Method for determining plasticizer in urban sewage

Abstract

The invention provides a gas chromatography method for determining a plasticizer in urban sewage, which comprises the following steps: (1) taking a water sample of the urban sewage, filtering by using filter paper and a filter membrane in sequence, storing in a refrigerator at 4 DEG C, and finishing pretreatment within 24 hours; (2) activating and balancing a solid-phase extraction column, and carrying out solid-phase extraction on the water sample; (3) eluting by using a mixed solution of dichloromethane and methanol as an eluent, blow-drying the eluent by using nitrogen, and fixing the volume for detection; and (4) detecting the content of the plasticizer in the to-be-detected liquid by adopting gas chromatography-mass spectrometry / mass spectrometry online detection. The method for detecting the plasticizer in the municipal sewage, provided by the invention, has the characteristics of simple treatment method, high detection efficiency and easiness in operation.

Description

Technical Field

[0001] The invention relates to a method for determining plasticizers in urban sewage. Technical Background

[0002] Plasticizers are additives that increase the plasticity of plastic products and are often used in building materials, clothing, furniture, and pharmaceutical products. Plasticizers are phthalates (PAEs), a general term for a large class of fat-soluble compounds, and are classified as Class IV toxic chemicals. In daily life, they come from several sources, including migration from the environment to the food chain, migration to food through food packaging, and illegal additions. Products that widely contain plasticizers include children's toys made of PVC, cosmetics such as perfumes and nail polishes that women often use (to preserve the scent of the fragrance or make the nail polish film smoother), and various plastic food packaging materials.

[0003] Research has shown that PAEs, a class of environmental hormones characterized by their diverse composition, resistance to degradation, and high bioaccumulation, can disrupt the human endocrine system. With the widespread production and use of phthalates, PAEs are now ubiquitous in the atmosphere, water, sediments, soil, and organisms, and phthalate pollution has garnered widespread global attention.

[0004] Currently, the main pretreatment methods for water samples include liquid-liquid extraction, solid-phase extraction, and solid-phase microextraction. The drinking water hygiene standard GB5750-2006 uses liquid-liquid extraction, but liquid-liquid extraction not only requires large amounts of organic solvents and is cumbersome to operate, but also has a low recovery rate.

[0005] Finding a convenient, fast and accurate method for determining phthalate esters has been one of the research hotspots in recent years. Summary of the Invention

[0006] The present invention overcomes the deficiencies in the prior art and provides a method for detecting divalent phthalates in municipal sewage; the method has the characteristics of high efficiency, simple sample pretreatment, and convenient operation.

[0007] The technical solution adopted in the present invention is as follows:

[0008] A method for determining plasticizers in municipal sewage comprises the following steps:

[0009] (1) Take a municipal sewage sample, filter it with filter paper, filter it with a membrane, store it at 4°C, and complete solid phase extraction within 24 hours;

[0010] (2) Activate the solid phase extraction cartridge to enrich phthalates in the filtered water sample;

[0011] (3) Use a mixed solution of dichloromethane and methanol as the eluent for elution. After the eluate is dried with nitrogen, it is made up to volume with methanol for testing.

[0012] (4) Use gas chromatography - mass spectrometry / mass spectrometry (GC - MS / MS) to detect the phthalate content in the test solution.

[0013] In the present invention, a mixed solution of dichloromethane and methanol is used as the eluent, and the recovery rates of two phthalates can both reach a relatively high level.

[0014] Under optimized conditions, in step (1), adjust the pH of the urban sewage water sample to about 2.0 before filtration, and the recovery rates can both reach a relatively high level.

[0015] Under optimized conditions, in step (2), select a reversed - phase packing with a stationary phase of C18 for the solid - phase extraction cartridge. Activate it successively with dichloromethane and methanol, and equilibrate the cartridge with ultrapure water.

[0016] Under optimized conditions, in step (3), the volume ratio of dichloromethane to methanol in the eluent is 7:3.

[0017] In step (3), for 0.5 L of water sample, 8 mL of eluent is used.

[0018] In step (3), after adding the eluent to the solid - phase extraction column, let it stand for 5 min first, and then carry out elution. <C

[0019] In step (4), the chromatographic conditions are as follows: the chromatographic column is HP - 5MS; the inlet temperature is 250 °C; the carrier gas is helium; the flow rate is 1.2 mL / min, splitless injection, and the injection volume is 1 μL.

[0020] The mass spectrometry conditions for gas chromatography - mass spectrometry / mass spectrometry (GC - MS / MS) detection are as follows: the ionization mode is electron impact ionization source (EI), the ionization energy is 70 eV, the ion source temperature is 230 °C; the transfer line temperature is 280 °C; the solvent delay time is 7 min, the mass spectrometry qualitative analysis adopts the full - scan (SIM) mode, the scanning range is 50 - 500 m / z, and the quantitative analysis adopts the multiple reaction monitoring (MRM) mode.

