Method for testing short-chain chlorinated paraffin in water body

Abstract

The invention provides a method for testing short-chain chlorinated paraffin in a water body, which comprises the following steps: adding a recovery rate indicator into an extracted short-chain chlorinated paraffin solution, purifying, concentrating, adding an internal standard substance and normal hexane for constant volume to obtain a short-chain chlorinated paraffin solution to be tested, and the addition amount ratio of the internal standard substance to the recovery rate indicator is 1: (0.05-0.25). Short-chain chlorinated paraffin (SCCPs) is a kind of chlorinated paraffin, and the SCCPs entering the environment can be migrated through air, water, sediments, soil, organisms and the like. In short-chain chlorinated paraffin detection, a one-dimensional gas chromatographic method is generally used for separation, but homologues of short-chain chlorinated paraffin and medium-chain chlorinated paraffin have the same quantitative or qualitative ions, retention time is overlapped, and detection precision is reduced. By setting the concentration ratio of the internal standard substance to the recovery rate indicator and utilizing GC-MS / MS, the mutual influence of the SCCPs, the internal standard substance and the recovery rate indicator in the detection result is reduced to the greatest extent, and more accurate detection of the SCCPs is realized.

Description

Technical Field

[0001] The present invention relates to a method for testing short-chain chlorinated paraffins in water bodies, belonging to the field of detection and extraction. Background Art

[0002] Short-chain chlorinated paraffins (SCCPs) are a type of chlorinated paraffins, which are complex mixtures derived from the chlorination of synthetic alkanes with 10-13 carbon atoms in the carbon chain and are used as plasticizers, metalworking fluids, coatings, sealants, flame retardants, etc. Currently, China is the world's most important producer and exporter of chlorinated paraffins. SCCPs have similar physical and chemical properties to traditional POPs, such as persistence, bioaccumulation and magnification, and biological toxicity, and have low solubility, high octanol-water partition coefficient (K ow ), and high octanol-air partition coefficient (K oa ), etc. SCCPs entering the environment can migrate and transform through air, water, sediment, soil, organisms, etc. Due to their long-distance migration characteristics, SCCPs with different concentrations have been detected in environmental media around the world, and even in the ecosystems of the Arctic and Antarctic. SCCPs have not only been widely detected in the sediments of major rivers in China, but also commonly detected in estuarine and coastal sediments. They have been detected in the sediments of the South China Sea, East China Sea, Bohai Sea and Yellow Sea, coastal waters, bays and estuarine waters, etc. In particular, the SCCPs in the sediments of the Pearl River Estuary can reach up to 6.6×10 3 ng / g. Detecting the concentration of SCCPs in the environment and monitoring the threat of SCCPs in water to the health of organisms in real time is of great significance.

[0003] Most studies use one-dimensional gas chromatography (GC) or two-dimensional GC×GC coupled with electron capture negative ion mass spectrometry (ECNI-MS) or time-of-flight mass spectrometry (TOF-MS) or their variants. In the electron capture negative ion (ECNI) mode, SCCPs mainly produce characteristic ions such as [M-Cl]–, [M-HCl]–, [M+Cl]–, etc. The abundances of these characteristic ions are affected by the carbon chain length, chlorination degree of SCCPs molecules, and the ion source temperature during the detection process.

[0004] To detect SCCPs in the environment, one-dimensional gas chromatography is usually used for separation. Low-resolution mass spectrometry (LRMS) in selected ion monitoring (SIM) mode is widely used as a detector. However, one-dimensional gas chromatography combined with LRMS has drawbacks in separating short-chain and medium-chain chlorinated paraffins because some short-chain and medium-chain chlorinated paraffin homologues have the same quantitative or qualitative ions and overlapping retention times. GC × GC can also be applied to the measurement of chlorinated paraffins. So far, only a few laboratories have used GC × GC combined with microelectron capture detection (ECD) or high-resolution time-of-flight mass spectrometry (HRTOF-MS) to quantify short-chain chlorinated paraffins in environmental samples. Although GC × GC-HRTOF-MS is a powerful tool for analyzing chlorinated paraffins in environmental samples, the high cost and complex maintenance of HRTOF-MS limit its use in most laboratories. In addition, GC has a certain ability to eliminate interference, and quadrupole mass spectrometry (MS) is more convenient to operate and maintain. Currently, national and industrial standards (GB / T 33345-2016, GB / T 40263-2021, SN / T 3814-2014) for the detection of SCCPs in media such as electrical and electronic products, textiles, rubber and plastic products have been issued in China, but they are not applicable to the detection of trace SCCPs in environmental media. For this reason, the present invention provides an analytical method using GC coupled with MS / MS (GC-MS / MS) to determine short-chain chlorinated paraffins. Summary of the Invention

[0005] The present invention provides a method for testing short-chain chlorinated paraffins in water bodies, enabling precise detection of short-chain chlorinated paraffins.

