CN108333016A - The method of trace metal and its compound nano-material in separation and concentration water body - Google Patents

Abstract

The invention discloses a kind of methods of trace metal and its compound nano-material in separation and concentration water body based on SPE disks, including：Assemble SPE disks device；Control sample passes through Solid Phase Extraction disk；Utilize Solid Phase Extraction disk described in eluent.Enrichment down to 1000 times of the metal and its compound nano-material of 0.2ng/L can be realized using this method, and the mark-on by this method for nano silver (AgNPs) in four kinds of environment waters measures, it is as a result satisfactory.This method operating procedure is simple, and semi-automatic and speed, which may be implemented, by syringe pump controllably extracts, and applicable sample volume is big, and enrichment times are high.Simultaneously as the pattern and grain size of nano material will not be changed in extraction process, therefore by the way that the primary morphology of trace metal and its compound nano-material in environment water can be obtained after SPE disks separation and concentration nano material.

Description

Method for separating and enriching trace metals and their compound nanomaterials in water

technical field

The invention belongs to the field of environmental analytical chemistry and relates to a method for separating and enriching trace metals and their compound nanomaterials in water bodies based on disc solid phase extraction.

Background technique

Metals and their compound nanomaterials have excellent physical and chemical properties, and have been widely added to daily necessities and industrial products. During the production, use and disposal of these products containing metals and their compound nanomaterials, they will inevitably be released into the environment, causing potential harm to human health, living environment and social safety. Studies have shown that metal and its compound nanomaterials are genotoxic and cytotoxic, and can accumulate in organisms and amplify in the food chain (YJKim, SL Yang, JC Ryu, Mol.Cell.Toxicol.2010, 6, 119-125) . Since the toxicity of metal and its compound nanomaterials is closely related to its particle size, composition and concentration, it is of great significance to accurately characterize, identify and measure metal and its compound nanomaterials. At present, there are transmission electron microscopy (TEM), scanning electron microscopy (SEM) and dynamic light scattering (DLS) methods for measuring metal and its compound nanomaterials; methods for composition identification include ultraviolet-visible absorption spectroscopy (UV-vis), electron energy Quantification is mainly based on particle size separation techniques such as size exclusion chromatography (SEC), field flow fractionation (FFF) and capillary electrophoresis (CE) and inductively coupled plasma Mass spectrometry (ICP-MS) coupled (JF Liu, SJ Yu, YG Yin, et al, Trac-Trends Anal. Chem. 2012, 33, 95-106). However, due to the low content of metal and its compound nanomaterials in environmental water and the complex matrix, these technical methods are actually difficult to meet the characterization, identification and determination of nanomaterials. Therefore, establishing a high-fold separation and enrichment method that can keep the particle size and composition of nanomaterials unchanged can help the high-sensitivity characterization, identification and determination of nanomaterials. Disk-based solid phase extraction (disk-based solid phase extraction, disk-based SPE) is a liquid sample pretreatment technology, its basic principle is the same as that of solid phase extraction, and it is a supplement to solid phase extraction. Disc solid-phase extraction has the characteristics of simple operation, large cross-section, short process, and high enrichment factor. It has been widely used to extract pollutants in large-volume water samples, such as organic pollutants and inorganic metal ions (M Shamsipur, AR Ghiasvand, Y Yamin, Anal. Chem. 1999, 71, 4892-4895). However, there is no report on the separation and enrichment of nanomaterials based on disk solid phase extraction.

Contents of the invention

In order to solve the problems of complex operation and easy to be affected by complex matrix in the separation and enrichment of metal and its compound nanomaterials in the prior art, the present invention proposes a disc-based solid-phase extraction separation and enrichment of trace metal and its compound nanomaterials in water. material method. Using this method, the separation and enrichment of metals and their compound nanomaterials at the ng/L environmental level was achieved, and it was successfully applied to the separation and enrichment of environmental water samples. Moreover, the morphology and particle size distribution of the metal and its compound nanomaterials are basically unchanged before and after enrichment, so the original morphology of the metal and its compound nanomaterials in the environmental water body can be obtained.

The method for separating and enriching trace metals and their compound nanomaterials in water based on disk solid phase extraction proposed by the present invention includes:

Assemble the disk solid phase extraction device;

A control sample is passed through the SPE disc;

The solid phase extraction disc is eluted with an eluent.

