Method for analyzing liquid crystal monomer in indoor dust based on UiO-66-F4 solid phase extraction-high performance liquid chromatography

Abstract

The invention discloses a method for analyzing liquid crystal monomers in indoor dust based on UiO-66-F4 solid phase extraction-high performance liquid chromatography, and belongs to the technical field of analysis and test methods. The UiO-66-F4 is filled into an empty solid-phase extraction small column, and the two ends of the UiO-66-F4 solid-phase extraction small column are compacted by base plates, so that the UiO-66-F4 solid-phase extraction small column is prepared. The pretreatment of the liquid crystal monomer in the indoor dust adopts ultrasonic extraction and solid-phase extraction separation purification, and the treated liquid crystal monomer compound is analyzed and determined by high performance liquid chromatography. According to the method, UiO-66-F4 is used as an adsorption material for solid-phase extraction for the first time, and a novel pollutant liquid crystal monomer in indoor dust is enriched and analyzed. The method is simple in pretreatment process, good in selectivity, low in detection limit, accurate in determination and high in precision.

Description

Technical Field

[0001] The invention belongs to the technical field of analytical testing methods, and specifically relates to a method for 4 The invention discloses a method for determining new pollutant liquid crystal monomer in indoor dust by using adsorption material of solid phase extraction combined with high performance liquid chromatography. Background Art

[0002] Liquid crystal monomers (LCMs) are key materials for display screens of communication equipment, computers and household appliances. Since LCMs in liquid crystal displays are not covalently bonded to the substrate, they are released into the indoor environment during the use of electronic devices and exist in indoor dust, becoming a new type of indoor environmental pollutant. LCMs are persistent, bioaccumulative and biotoxic, which can cause harm to environmental safety and human health. Therefore, accurate monitoring of the content of LCMs in the indoor environment is the basis for indoor pollution evaluation and health effect research.

[0003] Since the determination of LCMs in dust samples has serious interference, sample pretreatment is required to remove interference for accurate quantification. At present, the commonly used pretreatment methods for the analysis of LCMs in complex matrices are mainly Soxhlet extraction or accelerated solvent extraction, followed by purification by gel permeation chromatography, adsorption column chromatography or saponification treatment, which are relatively cumbersome and time-consuming. Therefore, simplifying the pretreatment process and finding enrichment and purification materials with good adsorption effect and strong selectivity are crucial to improving sample analysis efficiency.

[0004] UiO-66 is a classic metal organic framework (MOF) material with advantages such as good stability, strong adsorption capacity and adjustable pore size. It is widely used to adsorb organic pollutants in the environment. However, studies have found that the adsorption capacity of UiO-66 for LCMs is not strong. This may be because its microporous structure limits the accessibility of active sites to a certain extent. If monocarboxylic acid is introduced to construct pore defects during the synthesis of UiO-66, and F atoms are introduced to the ligand to change the structure of UiO-66, UiO-66-F 4 Adsorption material is expected to improve its adsorption capacity for LCMs. 4 Using the adsorbent as solid phase extraction to selectively enrich and separate LCMs in dust can simplify the pretreatment process and improve the analysis efficiency. Summary of the invention

[0005] The present invention provides a method for converting UiO-66-F 4The method is to use the adsorbent material of the solid phase extraction column to enrich and separate LCMs in dust, and then combine it with high performance liquid chromatography for determination. The method comprises the following steps:

[0006] (1)UiO-66-F 4 Preparation of solid phase extraction cartridges:

[0007] Weigh UiO-66-F 4 Fill into the empty solid phase extraction column and press both ends with pads to obtain UiO-66-F 4 Solid phase extraction cartridge, stored in a desiccator for future use; preferably filled with 80-120 mg UiO-66-F 4 ;

[0008] (2) Sample pretreatment

[0009] The indoor dust is pretreated, and the pretreatment process includes two steps of extraction and purification. LCMs are extracted by ultrasonic method and purified by solid phase extraction method using the solid phase extraction column of step (1).

[0010] (3) Determination

[0011] The processed LCMs samples were determined by high performance liquid chromatography

[0012] Further preferred: in step (2) of the method, the sample is pre-treated, the extractant for ultrasonic extraction is acetonitrile, the amount of the extractant is 4 mL, and the extraction time is 20 min. After extraction, centrifuge at 3000 r / min for 5 min to separate the supernatant; repeat the operation twice and combine the supernatants.

[0013] Further preferred: in step (2) of the present method, solid phase extraction is performed using the solid phase extraction column of step (1), and acetonitrile solution is obtained by ultrasonic extraction as the adsorbent, and the eluent is n-hexane-dichloromethane (1:2, v / v); the amount of the adsorbent is 100 mg, and the amount of the eluent is 6 mL;

[0014] After solid phase extraction in step (2), the eluent was blown dry with nitrogen, fixed to volume with 1 mL of acetonitrile, and transferred to a sample bottle for testing.

[0015] During the determination in step (3), the mobile phase of the liquid chromatography is acetonitrile-high purity water, the wavelength of the ultraviolet detector is 225 nm, the column temperature is 30° C., and the flow rate is 1.0 mL / min. The gradient elution program of the mobile phase is: 80% acetonitrile and 20% high purity water from 0 to 3 min, and becomes 100% acetonitrile at the 6th minute.