[0006] The present invention provides a method for testing short-chain chlorinated paraffins in water bodies, comprising: Adding a recovery indicator to the extracted short-chain chlorinated paraffins, followed by purification, concentration, adding an internal standard and n-hexane for volume fixation to obtain a short-chain chlorinated paraffin solution to be measured, wherein the addition ratio of the internal standard to the recovery indicator is 1:(0.05 - 0.25).

[0007] Further, the internal standard is hexachlorocyclohexane.

[0008] Further, the recovery indicator is trans-chlordane.

[0009] Further, the addition ratio of the short-chain chlorinated paraffins to the internal standard and the recovery indicator is (5 - 25):1:(0.05 - 0.25).

[0010] Even further, it comprises: Step 1: Add 1 volume of extraction agent to 0.1 - 2 volume parts of the water sample to be tested. The extraction agent is a mixed solution of n - hexane and dichloromethane with a volume ratio of 1:1. Step 2: Ultrasonically centrifuge the mixed liquid and collect the upper - layer organic solution. Step 3: Repeat Steps 1 - 2 two to three times, combine the organic solutions, and concentrate them. Step 4: Put the concentrated liquid obtained in Step 3 into a chromatographic purification column for purification, collect the target liquid, and concentrate it again. Step 5: Add an internal standard and a recovery indicator, and make up the volume with n - hexane to obtain the short - chain chlorinated paraffin solution to be tested. Step 6: Detect the short - chain chlorinated paraffin solution to be tested by gas chromatography - tandem triple - quadrupole mass spectrometry (GC - MS / MS).

[0011] Furthermore, the gas chromatography (GC) parameters for the gas chromatography - tandem triple - quadrupole mass spectrometry (GC - MS / MS) detection in Step 6 specifically include: Injector: Injection volume is 1 μL. Wash the injector with n - hexane, 3 μL before injection and 6 μL after injection; wash the injector with acetone, 3 μL before injection and 6 μL after injection. Injection port: Heater temperature is 260 °C, pressure is 12.93 psi, septum purge flow rate is 3 mL / min, splitless injection, purge volume to the split outlet is 50 mL / min, purge time is 1 min. Oven: Oven temperature starts at 100 °C, equilibration time is 0.5 min, the maximum oven temperature is 325 °C. Temperature - rising program: Initial value is 100 °C, hold for 1 min, then increase the temperature to 280 °C at a rate of 15 °C / min and hold for 10 min, and finally increase the temperature to 300 °C at a rate of 10 °C / min and hold for 10 min. The carrier gas is helium, and the reaction gas is methane.

[0012] Furthermore, the MS / MS parameters for the gas chromatography - tandem triple - quadrupole mass spectrometry detection in Step 6 include: Ion source is chemical ionization source (CI), ion source temperature is 160 °C, use gain factor, time filter is off, automatic baseline subtraction is on, advanced MRM / SIM filter is on, scan type is MS2 SIM, calculated EMV is 1387.8 V, gain is 3 - 8.

[0013] Furthermore, the MS / MS parameters for the gas chromatography - tandem triple - quadrupole mass spectrometry detection in Step 6 also include: Gain factor, the gain factor is set to 5.

[0014] Furthermore, the preparation method of the chromatographic purification column in Step 4 is: In the chromatographic column, 1-3 parts by weight of Florisil, 1-3 parts by weight of neutral silica gel, 3-8 parts by weight of acidic silica gel and 3-8 parts by weight of anhydrous sodium sulfate are filled in sequence from bottom to top, thereby forming a multi-layer silica gel-Florisil composite chromatographic column.

[0015] Furthermore, the elution method of the chromatographic purification column in step 4 is as follows: Pre-rinse the chromatographic column with 1-10 volumes of n-hexane, and discard the effluent; after adding 0.04-0.4 volumes of the concentrated solution obtained in step 3, elute with 3-8 volumes of n-hexane and 5-15 volumes of n-hexane-dichloromethane; Collect the eluate.

[0016] Compared with the prior art, the present invention realizes more accurate detection of SCCPs by setting the concentration ratio of the internal standard and the recovery rate indicator, and utilizing the characteristic that SCCPs, the internal standard and the recovery rate indicator will affect each other in the detection results. Description of the Drawings