Optionally, the metal and its compound nanomaterials include zero-valent metal nanomaterials, metal sulfide nanomaterials or metal oxide nanomaterials.

Optionally, the extraction process is controlled by a syringe pump, negative pressure suction filtration, or hand-push syringe filtration.

Optionally, the solid phase extraction disc is a microporous membrane, and the pore size of the microporous membrane is 0.2-0.8 μm.

Optionally, the material of the microporous membrane is selected from PVDF, polyethersulfone (PES), nylon (Nylon), mixed cellulose (MCE), polytetrafluoroethylene (PTFE) or polypropylene (PP).

Optionally, the sample has a pH of 3.0-9.0 and a volume of 0.1-2.0 L.

Optionally, the eluent is FL-70, and the mass volume concentration of FL-70 is 1.0-10.0%.

Optionally, during elution, the solid-phase extraction disk is placed in the eluent and vortexed at 1500-3500 rpm for 0.5-12h.

Optionally, the method further includes analyzing the isolated and enriched metal and compound nanomaterials, including concentration determination, composition identification and particle size characterization.

Optionally, the analysis uses inductively coupled plasma mass spectrometry to measure the concentration of nanomaterials, and uses transmission electron microscopy, ultraviolet-visible spectroscopy, size exclusion chromatography and inductively coupled plasma mass spectrometry to realize composition identification and particle size characterization of nanomaterials .

Compared with the existing separation and enrichment methods of metal and its compound nanomaterials, this method has the following advantages:

Easy to operate, can realize semi-automatic, speed-controlled extraction;

The sensitivity is high, and the separation and enrichment of nanomaterials as low as 0.2ng/L in water can be realized;

The applicable sample volume is large, which can realize the enrichment of trace nanomaterials in water samples larger than 1L;

The selectivity is good, and the corresponding metal ions in the metal and its compound nanomaterials in the environment basically do not interfere;

Good stability, complex matrix does not interfere with the separation and enrichment of nanomaterials;

The enrichment factor is high, and the enrichment of nanomaterials can be more than 1000 times;

The morphology of nanomaterials remains unchanged after enrichment, and the morphology characterization of trace metals and their compound nanomaterials in the environment can be realized.

Description of drawings

Figure 1 is a schematic diagram of the device of the present invention.

Figure 2 is the effect of microporous membrane on the selective extraction of nano silver.

Figure 3 is the effect of FL-70 concentration, microporous membrane and elution time on the recovery rate of nanomaterials.

Figure 4 shows the effect of sample pH on the selective extraction of metals and their compound nanomaterials.

Figure 5 is the effect of water sample volume on the recovery rate of nanomaterials.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

The method for separating and enriching metals and their compound nanomaterials based on disk solid phase extraction proposed by the present invention includes:

Assemble the disk solid phase extraction device;

A control sample is passed through the SPE disc;

The solid phase extraction disc is eluted with an eluent.

In some embodiments of the present invention, the metal and its compound nanomaterials include zero-valent metal nanomaterials such as nano-silver (AgNPs), nano-gold, nano-palladium, metal sulfide nanomaterials such as nano-silver sulfide, nano-zirconia , nano iron oxide and other metal oxide nanomaterials.

In some embodiments of the present invention, the selection of the device can be controlled by a syringe pump, negative pressure suction filtration, and hand-push syringe filtration can also be used. Finally, the disc solid phase extraction device in the method of the present invention is controlled by a syringe pump, which realizes the semi-automatic and speed-controllable extraction of nanomaterials.

In some embodiments of the present invention, the solid phase extraction disk can be polyvinylidene fluoride (PVDF), polyethersulfone (PES), nylon (Nylon), mixed cellulose (MCE), poly Tetrafluoroethylene (PTFE) and polypropylene (PP) microporous membranes can also be microporous membranes of these materials with other pore sizes. Finally, the solid-phase extraction disk of this method uses a PVDF microporous membrane with a pore size of 0.45 μm to achieve selective enrichment and elution of metals and their compound nanomaterials.

