Method for testing content of medium-chain chlorinated paraffin and application

Abstract

The invention provides a method for testing the content of medium-chain chlorinated paraffin and application, a sample is subjected to ultrasonic extraction by an extraction solvent, and the obtained sample solution is subjected to qualitative and quantitative analysis by gas chromatography-triple quadrupole tandem mass spectrometry after being subjected to acid purification treatment. The content of the medium-chain chlorinated paraffin in the sample is calculated according to the following formula: # imgabs0 #, wherein omega is the content of the medium-chain chlorinated paraffin in the sample; a is the peak area of the medium-chain chlorinated paraffin in the to-be-detected liquid; a0 is the peak area of medium-chain chlorinated paraffin in the blank sample; ai is the peak area of medium-chain chlorinated paraffin in the standard working solution; ci is the concentration of medium-chain chlorinated paraffin in the standard working solution; v is the volume of the liquid to be measured; f is a dilution factor of the to-be-detected liquid; m is the mass of the sample.

Description

Technical Field

[0001] The present invention relates to a method for testing the content of medium-chain chlorinated paraffins and its application. Background Art

[0002] Chlorinated paraffins (CPs) are a class of chlorinated derivatives of artificially synthesized straight-chain normal alkanes and are widely used in the metal processing and plastics industries. Chlorinated paraffins are currently the largest-volume persistent anthropogenic synthetic compounds synthesized artificially. Chlorinated paraffins can be divided into short-chain chlorinated paraffins (C 10 ~C 13 , SCCPs), medium-chain chlorinated paraffins (C 14 ~C 17 , MCCPs), and long-chain chlorinated paraffins (C 18 ~C 30 ).

[0003] SCCPs have attracted wide attention due to their persistence, bioaccumulation, and toxicity. In 2017, SCCPs were officially listed in the list of controlled POPs under the Stockholm Convention on Persistent Organic Pollutants (POPs Convention). China is also actively promoting the control of SCCPs. According to the Action Plan for the Control of New Pollutants and the List of Key Controlled New Pollutants (2023 Edition), the production, processing, use, and import and export of 8 types of key controlled new pollutants such as short-chain chlorinated paraffins have been completely phased out. With the continuous strengthening of control efforts, some manufacturers have also started to use MCCPs or LCCPs as substitutes for SCCPs. Currently, MCCPs and LCCPs have also begun to be gradually included in the list of restricted substances by some countries to reduce their potential impact on the environment and health.

[0004] On the other hand, the detection of chlorinated paraffins has the following difficulties:

[0005] 1. Chlorinated paraffins are divided into short-chain chlorinated paraffins (SCCPs), medium-chain chlorinated paraffins (MCCPs), and long-chain chlorinated paraffins (LCCPs). Different types of chlorinated paraffins require different detection methods, which increases the complexity of detection. Currently, many detection methods are for short-chain chlorinated paraffins. The gas chromatography-tandem mass spectrometry method also mainly detects and quantifies short-chain chlorinated paraffins. It is difficult to detect and quantify medium-chain chlorinated paraffins and long-chain chlorinated paraffins.

[0006] 2. The concentration of chlorinated paraffins in environmental and biological samples is usually very low, and high-sensitivity detection techniques are required to accurately detect them.

[0007] 3. Chlorinated paraffins with different chain lengths and their isotope peaks have similar molecular weights and cannot be distinguished by low-resolution mass spectrometry. When analyzing chlorinated paraffins using low-resolution mass spectrometry, there is significant interference and low accuracy.

[0008] 4. The sample matrix is complex, and there is interference from other compounds, affecting the accuracy of the test results.