[0017] Figure 1 It is the standard curve graph of SCCPs in the embodiment of the present invention; Figure 2 It is the standard curve graph of the recovery rate indicator in the embodiment of the present invention; Figure 3 It is the chromatogram without adding the recovery rate indicator in the embodiment of the present invention (the upper figure is the total ion current (TIC) graph, and the lower figure is the selected ion monitoring (SIM) graph of the internal standard); Figure 4 It is the chromatogram with added recovery rate indicator in the embodiment of the present invention (the upper figure is the total ion current (TIC) graph, and the lower figure is the selected ion monitoring (SIM) graph of the internal standard); Figure 5 It is the GS-MS / MS chromatogram of Example 1 and Comparative Examples 2 and 3 of the present invention (a. Comparative Example 2; b. Comparative Example 3; c. Example 1); Figure 6 It is the GS-MS / MS chromatogram of Example 1 and Comparative Examples 4 and 5 of the present invention (a. Comparative Example 4; b. Comparative Example 5; c. Example 1); Figure 7 It is the GC-ECD chromatogram of Comparative Example 1 of the present invention, and the concentration of SCCPs is 50 μg / mL. Detailed Embodiments

[0018] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0019] The preparation of the chromatographic purification column materials in the embodiments of the present invention is as follows: (1) Preparation of absorbent cotton: Put the absorbent cotton into a clean beaker, immerse it in acetone, dichloromethane, and n-hexane successively for ultrasonic treatment for 15 minutes, air dry it, and place it in a narrow-mouth bottle for standby.

[0020] (2) Neutral silica gel: Weigh a certain mass of silica gel and place it in a container (beaker or 500 mL round-bottom flask), put it into an oven, activate it at 180 °C for 12 hours. After cooling overnight, add 3% (w / w) distilled water while shaking, shake well until there is no caking, and then equilibrate overnight. Finally, add n-hexane to immerse it, and equilibrate overnight for standby.

[0021] (3) Acidic silica gel: Weigh a certain mass of silica gel and place it in a container (beaker or 500 mL round-bottom flask), put it into an oven, activate it at 180 °C for 12 hours. After cooling overnight, add 3% (w / w) distilled water while shaking, shake well until there is no caking, and then equilibrate overnight. Dropwise add AR grade concentrated sulfuric acid (silica gel: sulfuric acid = 56:44, w / w) and shake well (pay attention to venting during this period), shake well until there is no caking, and then equilibrate overnight. Finally, add n-hexane to immerse it, and equilibrate overnight for standby.

[0022] (4) Florisil: Weigh a certain mass of Florisil and place it in a container (beaker or 500 mL round-bottom flask), put it into an oven, activate it at 180 °C for 12 hours. After cooling overnight, add n-hexane to immerse it, and equilibrate overnight for standby.

[0023] To simulate the environment of short-chain chlorinated paraffins in water, the specific method is as follows: In a 50 mL polytetrafluoroethylene bottle, add 5 mL of anaerobic water, a certain amount of SCCPs, the recovery indicator trans-chlordane, and other related substances, extract SCCPs in different batches, and detect the extraction accuracy.

[0024] The GC parameters of the embodiments of the present invention and Comparative Examples 2-4 are set as follows: (1) Front injector: Injection volume is 1 μL, solvent A (n-hexane) is used to clean 3 μL before injection and 6 μL after injection; solvent B (acetone) is used to clean 3 μL before injection and 6 μL after injection; (2) Injection port: Heater temperature is 260 °C, pressure is 12.93 psi, septum purge flow rate is 3 mL / min, splitless injection, purge volume to the split outlet is 50 mL / min, purge time is 1 minute; (3) Column oven: Column oven temperature is initially 100 °C, equilibrium time is 0.5 minute, the highest column oven temperature is 325 °C, temperature programming: initial value is 100 °C, hold for 1 minute, then increase the temperature to 280 °C at a rate of 15 °C / min, hold for 10 minutes, and finally increase the temperature to 300 °C at a rate of 10 °C / min, hold for 10 minutes.

[0025] The MS / MS parameter settings for the examples and Comparative Examples 2, 3, and 5 of the present invention are as follows: Ion source: CI, ion source temperature: 160 °C, using gain factor, time filter off, automatic baseline subtraction on, advanced MRM / SIM filter on, scan type: MS2 SIM, calculated EMV: 1387.8 V, gain: 5, number of qualitative ions: 19. Example 1