[0021] The programmed temperature conditions for gas chromatography - mass spectrometry / mass spectrometry (GC - MS / MS) detection in step (4) are as follows: the initial column temperature is 50 °C, hold for 1 min, then increase the temperature to 180 °C at a rate of 20 °C / min and hold for 5 min; then increase the temperature to 220 °C at a rate of 20 °C / min and hold for 5 min; then increase the temperature to 260 °C at a rate of 20 °C / min; hold for 5 min; then increase the temperature to 280 °C at a rate of 20 °C / min and hold for 5 min.

[0022] The technical solution provided by the present invention has the following advantages:

[0023] 1. Using solid-phase extraction (SPE) as the pretreatment method, it has less consumption of organic solvents and good enrichment effect of the target substances.

[0024] 2. The present invention takes diethyl phthalate (DEP) and dibutyl phthalate (DBP) as the research objects, uses solid-phase extraction and gas chromatography-mass spectrometry / mass spectrometry (GC-MS / MS) for quantification, and applies it to the determination of phthalic acid esters in urban sewage of a certain urban sewage treatment plant in Changchun City, providing a basis for establishing a reliable detection method.

[0025] 3. The present invention enriches the test methods for phthalic acid esters in urban sewage and establishes a reliable analysis method for phthalic acid esters. Description of the Drawings

[0026] Figure 1 It is the GC-MS / MS chromatogram of diethyl phthalate (DEP) and dibutyl phthalate (DBP). Detailed Embodiments

[0027] The present invention provides a method for determining phthalic acid esters in urban sewage, and the main steps are as follows:

[0028] (1) Take the urban sewage water sample, filter it once with filter paper and filter membrane, adjust the pH to about 2.0, store it at 4 °C, and complete the solid-phase extraction within 24 hours.

[0029] (2) Select a reversed-phase packing with a stationary phase of C18 for the solid-phase extraction column, activate it successively with dichloromethane and methanol, and equilibrate the column with ultrapure water.

[0030] (3) Enrich phthalic acid esters in the filtered water sample with the activated column.

[0031] (4) Use a mixed solution with a volume ratio of dichloromethane to methanol of 7:3 as the eluent for elution. After the eluate is dried with nitrogen, it is fixed with methanol for measurement; use gas chromatography-mass spectrometry / mass spectrometry to detect the content of phthalic acid esters in the test solution.

[0032] The inventors of the present application optimized the pretreatment conditions and chromatographic conditions.

[0033] 1. Volume ratio of dichloromethane to methanol in the eluent

[0034] Select volume ratios of dichloromethane to methanol of 5:5, 6:4, 7:3, and 8:2 for elution comparison of the target substances. When the ratio is 7:3, the recovery rate is the highest.

[0035] 2. Column temperature of the chromatographic conditions

[0036] The initial column temperature is 50 or 60 °C, held for 1 min, then heated at 15 or 20 °C / min to 180 °C and held for 5 min; then heated at 20 °C / min to 220 °C and held for 5 min; then heated at 20 °C / min to 260 °C; held for 5 min; then heated at 20 °C / min to 260, 270 or 280 °C and held for 5 min. According to the chromatographic resolution of the actual water sample spiked, the column temperature is determined as: the initial column temperature is 50 °C, held for 1 min, heated at 20 °C / min to 180 °C and held for 5 min; then heated at 20 °C / min to 220 °C and held for 5 min; then heated at 20 °C / min to 260 °C; held for 5 min; then heated at 20 °C / min to 280 °C and held for 5 min.

[0037] 3. Determination of phthalic acid esters in urban sewage by GC-MS / MS

[0038] 3.1 Gas chromatography conditions

[0039] Agilent HP-5MS + backflush EPC + Agilent HP-5MS. The inlet temperature is 250 °C and the injection volume is 1 μL (splitless). The initial column temperature is 50 °C, held for 1 min; heated at a rate of 20 °C·min -1 to 180 °C and held for 5 min, heated at a rate of 20 °C·min -1 to 220 °C and held for 5 min; heated at a rate of 20 °C·min -1 to 260 °C and held for 5 min, heated at a rate of 20 °C·min -1 to 280 °C and held for 5 min. The carrier gas is nitrogen with a flow rate of 1.2 mL·L -1 , and the septum purge is 2 mL·L -1 .

[0040] 3.2 Mass spectrometry conditions

[0041] The transfer line temperature is 280 °C, the ionization energy of the electron impact ionization source (EI) is 70 eV, the ion source temperature is 250 °C, full scan SIM for qualitative analysis, and multiple reaction monitoring (MRM) of the mass spectrometry for quantitative analysis.

