Magnetic solid-phase extraction material and method for detecting dicofol in water quality samples by using the same

Abstract

The present invention discloses a magnetic solid-phase extraction material and a method for detecting dicofol in water samples by using the same, belonging to the technical field of water sample detection. The technical solution is as follows: Using the magnetic solid-phase extraction material as an adsorbent, dicofol in the water sample is enriched by magnetic solid-phase extraction, and the enriched material is desorbed with a desorbing solution and then detected by liquid chromatography-diode array detector. The present invention enriches dicofol in water samples by magnetic solid-phase extraction, and the target substance in the material is desorbed and then detected and analyzed by liquid chromatography-diode array detector. This method can rapidly and accurately detect dicofol in samples such as surface water and groundwater.

Description

Technical Field

[0001] The present invention belongs to the technical field of water quality sample detection, and particularly relates to a magnetic solid-phase extraction material and a method for detecting dicofol in water quality samples by using the same. Background Art

[0002] Dicofol belongs to one of the persistent organic pollutants and is an organochlorine pesticide. Among them, 4,4-Dicofol is the main component of commercial dicofol, accounting for about 80% of the total amount of dicofol, and the remaining 20% is 2,4’-Dicofol. Dicofol has been widely used in the control of mites on crops such as fruits, vegetables, and tea. In 2019, dicofol was clearly listed in the blacklist of alternative prohibited substances in the Stockholm Convention on Persistent Organic Pollutants. This compound has thermal instability, so there is a certain risk in separating and quantifying dicofol by gas chromatography. Therefore, in order to protect human health and the ecological environment, it is very necessary to determine the content of dicofol in water in an accurate, rapid, economical, and efficient manner.

[0003] In recent years, the research on the removal of pollutants in water by modified environmental mineral materials has been a research hotspot. Magnetite has super strong magnetism and rich surface properties. After the adsorption of pollutants, it is relatively easy to separate from the sample matrix under the condition of an external magnet, so it has a wide application in the removal of pollutants in the environment. The currently used magnetic material is mainly nano-ferroferric oxide. Although the method is relatively mature, due to its too small particle size, the magnetic property is too low after the modification material is coated, and some materials cannot be separated from the sample by a magnet, and the energy consumption required for its co-precipitation process is relatively high, which is not suitable for large-scale low-cost mass production. Therefore, it is very necessary to select a magnetite existing in nature as the core and modify it for the determination of dicofol in the environment. Summary of the Invention

[0004] The present invention provides a magnetic solid-phase extraction material and a method for detecting dicofol in water quality samples by using the same. The magnetic solid-phase extraction material, that is, functionalized magnetite, can detect dicofol in water quality samples more quickly, accurately, and efficiently.

[0005] The technical solution of the present invention is as follows:

[0006] In the first aspect, a method for detecting dicofol in water quality samples by using a magnetic solid-phase extraction material is disclosed. The magnetic solid-phase extraction material is used as an adsorbent, and the dicofol in the water sample is enriched by magnetic solid-phase extraction. After the enriched material is desorbed with a desorbing solution, it is detected by liquid chromatography-diode array detector;

[0007] The magnetic solid-phase extraction material described above is magnetite modified by tetraethyl orthosilicate and octadecyltrimethoxysilane C18;

[0008] The steps of the magnetic solid-phase extraction are as follows: Add the magnetic solid-phase extraction material to the water quality sample, shake and extract, then use a magnet to separate the magnetic solid-phase extraction material from the water quality sample. After adding the desorption solution, dicofol is desorbed into the solvent and detected by liquid chromatography-diode array detector.

[0009] Preferably, the desorption solution is methanol and the desorption time is 30 - 120 s.

[0010] Preferably, the liquid chromatography conditions of the liquid chromatography-diode array detector are as follows: C18 column, column temperature: 30 - 40 °C; flow rate: 1.2 mL / min; injection volume: 10 - 20 μL; detection wavelength: 230 nm; mobile phase: acetonitrile: ultrapure water = 85:15, isocratic elution.