[0026] The short-chain chlorinated paraffin test method for Example 1 of the present invention is as follows: Step 1: Prepare standard solutions, including: the total concentration of short-chain chlorinated paraffins is 100 μg / mL, and then using n-hexane as the solvent, prepare standard working solutions with total concentrations of short-chain chlorinated paraffins of 2 μg / mL, 4 μg / mL, 6 μg / mL, 8 μg / mL, and 10 μg / mL respectively. Add the recovery indicator trans-chlordane and the internal standard hexachlorocyclohexane. In the standard working solutions, the ratio of the total concentration of short-chain chlorinated paraffins (SCCPs) to the total concentrations of the internal standard and the recovery indicator is 200:10:1; Step 2: Take the water sample to be tested, add 10 mL of a 1:1 mixed solution of n-hexane and dichloromethane. First, fully mix the solution with a vortex mixer, collect the upper organic solution after ultrasonic centrifugation, and repeat the extraction three times; Place the collected extract in a pear-shaped flask and concentrate it to about 2 mL by rotary evaporation; Step 3: Plug the lower end of a chromatography column with an inner diameter of 1 cm with degreased cotton (ultrasonicated with acetone, dichloromethane, and n-hexane for 15 minutes each and then dried for standby), and sequentially pack 3 g of Florisil, 2 g of neutral silica gel, 5 g of acidic silica gel, and 4 g of anhydrous sodium sulfate from bottom to top to form a multi-layer silica-Florisil composite chromatography column; Pre-rinse the chromatography column with 50 mL of n-hexane and discard the effluent; After adding 2 mL of the concentrated extract, elute with 40 mL of n-hexane and 100 mL of n-hexane-dichloromethane (1:1, V / V); Collect the eluents of the two parts in a 250 mL pear-shaped flask, concentrate to about 1.5 mL, and blow to near dry with nitrogen. Add 20 μL of the internal standard hexachlorocyclohexane with a concentration of 10 μg / mL and 20 μL of the recovery indicator trans-chlordane with a concentration of 10 μg / mL; Make up the volume with n-hexane. The concentration of the internal standard after volume making is the same as that of the internal standard in the standard curve, and the concentration of the recovery indicator is the same as the middle concentration of the recovery indicator standard curve.

[0027] Step 4: GS-MS / MS detection. The qualitative ion parameters of each compound in the example of the present invention are shown in the following table.

[0028]

[0029] Comparative Example 1

[0030] The standard sample of SCCPs mixed standard was determined by the method of gas chromatography - electron capture detector (GC-ECD) combined. The chromatographic column used was HP-5MS, with a specification of 30m×0.25mm×0.25μm. The carrier gas was high-purity nitrogen (N2, 99.999%), the flow rate was 4mL / min, the detector temperature was 310℃, and the injection port temperature was 270℃.

[0031] The chromatographic column temperature programming was set as follows: hold at 90℃ for 1 min, increase to 150℃ at a rate of 20℃ / min, then increase the temperature to 300℃ at a rate of 15℃ / min, and hold for 4 min.

[0032] The injection volume was 1μL, splitless injection, and the valve was opened after 1 min. The standard curves with concentrations of 10, 20, 30, 40, 50, 80, and 100 μg / mL were fitted, and R 2 = 0.998.

[0033] For Comparative Example 1 of the present invention, R 2 = 0.998 although it meets the requirements, there are obvious problems. On the one hand, from a practical sense, such high concentrations of SCCPs generally do not appear in actual environmental media. Therefore, the comparative example is actually not applicable to environmental detection and has strong limitations. On the contrary, as Figure 3 and Figure 7 show, the applicable detection range of Example 1 of the present invention is one order of magnitude lower than that of Comparative Example 1, which is more in line with the needs of environmental detection. On the other hand, as Figure 1 shows, the fitting effect of Comparative Example 1 of the present invention is not as high as that of Example 1 of the present invention. Therefore, the sample measurement method of the present invention is more accurate for the quantification of SCCPs.

[0034] Comparative Example 2

[0035] The test method for short-chain chlorinated paraffins in Comparative Example 2 of the present invention is as follows: Step 1: Prepare the standard solution, including: the total concentration of short-chain chlorinated paraffins was 100 μg / mL, and then using n-hexane as the solvent, standard working solutions with total concentrations of short-chain chlorinated paraffins of 2μg / mL, 4μg / mL, 6μg / mL, 8μg / mL, and 10μg / mL were respectively prepared, and the recovery indicator trans-chlordane and the internal standard hexachlorocyclohexane were respectively added, so that the ratio of the total concentration of short-chain chlorinated paraffins (SCCPs) to the total concentration of the internal standard and the recovery indicator in the standard working solution was 20:2:10; Step 2: Add 10 mL of a 1:1 mixed solution of n-hexane and dichloromethane to each sample to be tested. First, use a vortex machine to fully mix the solution. After ultrasonic centrifugation, collect the upper organic liquid, and repeat the extraction three times; place the collected extraction liquid in a pear-shaped flask and concentrate it to about 2 mL; Step 3: Plug the lower end of a chromatography column with an inner diameter of 1 cm with degreased cotton (ultrasonicated with acetone, dichloromethane, and n-hexane for 15 min each and then dried for standby), and sequentially pack 3 g of Florisil, 2 g of neutral silica gel, 5 g of acidic silica gel, and 4 g of anhydrous sodium sulfate from bottom to top to form a multi-layer silica-Florisil composite chromatography column; pre-rinse the chromatography column with 50 mL of n-hexane and discard the eluate; after adding 2 mL of the concentrated extract, elute with 40 mL of n-hexane and 100 mL of n-hexane-dichloromethane (1:1, V / V); collect the eluates of the two parts in a 250 mL pear-shaped flask, concentrate to about 1.5 mL, and blow to near dryness with nitrogen, add 20 μL of internal standard hexachlorocyclohexane with a concentration of 10 μg / mL and 20 μL of recovery indicator trans-chlordane with a concentration of 10 μg / mL; make up the volume with n-hexane so that the concentration of the internal standard in the final solution is the same as that in the standard curve, and the concentration of the recovery indicator is the same as the middle concentration of the recovery indicator standard curve. Perform GS-MS / MS detection on the machine.