[0042] 3.3 Qualitative and quantitative analysis of GC-MS / MS

[0043] Full scan SIM for qualitative analysis and selected ion scan MSI for quantitative analysis (see the table).

[0044] Table 1 Qualitative and quantitative ions for the analysis of PAEs reference substances by GC-MS / MS

[0045]

[0046] Four kinds of PAEs standard substances with different concentration series were prepared for GC-MS / MS chromatographic analysis (the data are shown in the table).

[0047] Table 2 Data of GC-MS / MS analysis of PAEs standard substances

[0048]

[0049] Taking the concentrations of the four kinds of PAEs standard substances as the abscissa and the peak areas as the ordinate, a standard curve was drawn (see the table).

[0050] Table 3 Linear regression equations for GC-MS / MS analysis of PAEs standard substances

[0051]

[0052] 3.4. Determination of actual water samples

[0053] MRM quantitative analysis of PAEs in three kinds of urban sewage water samples (see the table).

[0054] Table 4 Contents of PAEs detected in urban sewage by GC-MS / MS

[0055]

[0056] 3.5. Spiked recovery rate of GC-MS / MS

[0057] A spiked recovery test was carried out by adding standard mixed solutions with three different concentrations to the No. 2 water sample, and the spiked recovery rate of each substance was calculated (see Table 5).

[0058] Table 1 Spiked recovery rates of PAEs detected in urban sewage by GC-MS / MS

[0059]

[0060] The spiked recovery rates were between 65% and 148%, meeting the test requirements.

[0061] 3.6. Precision of GC-MS / MS

[0062] The pretreated No. 3 water sample was spiked and measured 11 times repeatedly. The relative standard deviations of the four kinds of PAEs were between 0.38% and 11.07%, meeting the requirements of the analysis method (see the table).

[0063] Table 6 Precision of GC-MS / MS detection of PAEs in urban sewage

[0064]

[0065] 3.7. Method Detection Limit of GC-MS / MS

[0066] Take the prepared mixed standard solution of 1.00 mg·L -1 and continuously dilute it. Finally, the method detection limits of DEP and DBP are determined to be 0.012 and 0.042 mg·L -1 .

Claims

1. A method for determining plasticizers in urban sewage, characterized in that, It includes the following steps: (1) Take a water sample of urban sewage, filter it successively with filter paper and filter membrane, store it in a refrigerator at 4°C, and complete the pretreatment within 24 hours; (2) Activate and balance the solid-phase extraction column, and perform solid-phase extraction on the water sample; (3) Use a mixed solution of dichloromethane and methanol as the eluent for elution. After the eluate is dried with nitrogen, it is fixed with methanol for determination; (4) Use gas chromatography-mass spectrometry / mass spectrometry to detect the phthalate content in the test solution.

2. The method according to claim 1, wherein In step (1), the pH of the urban sewage water sample is adjusted to about 2.0 before filtration.

3. The method according to claim 1, wherein The solid-phase extraction column is a C18 reversed-phase small column.

4. The method according to claim 1, wherein The solid-phase extraction column in step (2) is activated successively with dichloromethane and methanol.

5. The method according to claim 1, characterized in that, The solid-phase extraction column in step (2) is balanced with ultrapure water.

6. The method according to claim 1, wherein In step (3), the volume ratio of dichloromethane and methanol in the eluent is 7:

3.

7. The method according to claim 1, wherein In step (3), for 0.5 L of water sample, 8 ml of eluent is used.

8. The method according to claim 1, characterized in that, In step (3), the eluent is added to the solid-phase extraction column and allowed to stand for 5 min before elution.

9. The method according to claim 1, characterized in that, In step (4), the chromatographic conditions for gas chromatography-mass spectrometry / mass spectrometry detection are as follows: the chromatographic column is HP-5MS; the inlet temperature is 250°C; the carrier gas is helium; the flow rate is 1.2 mL / min, splitless injection, and the injection volume is 1 μL; The mass spectrometry conditions for gas chromatography-mass spectrometry / mass spectrometry detection are as follows: the ionization mode is electron impact ionization source (EI), the ionization energy is 70 eV, the ion source temperature is 230°C; the transfer line temperature is 280°C; the solvent delay time is 7 min, the mass spectrometry qualitative analysis adopts the full scan (SIM) mode, the scanning range is 50-500 m / z, and the quantitative analysis adopts the multiple reaction monitoring (MRM) mode.

10. The method according to claim 1, characterized in that, In step (4), the programmed temperature rise conditions for gas chromatography-mass spectrometry / mass spectrometry detection are as follows: the initial column temperature is 50°C, held for 1 min, heated to 180°C at a rate of 20°C / min, and held for 5 min; then heated to 220°C at a rate of 20°C / min and held for 5 min; then heated to 260°C at a rate of 20°C / min; held for 5 min; then heated to 280°C at a rate of 20°C / min and held for 5 min.

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