[0009] Chinese patent document with application number 201610848943.9 provides a method for determining short-chain and medium-chain chlorinated paraffins in consumer products, including the following steps: Step S1, sample pretreatment: Pretreat the sample using ultrasonic extraction to obtain SCCP and MCCP sample solutions; Step S2, use high-performance liquid chromatography-tandem mass spectrometry to effectively ionize SCCP and MCCP in the sample solution into several groups of characteristic ion pairs through atmospheric pressure chemical ionization and collect these characteristic ion pairs; Step S3, prepare standard substance solutions of various chlorinated paraffins, and use high-performance liquid chromatography-tandem mass spectrometry to effectively ionize SCCP and MCCP in the standard substance solutions into multiple groups of characteristic ion pairs through atmospheric pressure chemical ionization and collect these characteristic ion pairs; Step S4, qualitative and quantitative analysis. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a test method for the content of medium-chain chlorinated paraffins that can effectively avoid the interference of short-chain and long-chain chlorinated paraffins, with a simple and efficient test method.

[0011] The technical problem to be solved can be implemented through the following technical solutions.

[0012] A test method for the content of medium-chain chlorinated paraffins, characterized in that the sample is ultrasonically extracted with an extraction solvent, and the obtained sample solution is acid-purified and then qualitatively and quantitatively analyzed by gas chromatography-triple quadrupole tandem mass spectrometry, and the content of medium-chain chlorinated paraffins in the sample is calculated according to the following formula:

[0013]

[0014] In the formula:

[0015] ω is the content of medium-chain chlorinated paraffins in the sample;

[0016] A is the peak area of medium-chain chlorinated paraffins in the liquid to be measured;

[0017] A0 is the peak area of medium-chain chlorinated paraffins in the blank sample;

[0018] A i is the peak area of medium-chain chlorinated paraffins in the standard working solution;

[0019] c i is the concentration of medium-chain chlorinated paraffins in the standard working solution;

[0020] V is the volume of the test solution;

[0021] f is the dilution factor of the test solution;

[0022] m is the mass of the sample.

[0023] Furthermore, it includes the following analysis steps:

[0024] (1) Prepare a standard working solution of medium-chain chlorinated paraffins;

[0025] (2) Ultrasonically extract the sample;

[0026] (3) Add acid to the extract, mix well, and separate with a centrifuge. Collect the upper organic solution; repeat the purification operation until the lower acid solution is clear or white.

[0027] Furthermore, the analysis conditions for gas chromatography-triple quadrupole tandem mass spectrometry are as follows:

[0028] Chromatographic column: DB-5MS; capillary column, 30m × 0.25mm × 0.25μm;

[0029] Injector temperature: 300 °C;

[0030] Column temperature: Programmed temperature rise. After maintaining at 90 °C for 1 min, increase to 150 °C at a rate of 25 °C / min, and then increase to 300 °C at a rate of 8 °C / min and maintain for 6 min;

[0031] Mass spectrometry interface temperature: 280 °C;

[0032] Ion source temperature: 320 °C;

[0033] Mass scanning range: 50 amu to 550 amu;

[0034] Injection mode: Splitless injection;

[0035] Monitoring mode: Selected reaction monitoring;

[0036] Carrier gas: 99.999% helium, with a flow rate of 1.0 mL / min;

[0037] Injection volume: 1.0 μL;

[0038] Solvent delay: 4.0 min.

[0039] Further, during qualitative and quantitative analysis, the standard solution and the sample solution are analyzed according to the analysis conditions suitable for the experimental instrument. Qualitative analysis is carried out based on the retention time of the chromatographic peak and the relative abundance of the characteristic ions. Under the condition of confirming that it is medium-chain chlorinated paraffin, according to the content of the substance to be measured in the sample solution, a mixed standard working solution with a similar concentration is selected. The response values of short-chain chlorinated paraffin in the mixed standard working solution and the sample to be measured should both be within the linear range of the instrument detection. Quantitative analysis is carried out using the characteristic peak of the quantitative ion 129.1 / 93.1.

[0040] Further, when preparing the medium-chain chlorinated paraffin standard working solution, three medium-chain chlorinated paraffin standards with different chlorine contents in the range of 40%-60% are selected. After being fully mixed in a certain proportion, they are prepared into a standard working solution with a suitable concentration using an extraction solvent. Preferably, the medium-chain chlorinated paraffin standard solutions with an average chlorine degree of 42%, 52% and 57% are mixed in a ratio of 1:1:1, and after being fully mixed, they are prepared into a standard working solution with a suitable concentration using an extraction solvent.