[0036] Comparative Example 3

[0037] The test method for short-chain chlorinated paraffins in Comparative Example 3 of the present invention is as follows: Step 1: Prepare standard solutions, including: the total concentration of short-chain chlorinated paraffins is 100 μg / mL, and then using n-hexane as the solvent, prepare standard working solutions with total concentrations of short-chain chlorinated paraffins of 2 μg / mL, 4 μg / mL, 6 μg / mL, 8 μg / mL, and 10 μg / mL respectively, and add the recovery indicator trans-chlordane and the internal standard hexachlorocyclohexane respectively, so that in the standard working solutions, the ratio of the total concentration of short-chain chlorinated paraffins (SCCPs) to the total concentrations of the internal standard and the recovery indicator is 20:2:1; Step 2: Add 10 mL of a 1:1 mixture of n-hexane and dichloromethane to each sample to be tested, first mix the solution thoroughly with a vortex mixer, collect the upper organic layer after ultrasonic centrifugation, and repeat the extraction three times; place the collected extract in a pear-shaped flask and concentrate to about 2 mL; Step 3: Plug the lower end of a chromatographic column with an inner diameter of 1 cm with degreased cotton (ultrasonicated with acetone, dichloromethane, and n - hexane for 15 min respectively and then air - dried for standby), and sequentially pack 3 g of Florisil, 2 g of neutral silica gel, 5 g of acidic silica gel, and 4 g of anhydrous sodium sulfate from bottom to top to form a multi - layer silica gel - Florisil composite chromatographic column; pre - rinse the chromatographic column with 50 mL of n - hexane, discard the eluate; after adding 2 mL of the concentrated extract, elute with 40 mL of n - hexane and 100 mL of n - hexane - dichloromethane (1:1, V / V); collect the eluates of two parts in a 250 - mL pear - shaped flask, concentrate to about 1.5 mL, and blow to near - dry with nitrogen. Add 20 μL of internal standard hexachlorocyclohexane with a concentration of 10 μg / mL and 20 μL of recovery indicator trans - chlordane with a concentration of 10 μg / mL; make the volume constant with n - hexane. The concentration of the internal standard after volume - constant is the same as that of the internal standard in the standard curve, and the concentration of the recovery indicator is the same as the middle concentration of the recovery indicator standard curve. Perform GS - MS / MS detection on the machine.

[0038] Preparation method of silica gel - Florisil chromatographic column: Step 1: (1) Put the degreased cotton into a clean beaker, immerse it in acetone, dichloromethane, and n - hexane successively for ultrasonic treatment for 15 min, air - dry and place it in a narrow - mouth bottle for standby; (2) Florisil: Put Florisil into a round - bottom flask, activate it in an oven at 180 °C for 12 h, and wait until it cools completely. Add n - hexane to immerse it, and let it equilibrate overnight for standby; (3) Neutral silica gel: Activate the silica gel in an oven at 180 °C for 12 h. After it cools completely, add ultrapure water with a mass fraction of 3% (w / w) while shaking, shake well until there is no caking, then equilibrate for 12 h, and then add n - hexane to immerse it, and equilibrate for standby; (4) Acidic silica gel: Weigh a certain mass of silica gel and place it in a round - bottom flask, activate it in an oven at 180 °C for 12 h. After it cools completely, add 3% distilled water in portions, shake well until there is no caking, and then equilibrate overnight. Dropwise add concentrated sulfuric acid (silica gel: sulfuric acid = 56:44, w / w), shake well and pay attention to releasing gas during shaking. After shaking well until there is no caking, equilibrate overnight, add n - hexane to immerse it, and equilibrate overnight; (5) Anhydrous sodium sulfate: Put anhydrous sodium sulfate into a round - bottom flask, activate it in an oven at 180 °C for 12 h, and wait until it cools completely for standby.

[0039] Step 2: Fill the bottom of a 1 - cm - inner - diameter glass chromatographic column equipped with a polytetrafluoroethylene valve with an appropriate amount of degreased cotton, and sequentially pack 3 g of Florisil, 2 g of neutral silica gel, 5 g of acidic silica gel, and 4 g of anhydrous sodium sulfate from bottom to top to form a silica gel - Florisil chromatographic column.