[0011] Preferably, the magnetite is crushed, washed and modified to obtain the magnetic solid-phase extraction material.

[0012] Preferably, the crushing includes coarse crushing, medium crushing and fine crushing; the crushing of the magnetite includes the following steps: Select magnetite ore with mFe / TFe ≥ 85% determined as the raw material, crush the magnetite ore into particles of 5 - 10 mm by a jaw crusher, then put it into a roll crusher to crush it into medium particles of 0.8 - 4 mm, and then put it into a rod mill for fine grinding for 5 h until all particles pass through a 200-mesh sieve to obtain a magnetite sample.

[0013] Preferably, the washing method of the magnetite is as follows: Use 0.1 - 0.2 moL / L dilute hydrochloric acid and deionized water as the cleaning solutions, wash 6 - 8 times in sequence, and then wash 2 - 6 times with absolute ethanol. During the washing process, use an ultrasonic cleaner (power ≥ 40 KHZ), and after washing, dry it for standby.

[0014] Preferably, the modification method of the magnetite is that the magnetite sample uses an ethanol and water mixed solution as the solvent to dissolve ammonia water, tetraethyl orthosilicate and octadecyltrimethoxysilane C18, and first coats SiO 2 on the magnetite particles by the sol-gel method, and then modifies octadecyltrimethoxysilane on the magnetite silica spheres to obtain the magnetic solid-phase extraction material; the mass-volume ratio of the magnetite sample, ammonia water, tetraethyl orthosilicate, and octadecyltrimethoxysilane C18 added is: 10 g: 4 - 6 mL: 1 - 5 mL: 7 - 10 mL.

[0015] Preferably, the method for detecting dicofol in water quality samples using the magnetic solid-phase extraction material includes the following steps:

[0016] 1) Accurately weigh 300 - 500 mg of the magnetic solid-phase extraction material and add it to the water quality sample. The sampling volume of the water quality sample is 100 - 300 mL;

[0017] 2) After adding the magnetic solid-phase extraction material, perform extraction by vortex oscillation. The extraction time is selected to be 120 - 300 s;

[0018] 3) Separate the magnetic solid-phase extraction material and the water quality sample with a magnet, add 1 mL of methanol for elution, and the elution process is vortex for 30 - 120 s;

[0019] 4) After separating the desorption solution and the magnetic solid-phase extraction material with a magnet, transfer it to a volumetric flask and detect it by liquid chromatography - diode array detector.

[0020] In the second aspect, the magnetic solid-phase extraction material described above is disclosed.

[0021] In the third aspect, the application of the magnetic solid-phase extraction material described above in detecting dicofol in water quality samples is disclosed.

[0022] First, crush magnetite. After washing the crushed sample, retain the magnetic components in the ore. Then, use the improved sol - gel method to modify magnetite. First, wrap SiO 2 on the magnetite particles, and then modify octadecyltrimethoxysilane on the magnetite silica spheres and apply it to the determination of dicofol in water.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The preparation method of the present invention is simple, has low energy consumption, and the raw materials are cheap and easily available. The prepared functionalized magnetite material is used as an adsorbent and is successfully applied to the determination of dicofol in water quality samples, with extremely high efficiency and accuracy. The recovery rate of adding dicofol standard solution to the water quality sample is between 78.7% and 102%. Description of the Drawings

[0025] Figure 1 It is the Fourier infrared spectrum diagram of magnetite and functionalized magnetite of the present invention;

[0026] Figure 2 It is the scanning electron microscope diagram of magnetite and functionalized magnetite of the present invention;

[0027] Figure 3Chromatogram of water quality samples and their added dicofol standard solution. Among them, a is the standard curve point of dicofol with a concentration of 2000 ug / L, b is the tap water sample with an added dicofol standard solution concentration of 0.2 ng / mL in Example 2, c is the sample after extraction of the tap water sample in Example 2, d is the sample after extraction of the surface water in Example 6, e is the sample after extraction of the groundwater in Example 8, 1 is 2,4’-Dicofol, and 2 is 4,4’-Dicofol. Detailed implementation manners

[0028] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0029] Example 1

[0030] A method for detecting dicofol in water quality samples using a magnetic solid phase extraction material. The magnetic solid phase extraction material is used as an adsorbent, and dicofol in the water sample is enriched by magnetic solid phase extraction. After the enriched material is desorbed with a desorbing solution, it is detected by liquid chromatography - diode array detector.

