.

2. The method for detecting metal nanoparticles in marine sediments according to claim 1, characterized in that: The detection limit for the concentration of the Au nanoparticles is 45 particles / mL; The detection limit for the concentration of the Ag nanoparticles is 10⁴ particles / mL; The detection limit for the concentration of the CuO nanoparticles is 45 particles / mL; The detection limit for the concentration of the TiO2 nanoparticles is 35 particles / mL; The detection limit for the concentration of the ZnO nanoparticles is 61 particles / mL.

3. The method for detecting metal nanoparticles in marine sediments according to claim 1, characterized in that: The size detection limit of the Au nanoparticles is 17.4 nm; The size detection limit of the Ag nanoparticles is 12.2 nm; The size detection limit of the CuO nanoparticles is 30.4 nm; The size detection limit of the TiO2 nanoparticles is 28.3 nm; The size detection limit of the ZnO nanoparticles is 27.0 nm.

4. The method for detecting metal nanoparticles in marine sediments according to claim 1, characterized in that: The ratio of water to marine sediments is 1:1600.

5. The method for detecting metal nanoparticles in marine sediments according to claim 1, characterized in that: Centrifugation conditions: 20×g, 5 minutes.

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