[0041] Furthermore, during ultrasonic extraction, 3-6 ml of extraction solution is added per 1 g of sample, and ultrasonic extraction is carried out for more than 60 min at a water temperature of 55-65°C, and then shaken well and cooled. Among them, it is preferred that the ratio of the sample to the extraction solution is 1 g:5 ml. The extraction solvent is added to the sample in a screw-cap graduated test tube with a sealed cap, and ultrasonic extraction is carried out for more than 60 min at a water temperature of 60°C using an ultrasonic generator, and then shaken well and cooled.

[0042] Preferably, the extraction solvent is n-hexane and the acid is concentrated sulfuric acid.

[0043] Further, the reference detection limit of the medium-chain chlorinated paraffin content is 0.1 g / kg

[0044] Another technical problem to be solved by the present invention is to provide an application of the foregoing method in testing the medium-chain chlorinated paraffin content in plastic runway and its raw materials.

[0045] The method for testing the medium-chain chlorinated paraffin content using the above technical scheme has the following characteristics and beneficial effects:

[0046] 1. The detection limit is lower than that of the conventional detection of medium-chain chlorinated paraffin, and can reach 0.05 g / kg;

[0047] 2. Selecting the characteristic peak of the characteristic ions 129.1 / 93.1 for qualitative and quantitative analysis can effectively avoid the interference of short-chain chlorinated paraffin and long-chain chlorinated paraffin;

[0048] 3. The method is simple, efficient and cost-saving. Specific embodiments

[0049] The following further elaborates on the specific implementation manners of the present invention.

[0050] The present invention provides a method for testing the content of medium-chain chlorinated paraffins (C 14 ~C 17 ), which adopts gas chromatography-triple quadrupole tandem mass spectrometry. It can be applied to the testing of the content of medium-chain chlorinated paraffins in plastic runways and their raw materials.

[0051] 1. Principle

[0052] The sample is ultrasonically extracted using n-hexane or other suitable solvents as the extraction solvent. After the obtained sample solution is purified with concentrated sulfuric acid, qualitative and quantitative analysis is carried out by gas chromatography-triple quadrupole tandem mass spectrometry.

[0053] 2. Reagents and materials

[0054] 2.1 Extraction solvent: n-hexane or other suitable solvents, of analytical grade.

[0055] Standard samples of medium-chain chlorinated paraffins with chlorine contents of 42%, 52%, and 57% respectively, with a mass concentration of 100 mg / L. 2.3 Concentrated sulfuric acid: of analytical grade.

[0056] 3. Instruments and equipment

[0057] 3.1 Gas chromatography-mass spectrometry combined instrument: equipped with an electron capture negative chemical ionization source or an electron impact ionization source.

[0058] 3.2 Ultrasonic generator.

[0059] 3.3 Electronic balance: with a precision of 0.1 mg.

[0060] 3.4 Centrifuge: with a rotation speed of 5000 r / min to 20000 r / min.

[0061] 4. Analysis steps

[0062] 4.1 Medium-chain chlorinated paraffin standard working solution

[0063] Mix the medium-chain chlorinated paraffin standard solutions with average chlorination degrees of 42%, 52%, and 57% in a ratio of 1:1:1. After thorough mixing, prepare a standard working solution with a suitable concentration using the extraction solvent.

[0064] 4.2 Ultrasonic extraction

[0065] Weigh approximately 1 g of the sample, accurate to 0.1 mg, and place it in a screw-cap graduated test tube (with a sealed cap). Add 5 mL of the extraction solvent, and ultrasonically extract at a water temperature of 60°C for 60 min using an ultrasonic generator. After shaking and cooling, it is ready for further processing.

[0066] Among them, the high-concentration samples can be subjected to 2 extraction tests. If there are particulate matters in the test solution, take a part of the test solution, filter it through a 0.45μm organic microporous membrane, and use it for detection and analysis.

[0067] 4.3. Purification

[0068] Add 5 mL of 98% concentrated sulfuric acid to the extraction solution, mix well and separate by centrifuge, and collect the upper organic solution. Repeat the above operation until the lower acid solution is clear or white, and this process does not exceed five times.