[0040] Comparative Example 4

[0041] The test method for short - chain chlorinated paraffins in Comparative Example 4 of the present invention is as follows: Step 1: Prepare standard solutions, including: the total concentration of short-chain chlorinated paraffins is 100 μg / mL. Then, using n-hexane as the solvent, prepare standard working solutions with total short-chain chlorinated paraffin concentrations of 2 μg / mL, 4 μg / mL, 6 μg / mL, 8 μg / mL, and 10 μg / mL respectively. Add the recovery indicator trans-chlordane and the internal standard hexachlorocyclohexane. In the standard working solutions, the ratio of the total concentration of short-chain chlorinated paraffins (SCCPs) to the total concentrations of the internal standard and the recovery indicator is 200:10:1; Step 2: Take 10 mL of the standard working solution from each vial selected in each batch, add 10 mL of a 1:1 mixture of n-hexane and dichloromethane. First, thoroughly mix the solution with a vortex mixer, collect the upper organic layer after ultrasonic centrifugation, and repeat the extraction three times; Place the collected extract in a pear-shaped flask and concentrate it to about 2 mL; Step 3: Plug the lower end of a chromatography column with an inner diameter of 1 cm with degreased cotton (ultrasonicated with acetone, dichloromethane, and n-hexane for 15 minutes each and then dried for standby), and sequentially pack 3 g of Florisil, 2 g of neutral silica gel, 5 g of acidic silica gel, and 4 g of anhydrous sodium sulfate from bottom to top to form a multi-layer silica-Florisil composite chromatography column; Pre-rinse the chromatography column with 50 mL of n-hexane and discard the effluent; After adding 2 mL of the concentrated extract, elute with 40 mL of n-hexane and 100 mL of n-hexane-dichloromethane (1:1, V / V); Collect the eluents from the two parts in a 250 mL pear-shaped flask, concentrate to about 1.5 mL, and blow to near dry with nitrogen. Add 20 μL of the internal standard hexachlorocyclohexane with a concentration of 10 μg / mL and 20 μL of the recovery indicator trans-chlordane with a concentration of 10 μg / mL; Make up the volume with n-hexane. The concentration of the internal standard after volume making is the same as that of the internal standard in the standard curve, and the concentration of the recovery indicator is the same as the middle concentration of the recovery indicator standard curve. Perform GS-MS / MS detection on the machine.

[0042] The GC parameters for the comparative example of the present invention are set as follows: (1) Front injector: Injection volume is 1 μL. Solvent A (n-hexane) is used to clean 3 μL before injection and 6 μL after injection; Solvent B (acetone) is used to clean 3 μL before injection and 6 μL after injection; (2) Injection port: Heater at 260 °C, pressure 12.93 psi, septum purge flow rate 3 mL / min, splitless injection, purge volume to the split outlet 50 mL / min, purge time 1 min; (3) Column temperature conditions of the national standard (GB / T 40263-2021): Temperature programming, initial value 90 °C, hold for 1 min, then increase the temperature to 150 °C at a rate of 25 °C / min, and finally increase the temperature to 300 °C at a rate of 8 °C / min, hold for 15 min.

[0043] Comparative Example 5

[0044] The test method for short-chain chlorinated paraffins in Comparative Example 5 of the present invention is as follows: Step 1: Prepare standard solutions, including: the total concentration of short-chain chlorinated paraffins is 100 μg / mL, and then using n-hexane as a solvent, prepare standard working solutions with total concentrations of short-chain chlorinated paraffins of 2 μg / mL, 4 μg / mL, 6 μg / mL, 8 μg / mL, and 10 μg / mL respectively. Add the recovery indicator trans-chlordane and the internal standard hexachlorocyclohexane, so that in each solution, the ratio of the total concentration of short-chain chlorinated paraffins (SCCPs) to the total concentrations of the internal standard and the recovery indicator is 200:10:1; Step 2: Add 10 mL of a 1:1 mixed solution of n-hexane and dichloromethane to each sample to be tested. First, use a vortex mixer to fully mix the solution, and after ultrasonic centrifugation, collect the upper organic liquid. Repeat the extraction three times; place the collected extraction solution in a pear-shaped flask and concentrate it to about 2 mL; Step 3: Plug the lower end of a chromatographic column with an inner diameter of 1 cm with degreased cotton (ultrasonicated with acetone, dichloromethane, and n-hexane for 15 minutes each and then dried for standby), and sequentially pack 3 g of Florisil, 2 g of neutral silica gel, 5 g of acidic silica gel, and 4 g of anhydrous sodium sulfate from bottom to top to form a multi-layer silica-Florisil composite chromatographic column; pre-rinse the chromatographic column with 50 mL of n-hexane and discard the effluent; after adding 2 mL of the concentrated extraction solution, elute with 40 mL of n-hexane and 100 mL of n-hexane-dichloromethane (1:1, V / V); collect the eluents from the two parts in a 250 mL pear-shaped flask, concentrate to about 1.5 mL, and blow to near dry with nitrogen. Add 20 μL of internal standard hexachlorocyclohexane with a concentration of 10 μg / mL and 20 μL of recovery indicator trans-chlordane with a concentration of 10 μg / mL; make up the volume with n-hexane. The concentration of the internal standard after volume making is the same as that of the internal standard in the standard curve, and the concentration of the recovery indicator is the same as the middle concentration of the recovery indicator standard curve. Perform GS-MS / MS detection on the machine.