In some embodiments of the invention, the method is useful in a pH range of 3-9. The experiment examines the selectivity of this method for the extraction of metals and their compound nanomaterials in the pH range of 3-9. When the pH of the sample changes in the range of 3-9, the method has no significant change in the extraction of nanomaterials. The test also investigated the influence of the water sample volume on the recovery rate of nanomaterials when the volume of the water sample was changed in the range of 0.1-2.0L, and finally selected 1.0L as the optimal volume.

In some embodiments of the present invention, the optimal concentration of FL-70 as eluent is 2% (m/v). Experimentally investigated the effect of FL-70 on the elution of nanomaterials when the concentration range of 0-10% (m/v) was changed, and finally 2% (m/v) was selected as the optimal concentration.

In some embodiments of the present invention, nanomaterials can be eluted by placing the filter membrane enriched in nanomaterials in the eluent and vortexing at 1500-3500 rpm for 6 hours. The experiment investigated the effect of ultrasound and vortex on the elution of nanomaterials. Although both methods can achieve the elution of nanomaterials, considering the need to keep the nanomaterials unchanged, a relatively mild vortex method was finally selected. The effect of vortex time on the elution of nanomaterials was investigated when the vortex time was changed in the range of 0.5-12h, and finally 6h was selected as the best time.

In some embodiments of the present invention, the method further includes analyzing the isolated and enriched metal and compound nanomaterials, including concentration determination, composition identification and particle size characterization.

During analysis, inductively coupled plasma mass spectrometry can be used to measure the concentration of nanomaterials, and transmission electron microscopy, ultraviolet-visible spectroscopy, size exclusion chromatography and inductively coupled plasma mass spectrometry can be used to realize composition identification and particle size characterization of nanomaterials.

In this method, firstly, the microporous membrane is installed in the replaceable membrane filter head, and the device as shown in Fig. 1 is built. It can be seen from the figure that the automatic and speed-controlled extraction of metals and their compound nanomaterials can be realized through the control of the syringe pump.

Figure 2 is the effect of microporous membrane on the selective extraction of nano silver. Taking AgNPs as an example, the effects of different materials of microporous membranes on the selective extraction of nanomaterials were investigated. It can be seen from the figure that PVDF, PES, Nylon and MCE have the best selectivity to nano-silver, followed by PTFE, and PP is the worst.

Figure 3 is the effect of FL-70 concentration, microporous membrane and elution time on the recovery rate of nanomaterials. Taking AgNPs as an example, the effects of eluent concentration, microporous membrane material and elution time on the recovery of nanomaterials were investigated. It can be seen from the left figure that as the concentration of FL-70 increases, the recovery of nanomaterials adsorbed on different filter membranes increases, and the final concentration of FL-70 is 2% (m/v); The recovery rate of nanomaterials on the membrane is the highest, so the PVDF microporous membrane was finally selected as the solid phase extraction disc. In addition, considering that ultrasound can change the morphology of nanomaterials, the method of the present invention finally chooses a milder vortex mode. As shown in the figure on the right, as the vortex time increases, the recovery rate of nanomaterials increases, and the final vortex time is selected as 6h.

Figure 4 shows the effect of sample pH on the selective extraction of metals and their compound nanomaterials. Taking AgNPs as an example, the influence of the method of the present invention on the selective extraction of nano-silver was investigated in the presence of Ag ⁺ . As shown in the figure, the method of the present invention has good selectivity to nanomaterials in the range of pH 3-9 of the environmental water body.

Figure 5 is the effect of water sample volume on the recovery rate of nanomaterials. Taking AgNPs and river water as examples, the effect of different volumes on the recovery of nanomaterials was investigated. It can be seen from the figure that the recovery rate of nano-silver has no significant difference as the volume increases. However, considering that the larger the volume, the longer the actual operation time, and the 1000-fold enrichment can meet the separation and enrichment of nanomaterials in environmental water samples, the final volume of the sample was selected as 1.0L.

In this method, after the sample is sucked into the syringe, it is pushed out of the syringe at 60 mL/min, and the nanomaterials are selectively adsorbed by the filter membrane. After the 1.0L sample is extracted, take out the filter membrane, transfer to a 1.5mL conical centrifuge tube, add 1.0mL 2% (m/v) FL-70, vortex at 2500rpm for 6h, take out the solution, and proceed to the next step of concentration Determination and Morphological Characterization. Taking AgNPs as an example, the specific implementation of the present invention will be further described through examples.