[0016] During the determination of step (3), the external standard method is used for quantification, and a standard curve is drawn with the concentration of the target compound as the abscissa and the peak area as the ordinate. The concentration of the analyte is quantified according to the standard curve.

[0017] The invention discloses a method based on UiO-66-F 4 The method of solid phase extraction-high performance liquid chromatography for the determination of liquid crystal monomers in indoor dust not only has a simple pretreatment process, accurate determination, and high precision, but also has a better adsorption effect on LCMs and a higher selectivity than commercial HLB solid phase extraction columns. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the HPLC chromatogram of LCMs standard;

[0019] Figure 2 For UiO-66-F 4 HPLC chromatogram of LCMs in solid phase extraction dust;

[0020] Figure 3 This is the HPLC chromatogram of LCMs in dust extracted by HLB column solid phase extraction; DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with examples, but the present invention is not limited to the following examples.

[0022] Example 1: UiO-66-F 4 Preparation of solid phase extraction cartridges

[0023] Weigh 100 mg UiO-66-F 4 (prepared according to the prior art or purchased commercially, etc.) was filled into an empty solid phase extraction column, and both ends were compacted with pads to obtain UiO-66-F 4 Solid phase extraction cartridge. UiO-66-F 4 The preparation process of the adsorbent is as follows: zirconium tetrachloride and 2,3,5,6-tetrafluoroterephthalic acid are mixed in a molar ratio of 1.8:1 to 2:1, added to 40 to 50 mL of acetic acid aqueous solution, ultrasonically dissolved, and transferred to a polytetrafluoroethylene-lined reactor and sealed. The reaction is carried out at a constant temperature of 100 to 120°C for 24 hours. After cooling to room temperature, a white product is obtained by filtration. The obtained white product is washed with DMF and methanol for 3 to 5 times respectively, and vacuum dried at 80°C for 12 hours to obtain UiO-66-F 4 White powder.

[0024] Filled UiO-66-F 4 The solid phase extraction column was stored in a desiccator for future use.

[0025] Example 2: Sample pretreatment conditions

[0026] The extraction agent for ultrasonic extraction was acetonitrile, the dosage was 4 mL, the extraction time was 20 min, and the extraction was repeated three times. The adsorption material for solid phase extraction was UiO-66-F 4 , the dosage is 100 mg, the eluent is n-hexane-dichloromethane (1:2, v / v), the dosage is 6 mL.

[0027] Example 3: Standard curve and detection limit

[0028] Prepare mixed standard solutions of DTMDPB, EFPT, EDPBB, EDPrB, EPB, EBMB, MPCB and MPB at concentrations of 0.5, 1.0, 2.5, 5.0, 10, 20, 50 and 100 mg / L. Perform HPLC determination on mixed standard solutions of LCMs with different concentrations. Draw a standard curve with the target concentration as the abscissa and the peak area as the ordinate.

[0029] A low-concentration mixed standard solution was prepared and measured seven times in parallel. The standard deviation S of the measurement results was calculated, with 3S as the detection limit and 10S as the lower limit of measurement.

[0030] The results are shown in Table 1. The linear range of the method is 0.5-100 mg / L, the correlation coefficient is greater than 0.99, and the linearity is good. The detection limit is in the range of 0.02-0.07 mg / L, and the lower limit of determination is 0.05-0.24 mg / L. It meets the determination requirements.

[0031] Table 1 Standard curves and detection limits of eight LCMs

[0032] Example 4: Precision and Accuracy

[0033] Weigh the indoor dust sample, add 1mL 5mg / L LCMs mixed standard solution, perform sample pretreatment and determination, and calculate the recovery and precision of the method according to formulas 1, 2 and 3. The results are shown in Table 2. The spiked recoveries of the eight LCMs ranged from 82.4% to 101.9%, and the relative standard deviation was less than 6.5%. The recovery and reproducibility of the method were good.

[0034] Formula 1

[0035]

[0036] Formula 2

[0037]

[0038] Formula 3

[0039]

[0040] Table 2 Recovery and precision of LCMs in indoor dust Note: nd. means not detected

[0041] Example 5: Determination of LCMs Standards

[0042] The above method was used to determine the LCMs standard (the concentrations of DTMDPB, MPB, EDPrB, EFPT, EPB, EBMB, EDPBB and MPCB were all 10 mg / L). 4 Solid phase extraction-high performance liquid chromatography analysis showed that the concentrations of eight LCMs were: DTMDPB: 9.44 mg / L; MPB: 8.92 mg / L; EDPrB: 8.45 mg / L; EFPT: 9.41 mg / L; EPB: 8.99 mg / L; EBMB: 8.64 mg / L; EDPBB: 10.41 mg / L; and MPCB: 8.79 mg / L.