[0045] The GC parameters setting for the comparative example of the present invention is as follows: (1) Front injector: injection volume 1 μL, wash the injector with solvent A (n-hexane) for 3 μL before injection and 6 μL after injection; wash the injector with solvent B (acetone) for 3 μL before injection and 6 μL after injection; (2) Injection port: heater 260 °C, pressure 12.93 psi, septum purge flow rate 3 mL / min, splitless injection, purge volume to the split outlet 50 mL / min, purge time 1 min; (3) Column oven: the column oven temperature is started at 90 °C, equilibrium time 1 min, the highest column oven temperature 325 °C, temperature programming, initial value 90 °C, hold for 1 min, increase the temperature to 150 °C at a rate of 20 °C / min, and then increase the temperature to 300 °C at a rate of 15 °C / min, hold for 4 min.

[0046] During the SCCPs measurement process, it was found that SCCPs, internal standards, and recovery rate indicators would affect each other in the test results. For example Figure 3 , Figure 4 As shown. In addition, samples with an initial total short-chain chlorinated paraffin concentration of 4 μg / mL in Example 1, Comparative Example 2, and Comparative Example 3, and processed through steps 1-3 were subjected to GS-MS / MS detection. The results are as shown in Figure 5 , Figure 5 where a is the result diagram of Comparative Example 2, b is the result diagram of Comparative Example 3, and c is the result diagram of Example 1. The main difference between Example 1 and Comparative Example 2 and Comparative Example 3 lies in the addition amount of the recovery rate indicator. In Comparative Example 2, the addition amount of the recovery rate indicator was too much, resulting in the SCCPs peak in the spectrum being masked. In Comparative Example 3, the ratio of the total concentration of short-chain chlorinated paraffins (SCCPs) to the total concentration of internal standards and recovery rate indicators was 20:2:1. Although the SCCPs peak could be seen, the peak intensity was lower than 50000. In Example 1, the addition amount of the recovery rate indicator was less, but the SCCPs peak intensity was much higher than that of Comparative Example 2 and Comparative Example 3, reaching up to 10000 at most. When the concentrations of SCCPs and internal standards were the same, the ratio of the peak area of SCCPs without adding the recovery rate indicator to the peak area of the internal standard was 116.7, and the ratio of the peak area of SCCPs with the added recovery rate indicator to the peak area of the internal standard was 99.9. To more accurately detect SCCPs, in Example 1 of the present invention, the optimal concentration ratio (5-25):1:(0.05-0.25) was determined in the combination of SCCPs, internal standards, and recovery rate indicators. The results are as shown in Figure 1 , Figure 2 . The standard curves R 2 of SCCPs and the recovery rate indicator were 0.9996 and 0.9998 respectively. The experimental recovery rate results were between 90% and 115%. A relatively satisfactory recovery rate standard curve and experimental recovery rate were obtained. It should be noted that the optimal concentration ratio determined in the combination of SCCPs, internal standards, and recovery rate indicators was 1:0.1:0.01. However, for a solution with an undetermined specific SCCPs content, as long as the concentration ratio of SCCPs, internal standards, and recovery rate indicators is controlled at (0.5-2):0.1:0.01, good test results can also be obtained.

[0047] In addition, Example 1 of the present invention further optimizes the parameter settings of GC-MS / MS during the sample measurement process. During the sample measurement process, the gain factor is adjusted to 5, and at the same time, the collision gas N2 is turned off to reduce the excessive bombardment of molecules during the GC-MS / MS detection, and a relatively satisfactory recovery rate is obtained in the results. The specific test process is as follows: Samples with an initial total concentration of short-chain chlorinated paraffins of 4 μg / mL in Example 1, Comparative Example 4, and Comparative Example 5, and processed through steps 1-3 are taken for GS-MS / MS detection. The results are as Figure 6 shown, Figure 6 where a is the result graph of Comparative Example 4, b is the result graph of Comparative Example 5, and c is the result graph of Example 1. Figure 6 The SCCPs peak in c is significantly higher than that in Comparative Example 4 and Comparative Example 5. It can be seen that compared with the conventional column temperature conditions of Comparative Example 4 (national standard column temperature) and 5, Example 1 of the present invention can more effectively achieve the separation of SCCPs, and the SCCPs peak intensity in Example 1 of the present invention is obvious. Compared with Comparative Examples 4 and 5, it can perform efficient content testing of SCCPs in water samples.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that after reading the specification of this application, they can still modify the specific implementation manners of the present invention or make equivalent replacements. However, these modifications or changes do not depart from the protection scope of the pending claims of this invention application.