[0031] A preparation method of the magnetic solid phase extraction material includes the following steps:

[0032] 1) Select magnetite ore with mFe / TFe = 90% determined through measurement as the raw material.

[0033] 2) Crushing of the magnetite ore: The magnetite ore is crushed into particles of about 5 mm by a jaw crusher, then put into a pair-roll crusher to be crushed into medium particles of about 1 mm, and then put into a rod mill for fine grinding for 5 h until all particles pass through a 200-mesh sieve to obtain a magnetite sample. The size of the magnetite sample is determined by scanning electron microscopy to be less than 20 μm.

[0034] 3) Cleaning of the magnetite: It is successively cleaned 6 times with 0.1 moL / L dilute hydrochloric acid and deionized water, and then cleaned 2 times with absolute ethanol. During the cleaning process, an ultrasonic cleaner (with a power of 40 KHZ) is used. After cleaning, it is dried and reserved.

[0035] 4) Functional modification of magnetite: Weigh 10 g of magnetite that has been ultrasonically cleaned and dried, disperse it in a mixed solution of 400 mL of ethanol and 100 mL of water, add 5 mL of ammonia water, dissolve 5 mL of tetraethyl orthosilicate in 20 mL of ethanol and add it dropwise to the mixed solution. Stir and mix well at 200 r / min at room temperature for 6 h to enhance its adaptability in the complex matrix aqueous solution. Then dissolve 7 mL of octadecyltrimethoxysilane in 20 mL of ethanol, add it dropwise to the mixing container, and stir and mix well at 260 r / min at room temperature for 10 h. After mixing, separate the solid and liquid with a magnet and wash alternately with ethanol and deionized water 12 times. After drying the cleaned material in a vacuum drying oven at 60 °C, mix well to obtain the magnetic solid-phase extraction material. The Fourier transform infrared spectra of magnetite and the magnetic solid-phase extraction material are as shown in Figure 1 shown, and the SEM image of the magnetic solid-phase extraction material is as shown in Figure 2 shown.

[0036] Magnetic solid-phase extraction of water quality samples: Add 500 mg of the magnetic solid-phase extraction material to 100 mL of water quality samples, vortex extract at room temperature for 120 s. Subsequently, separate the adsorbent from the water with a magnet. After removing the water quality samples, add 1 mL of methanol to the adsorbent, vortex for 30 s, use a magnet to separate the desorption solution from the magnetic solid-phase extraction material, load it into an injection vial, and perform qualitative and quantitative analysis of two dicofol by high-performance liquid chromatography with a diode array detector.

[0037] Qualitative and quantitative analysis of two dicofol by high-performance liquid chromatography with a diode array detector is as follows:

[0038] The chromatographic column is a C18 column (150 mm × 2.1 mm, 3.5 µm), column temperature: 30 °C; flow rate: 1.2 mL / min; injection volume: 20 µL; detection wavelength: 230 nm; mobile phase: acetonitrile: ultrapure water = 85:15 isocratic elution.

[0039] Establishment of methodology:

[0040] The prepared functionalized magnetite, i.e., the magnetic solid-phase extraction material, was used as the adsorbent for magnetic solid-phase extraction. The four key factors affecting the solid-phase extraction conditions, namely the dosage of the adsorbent for extraction, the extraction time, the type of desorbing solution, and the volume of the desorbing solution, were optimized in sequence. The optimal experimental conditions were determined as 500 mg of adsorbent, vortex extraction for 120 s to 300 s, and desorption with 1 mL of methanol. A new method for the analysis of dicofol in water samples by magnetic solid-phase extraction - liquid chromatography with diode array detector was established. The established method had good linearity in the concentration range of 20 - 2000 μg / L, and the correlation coefficients R were 0.9999 (2,4’-Dicofol) and 0.9996 (4,4’-Dicofol). When the sampling volume was 100 mL, the method detection limits of 2,4’-Dicofol and 4,4’-Dicofol were 0.041 μg / L and 0.042 μg / L respectively, which were comparable to the method detection limits of dicofol in the current standard. By collecting 30 mL of samples and adding a dicofol standard at a concentration of 0.2 ng / mL, the repeatability of the method was tested. The relative standard deviations within the day and between days were 7.02 - 7.67% and 10.0 - 6.19% respectively. Experiments showed that the functionalized magnetite material could be reused more than 15 times without obvious change in extraction efficiency. The methodological data are shown in Table 1.

[0041] Table 1

[0042]

[0043] For the method of detecting dicofol in water samples using magnetic solid-phase extraction materials, tap water, surface water, and groundwater were used as water samples to detect dicofol in the water samples. Before analysis, the water samples were filtered through a sintered glass funnel to remove particulate impurities in the water. During the actual detection process, since the content of dicofol in the water samples was relatively low, in order to improve the detection accuracy, the method of addition and recovery was adopted. A dicofol standard solution was added to the water samples, and the recovery rate was measured to characterize the extraction effect of the method of the present invention.

[0044] Example 2

[0045] The preparation method of the magnetic solid-phase extraction material was the method described in Example 1;

[0046] The water sample was tap water with a sampling volume of 100 mL, and a 2,4’-Dicofol standard solution and a 4,4’-Dicofol standard solution with a concentration of 0.2 ng / mL were added thereto respectively to form spiked tap water.

[0047] Magnetic solid-phase extraction of water quality samples: Add 500 mg of magnetic solid-phase extraction material to 100 mL of spiked tap water (hereinafter referred to as water quality samples), vortex extract for 120 s at room temperature. Subsequently, separate the adsorbent from the water using a magnet. After removing the water quality samples, add 1 mL of methanol to the adsorbent, vortex for 30 s, use a magnet to separate the desorption solution from the magnetic solid-phase extraction material, transfer it into a sample vial, and perform qualitative and quantitative analysis of two dicofol by high-performance liquid chromatography diode array detector.

[0048] The conditions for qualitative and quantitative analysis of two dicofol by high-performance liquid chromatography diode array detector are the same as those in Example 1. The recovery rate of 2,4’-Dicofol is calculated according to the detection data as shown in the table.

[0049] Example 3

[0050] Different from Example 2, in this example, the added concentrations of 2,4’-Dicofol standard solution and 4,4’-Dicofol standard solution are 2 ng / mL.

[0051] Example 4

[0052] Different from Example 2, in this example, the added concentrations of 2,4’-Dicofol standard solution and 4,4’-Dicofol standard solution are 20 ng / mL.

[0053] Examples 5 - 7

[0054] Different from Examples 2 - 4, in Examples 5 - 7, the water quality samples are 100 mL of surface water, and Examples 5 - 7 correspond to Examples 2 - 4 respectively.

[0055] Examples 8 - 10

[0056] Different from Examples 2 - 4, in Examples 8 - 10, the water quality samples are 100 mL of groundwater, and Examples 8 - 10 correspond to Examples 2 - 4 respectively.

[0057] The added amounts of dicofol standard solution and the recovery rates of 2,4’-Dicofol and 4,4’-Dicofol in Examples 2 - 10 are as shown in Table 1.

[0058] Table 1

[0059]

[0060] In Table 1, a represents that the added concentration of dicofol standard solution is 0.2 ng / mL, b represents that the added concentration of dicofol standard solution is 2 ng / mL, and c represents that the added concentration of dicofol standard solution is 20 ng / mL.

[0061] The recovery rate of adding dicofol standard solution to the water quality sample of the present invention is between 78.7% and 102%. This indicates that the method of the present invention can meet the requirements for the analysis and determination of dicofol in actual samples.