[0069] Among them, this solution can be directly injected according to the actual situation, or tested after dilution with an extraction solvent. 5. Gas Chromatography-Triple Quadrupole Tandem Mass Spectrometry

[0070] 5.1 Gas Chromatography-Triple Quadrupole Tandem Mass Spectrometry Analysis Conditions

[0071] Since the test results depend on the instrument used, it is impossible to give general parameters for instrumental analysis. The reference instrumental conditions are as follows:

[0072] —— Chromatographic column: DB-5MS capillary column, 30m×0.25mm×0.25μm, or other capillary columns with equivalent properties;

[0073] —— Injection port temperature: 300°C;

[0074] —— Column temperature: Programmed temperature rise. After maintaining at 90°C for 1 min, raise the temperature to 150°C at a rate of 25°C / min, and then raise the temperature to 300°C at a rate of 8°C / min and maintain for 6 min;

[0075] —— Mass spectrometry interface temperature: 280°C;

[0076] —— Ion source temperature: 320°C;

[0077] —— Mass scanning range: 50 amu to 550 amu;

[0078] —— Injection mode: Splitless injection;

[0079] —— Monitoring mode: Selected reaction monitoring (SRM);

[0080] —— Carrier gas: Helium (99.999%), flow rate is 1.0 mL / min;

[0081] —— Injection volume: 1.0 μL;

[0082] —— Solvent delay: 4.0 min.

[0083] 5.2 Test

[0084] Inject 1 μL of the standard working solution and the sample solution into the chromatograph respectively, and operate according to the analysis conditions. Qualitative or quantitative analysis is carried out by comparing the retention times and characteristic ions of the sample and the standard sample.

[0085] 5.3 Qualitative and Quantitative Analysis

[0086] Analyze the standard solution and the sample solution according to the analysis conditions suitable for the instruments in each laboratory, and conduct qualitative analysis based on the retention time of the chromatographic peak and the relative abundance of the characteristic ions. Under the condition of confirming that it is medium-chain chlorinated paraffin (C 14 -C 17 ), select a mixed standard working solution with a concentration similar to that of the sample solution according to the content of the substance to be measured in the sample solution. The response values of short-chain chlorinated paraffin in the mixed standard working solution and the sample to be measured should both be within the linear range of the instrument detection. Quantitative analysis is carried out using the characteristic peak of the quantitative ions 129.1 / 93.1. Refer to Table 1 for the selection of precursor ions, product ions and collision energies for qualitative and quantitative analysis.

[0087] Table 1: Selection of precursor ions, product ions and collision energies for qualitative and quantitative analysis

[0088] Parent ion (m / z) Product ion (m / z) Collision energy eV 79.1 51.0 20 89.0 53.0 10 91.0 65.0 15 91.1 53.0 8 102.0 67.0 10 103.0 75.0 10 115.0 79.0 15 129.1 77.0 18 129.1 91.1 6 129.1 93.1 4

[0089] 6 Blank Test

[0090] Except for not adding the sample, all are carried out according to the above analysis steps.

[0091] 7 Result Calculation

[0092] Calculate the content of medium-chain chlorinated paraffin in the sample according to the following formula:

[0093]

[0094] In the formula:

[0095] ω—the content of medium-chain chlorinated paraffin in the sample, unit: gram per kilogram (g / kg);

[0096] A—the peak area of medium-chain chlorinated paraffin in the liquid to be measured;

[0097] A0—the peak area of medium-chain chlorinated paraffin in the blank sample;

[0098] A i —the peak area of medium-chain chlorinated paraffin in the standard working solution;

[0099] c i —the concentration of medium-chain chlorinated paraffin in the standard working solution, unit: milligram per liter (mg / L);

[0100] V—the volume of the liquid to be measured, unit: milliliter (mL);

[0101] f——Dilution factor of the test solution;

[0102] m——Mass of the sample, unit is gram (g).

[0103] 8. Detection limit

[0104] The reference detection limit of the content of chlorinated paraffins in this method is 0.1 g / kg.