[0043] Formula 4

[0044]

[0045] Example 6: Determination of actual dust samples

[0046] 50 mg dust samples were collected in the laboratory and office respectively, and then subjected to ultrasonic extraction and UiO-66-F 4 After solid phase extraction, high performance liquid chromatography was performed, and the concentrations of LCMs compounds in laboratory and office dust were calculated by formula 4. Among them, EPB and EDPBB were detected in both laboratory and office dust samples, with concentrations ranging from 15.50 to 42.70 μg / g, DTMDPB, MPB and EDPrB were only detected in laboratory dust, with concentrations ranging from 4.20 to 24.21 μg / g, while EFPT, EBMB and MPCB were not detected in laboratory and office dust.

Claims

1. A method for analyzing liquid crystal monomers in indoor dust based on UiO-66-F4 solid phase extraction-high performance liquid chromatography, characterized in that: The following steps are involved: (1) Preparation of UiO-66-F4 solid phase extraction column: Weigh UiO-66-F4 and fill it into an empty solid phase extraction column, compact both ends with pads to obtain a UiO-66-F4 solid phase extraction column, and store it in a desiccator for later use; (2) Sample pretreatment Pre-treating the indoor dust, the pre-treatment process includes two steps of extraction and purification, using ultrasonic method to extract LCMs and using solid phase extraction column of step (1) to purify; (3) Determination The treated LCMs samples were determined by high performance liquid chromatography.

2. The method for analyzing liquid crystal monomers in indoor dust based on UiO-66-F4 solid phase extraction-high performance liquid chromatography according to claim 1, characterized in that: The preparation process of the UiO-66-F4 adsorbent in step (1) is as follows: zirconium tetrachloride and 2,3,5,6-tetrafluoroterephthalic acid are mixed in a molar ratio of 1.8:1 to 2:1, added to 40 to 50 mL of acetic acid aqueous solution, ultrasonically dissolved, and transferred to a polytetrafluoroethylene-lined reactor and sealed. The reaction is carried out at a constant temperature of 100 to 120°C for 24 hours. After cooling to room temperature, a white product is obtained by filtration. The obtained white product is washed with DMF and methanol for 3 to 5 times respectively, and vacuum dried at 80°C for 12 hours to obtain UiO-66-F4 white powder.

3. The method for analyzing liquid crystal monomers in indoor dust based on UiO-66-F4 solid phase extraction-high performance liquid chromatography according to claim 1, characterized in that: The extraction agent of the ultrasonic extraction in step (2) is acetonitrile, and the extraction time is 20 minutes; after extraction, the mixture is centrifuged at a speed of 3000 r / min for 5 minutes to separate the supernatant; the operation is repeated twice and the supernatants are combined.

4. The method for analyzing liquid crystal monomers in indoor dust based on UiO-66-F4 solid phase extraction-high performance liquid chromatography according to claim 1, characterized in that: Step (1) is filled with 80-120 mg of UiO-66-F4; Step (2) is solid phase extraction adsorbent used in an amount of 100 mg, eluent is n-hexane-dichloromethane (1:2, v / v), and eluent used in an amount of 6 mL.

5. The method for analyzing liquid crystal monomers in indoor dust based on UiO-66-F4 solid phase extraction-high performance liquid chromatography according to claim 1, characterized in that: The eluate after solid phase extraction in step (2) needs to be blown dry with nitrogen, fixed to volume with 1 mL of acetonitrile, and transferred to a sample bottle for testing.

6. The method for analyzing liquid crystal monomers in indoor dust based on UiO-66-F4 solid phase extraction-high performance liquid chromatography according to claim 1, characterized in that: Step (3) Liquid chromatography conditions: mobile phase is acetonitrile-high purity water, UV detector wavelength is 225 nm, column temperature is 30° C., flow rate is 1.0 mL / min. Gradient elution program of mobile phase is: 80% acetonitrile and 20% high purity water from 0 to 3 min, and becomes 100% acetonitrile at 6 min.

7. The method for analyzing liquid crystal monomers in indoor dust based on UiO-66-F4 solid phase extraction-high performance liquid chromatography according to claim 1, characterized in that: During the analysis of step (3), the external standard method is used for quantitative analysis; the LCMs standard series solutions are measured, and a standard curve is drawn with the concentration as the horizontal axis and the peak area as the vertical axis, and the concentration of the analyte is quantified according to the standard curve.

8. The method for analyzing liquid crystal monomers in indoor dust based on UiO-66-F4 solid phase extraction-high performance liquid chromatography according to claim 1, characterized in that: The liquid crystal monomers (LCMs) are one or more of 4-[difluoro(3,4,5-trifluorophenoxy)methyl]-3,5-difluoro-4'-propyl-biphenyl (DTMDPB), 4"-ethyl-2'-fluoro-4-propyl terphenyl (EFPT), trans-4"-(4-ethoxy-2,3-difluorophenyl)-4-propyl-bicyclohexyl (EDPBB), 1-ethoxy-2,3-difluoro-4-(trans-4-propylcyclohexyl)benzene (EDPrB), trans-4-propylcyclohexyl-4'-ethylbiphenyl (EPB), 1-[4-(4-vinylcyclohexyl)cyclohexyl]-4-toluene (EBMB), trans, trans-4'-p-tolyl-4-propyl-bicyclohexyl (MPCB) and 4'-methyl-4-pentylbiphenyl (MPB).

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