[0062] The present invention has successfully functionalized magnetite, and a new method for analyzing two kinds of dicofol in environmental water samples by magnetic solid-phase extraction - liquid chromatography with diode array detector has been established using this new material. The pretreatment process of this method is simple, fast, and convenient to operate, and there will be no problems such as degradation during the analysis process. The results are reliable and can meet the detection requirements of dicofol in environmental water bodies, and accurate and rapid analysis of two kinds of dicofol in water quality samples can be realized.

[0063] Although the present invention has been described in detail by referring to the accompanying drawings and in combination with preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, those of ordinary skill in the art can make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions should all be within the scope covered by the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for detecting dicofol in water quality samples using a magnetic solid-phase extraction material, characterized in that, using the magnetic solid-phase extraction material as an adsorbent, the dicofol in the water sample is enriched by magnetic solid-phase extraction, and the enriched material is desorbed with a desorbing solution and then detected by liquid chromatography-diode array detector; the magnetic solid-phase extraction material is magnetite modified by tetraethyl orthosilicate and octadecyltrimethoxysilane; the steps of the magnetic solid-phase extraction are as follows: adding the magnetic solid-phase extraction material into the water quality sample, separating the magnetic solid-phase extraction material and the water quality sample by a magnet after shaking extraction, adding the desorbing solution, and desorbing the dicofol into the solvent, and detecting with a liquid chromatography-diode array detector; the desorbing solution is methanol, and the desorbing time is 30 - 120 s; the liquid chromatography conditions of the liquid chromatography-diode array detector are: chromatographic column C18 column, column temperature: 30 - 40 °C; flow rate: 1.2 mL / min; injection volume: 10 - 20 μL; detection wavelength 230 nm; mobile phase: acetonitrile: ultrapure water = 85:15, isocratic elution; the magnetite is obtained by crushing, washing and functional modification to obtain the magnetic solid-phase extraction material; the crushing includes coarse crushing, medium crushing and fine crushing; the crushing of the magnetite includes the following steps: crushing the magnetite ore into particles of 5 - 10 mm by a jaw crusher, then putting it into a pair-roll crusher to crush it into medium particles of 0.8 - 4 mm, and then putting it into a rod mill for fine grinding for 5 h until all particles pass through a 200-mesh sieve to obtain a magnetite sample; the washing method of the magnetite is: using 0.1 - 0.2 moL / L dilute hydrochloric acid and deionized water as cleaning solutions, each washing 6 - 8 times in sequence, and then washing with absolute ethanol 2 - 6 times. During the washing process, an ultrasonic cleaner is used, and after washing, it is dried for standby; The modification method of the magnetite is that the magnetite sample uses a mixed solution of ethanol and water as a solvent to dissolve ammonia water, tetraethyl orthosilicate and octadecyltrimethoxysilane. The sol-gel method is used to first coat SiO 2 on the magnetite particles, and then octadecyltrimethoxysilane is modified on the magnetite silica spheres to obtain a magnetic solid-phase extraction material; the mass-volume ratio of the magnetite sample, ammonia water, tetraethyl orthosilicate, and octadecyltrimethoxysilane is: 10 g: 4 - 6 mL: 1 - 5 mL: 7 - 10 mL.

2. The method for detecting dicofol in water quality samples using a magnetic solid-phase extraction material according to claim 1, characterized in that, it includes the following steps: 1) Accurately weigh 300 - 500 mg of the magnetic solid-phase extraction material and add it to the water quality sample, and the sampling volume of the water quality sample is 100 - 300 mL; 2) After adding the magnetic solid-phase extraction material, perform extraction by vortex oscillation, and the extraction time is selected to be 120 - 300 s; 3) Separate the magnetic solid-phase extraction material and the water quality sample with a magnet, add 1 mL of methanol for elution, and the elution process is vortex for 30 - 120 s; 4) After separating the desorbing solution and the magnetic solid-phase extraction material with a magnet, transfer it to a volumetric flask and detect it with a liquid chromatography-diode array detector.

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