Claims

1. A method for testing short-chain chlorinated paraffins in water, characterized in that, Comprising: Adding a recovery indicator to the extracted short-chain chlorinated paraffins, purifying and concentrating them, then adding an internal standard and n-hexane for volume fixation to obtain a short-chain chlorinated paraffin solution to be measured, and the addition ratio of the internal standard to the recovery indicator is 1:(0.05 - 0.25).

2. The method for testing short-chain chlorinated paraffins in water according to claim 1, characterized in that, The internal standard is hexachlorocyclohexane.

3. The method for testing short-chain chlorinated paraffins in water according to claim 1, wherein The recovery indicator is trans-chlordane.

4. The method for testing short-chain chlorinated paraffins in water according to claim 1, characterized in that, The addition ratio of the short-chain chlorinated paraffins to the internal standard and the recovery indicator is (5 - 25):1:(0.05 - 0.25).

5. The method for testing short-chain chlorinated paraffins in water according to claim 1, characterized in that, Comprising: Step 1: Adding 1 volume part of an extraction agent to 0.1 - 2 volume parts of a water sample to be measured, and the extraction agent is a mixed solution of n-hexane and dichloromethane with a volume ratio of 1:1; Step 2: Ultrasonically centrifuging the mixed liquid and collecting the upper organic solution; Step 3: Repeating Steps 1 - 2 two to three times, combining the organic solutions and concentrating; Step 4: Putting the concentrated solution obtained in Step 3 into a chromatographic purification column for purification, collecting the target liquid, and concentrating again; Step 5: Adding an internal standard and a recovery indicator, and fixing the volume with n-hexane to obtain a short-chain chlorinated paraffin solution to be measured; Step 6: Performing gas chromatography tandem triple quadrupole mass spectrometry detection on the short-chain chlorinated paraffin solution to be measured.

6. The method for testing short-chain chlorinated paraffins in water according to claim 5, wherein The gas chromatography parameters for the gas chromatography tandem triple quadrupole mass spectrometry detection in Step 6 specifically include: Front injector: injection volume 1 μL, cleaning with n-hexane 3 μL before injection and 6 μL after injection; cleaning with acetone 3 μL before injection and 6 μL after injection; Injection port: heater 260 °C, pressure 12.93 psi, septum purge flow rate 3 mL / min, splitless injection, purge volume to the split outlet 50 mL / min, purge time 1 min; Column oven: column oven temperature starts at 100 °C, equilibrium time 0.5 min, maximum column oven temperature 325 °C; temperature programming, initial value 100 °C, hold for 1 min, then increase the temperature to 280 °C at a rate of 15 °C / min, hold for 10 min, and finally increase the temperature to 300 °C at a rate of 10 °C / min, hold for 10 min. The carrier gas is helium and the reaction gas is methane.

7. The method for testing short-chain chlorinated paraffins in water according to claim 5, characterized in that, The MS / MS parameters for the gas chromatography tandem triple quadrupole mass spectrometry detection in Step 6 include: The ion source is a chemical ionization source (CI), the ion source temperature is 160 °C, using a gain factor, the time filter is closed, automatic baseline subtraction is turned on, the advanced MRM / SIM filter is turned on, the scan type is MS2 SIM, the calculated EMV is 1387.8 V, and the gain is 3 - 8.

8. The method for testing short-chain chlorinated paraffins in water according to claim 7, characterized in that, The MS / MS parameters for the gas chromatography tandem triple quadrupole mass spectrometry detection in Step 6 also include: Gain factor, and the gain factor is set to 5.

9. The method for testing short-chain chlorinated paraffins in water according to claim 5, characterized in that, The preparation method of the chromatographic purification column in Step 4 is: Sequentially packing 1 - 3 parts by weight of Florisil, 1 - 3 parts by weight of neutral silica gel, 3 - 8 parts by weight of acidic silica gel, and 3 - 8 parts by weight of anhydrous sodium sulfate from bottom to top in the chromatographic column to form a multi-layer silica-Florisil composite chromatographic column.

10. The method for testing short-chain chlorinated paraffins in water according to claim 5, characterized in that, The elution method of the chromatographic purification column in Step 4 is: Pre-rinse the chromatography column with 1 - 10 volume parts of n-hexane and discard the eluate; after adding 0.04 - 0.4 volume parts of the concentrated solution obtained in Step 3, elute with 3 - 8 volume parts of n-hexane and 5 - 15 volume parts of n-hexane-dichloromethane; Collect the eluate.

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