Example 1: Determination of the addition of AgNPs in actual water

(1) Separation and enrichment of AgNPs in four actual water samples by disc solid phase extraction

Actual water samples do not require any pretreatment. Add AgNPs to 50ng/L in the influent, effluent, river and lake water of a 1.0L sewage treatment plant, shake at 330rpm for ~1h, and use rapid qualitative filter paper to remove some traces of suspended solids in the water. Put the PVDF microporous filter membrane with a pore size of 0.45 μm into the replaceable membrane filter head to build the device shown in Figure 1. After sucking the sample into the syringe, push out the syringe at 60mL/min until all 1.0L of the sample passes through the filter membrane. Take out the filter membrane, transfer it to a 1.5mL conical centrifuge tube, add 1.0mL 2% (m/v) FL-70, vortex at 2500rpm for 6h, take out the solution, and proceed to the next step of concentration determination, composition identification and particle size characterization.

(2) Concentration determination, composition identification and particle size characterization after separation and enrichment of AgNPs

Take 0.8 mL of the enriched and separated AgNPs solution obtained in step (1), add 2.0 mL of 5% (v/v) _HNO3 , and use ICP-MS to measure the concentration of Ag in the solution; take 20 μL of the AgNPs solution obtained in step (1). The enriched and separated AgNPs solution was dropped onto the ultra-thin micro-grid copper grid, and the morphology of the AgNPs was observed by TEM; another 50 μL of the enriched and separated AgNPs solution obtained in step (1) was collected and analyzed by UV-vis and SEC-ICP -MS coupled technology to identify AgNPs and obtain their particle size distribution. The experimental results show that when the concentration of AgNPs in the actual water body is 50ng/L, the recovery rate of AgNPs spiked is above 62%. Considering the complex sample matrix and the extremely low spiked level, the result is quite satisfactory. At the same time, the composition and particle size distribution of Ag nanoparticles in environmental water can be obtained by TEM, UV-vis and SEC-ICP-MS techniques. Therefore, the high-fold enrichment of nanomaterials by this method can realize the concentration determination, composition identification and particle size characterization of trace nanomaterials in environmental water.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention, and are not intended to limit the present invention. Within the spirit and principles of the present invention, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

Claims (10)

1. A method for separating and enriching trace metals and their compound nanomaterials in water bodies, comprising: Assemble the disk solid phase extraction device; A control sample is passed through the SPE disc; The solid phase extraction disc is eluted with an eluent. 2. The method according to claim 1, wherein the metal and its compound nanomaterials comprise zero-valent metal nanomaterials, metal sulfide nanomaterials or metal oxide nanomaterials. 3. The method according to claim 1, wherein the extraction process is controlled by a syringe pump, negative pressure suction filtration or hand-push syringe filtration. 4. The method according to claim 1, wherein the solid phase extraction disk is a microporous membrane, and the pore size of the microporous membrane is 0.2-0.8 μm. 5. method as claimed in claim 4, wherein, the material of described microporous membrane is selected from PVDF, polyether sulfone (PES), nylon (Nylon), mixed cellulose (MCE), polytetrafluoroethylene (PTFE) ) or polypropylene (PP). 6. The method according to claim 1, wherein the sample has a pH value of 3.0-9.0 and a volume of 0.1-2.0L. 7. The method according to claim 1, wherein the eluent is FL-70, and the mass volume concentration of FL-70 is 1.0-10.0%. 8. The method according to claim 1, wherein, during elution, the solid phase extraction disc is placed in the eluent and vortexed at 1500-3500 rpm for 0.5-12h. 9. The method of claim 1, wherein the method further comprises analyzing the isolated and enriched metal and compound nanomaterials, including concentration determination, composition identification and particle size characterization. 10. The method according to claim 9, wherein the analysis adopts inductively coupled plasma mass spectrometry to realize the determination of nanomaterial concentration, and adopts transmission electron microscopy, ultraviolet-visible spectroscopy, size exclusion chromatography and inductively coupled plasma mass spectrometry to realize Composition identification and particle size characterization of nanomaterials.