[0105] 9. Precision

[0106] Under the same conditions in the same laboratory, for the same object to be measured within a short period of time, the absolute difference between the two independent determination results should not be greater than 15% of their arithmetic mean.

Claims

1. A test method for the content of medium-chain chlorinated paraffins, characterized in that, The sample was ultrasonically extracted with an extraction solvent. After the obtained test solution was acid-purified, qualitative and quantitative analysis was carried out by gas chromatography-triple quadrupole tandem mass spectrometry, and the content of medium-chain chlorinated paraffins in the test sample was calculated according to the following formula: Where: ω is the content of medium-chain chlorinated paraffins in the test sample; A is the peak area of medium-chain chlorinated paraffins in the liquid to be measured; A0 is the peak area of medium-chain chlorinated paraffins in the blank test sample; A i is the peak area of medium-chain chlorinated paraffins in the standard working solution; c i is the concentration of medium-chain chlorinated paraffins in the standard working solution; V is the volume of the liquid to be measured; f is the dilution factor of the liquid to be measured; m is the mass of the test sample.

2. The test method for the content of medium-chain chlorinated paraffins according to claim 1, characterized in that, It includes the following analysis steps: (1) Prepare a standard working solution of medium-chain chlorinated paraffins; (2) Ultrasonically extract the sample; (3) Add acid to the extract, mix well and separate with a centrifuge, and collect the upper organic solution; repeat the purification operation until the lower acid solution is clear or white.

3. The test method for the content of medium-chain chlorinated paraffins according to claim 1, wherein The gas chromatography-triple quadrupole tandem mass spectrometry analysis conditions are as follows: Chromatographic column: DB-5MS; capillary column, 30m×0.25mm×0.25μm; Injection port temperature: 300°C; Column temperature: Programmed temperature rise, hold at 90°C for 1 min, then rise to 150°C at 25°C / min, and then rise to 300°C at 8°C / min and hold for 6 min; Mass spectrometry interface temperature: 280°C; Ion source temperature: 320°C; Mass scanning range: 50 amu - 550 amu; Injection mode: Splitless injection; Monitoring mode: Selected reaction monitoring; Carrier gas: 99.999% helium, flow rate 1.0 mL / min; Injection volume: 1.0 μL; Solvent delay: 4.0 min.

4. The test method for the content of medium-chain chlorinated paraffins according to claim 1 or 3, characterized in that, During qualitative and quantitative analysis, the standard solution and the test solution were analyzed according to the analysis conditions suitable for the experimental instrument. Qualitative analysis was carried out according to the retention time of the chromatographic peak and the relative abundance of the characteristic ions; under the condition of confirming that it is medium-chain chlorinated paraffins, according to the content of the measured substance in the sample solution, a mixed standard working solution with a similar concentration was selected. The response values of short-chain chlorinated paraffins in the mixed standard working solution and the test sample solution should both be within the linear range of the instrument detection; quantitative analysis was carried out using the characteristic peak of the quantitative ion 129.1 / 93.

1.

5. The method for testing the content of medium-chain chlorinated paraffins according to claim 2, characterized in that, When preparing the standard working solution of medium-chain chlorinated paraffins, three medium-chain chlorinated paraffin standards with different chlorine contents in the range of 40%-60% were selected. After being fully mixed in a certain proportion, they were prepared into a standard working solution with a suitable concentration with an extraction solvent.

6. The test method for the content of medium-chain chlorinated paraffins according to claim 5, characterized in that, When preparing the standard working solution of medium-chain chlorinated paraffins, medium-chain chlorinated paraffin standard solutions with an average chlorination degree of 42%, 52% and 57% were mixed in a ratio of 1:1:1, fully mixed, and then prepared into a standard working solution with a suitable concentration with an extraction solvent.

7. The test method for the content of medium-chain chlorinated paraffins according to claim 2, characterized in that, During ultrasonic extraction, add 3 - 6 ml of extraction solution per 1 g of sample and ultrasonically extract for more than 60 min at a water temperature of 55 - 65°C, shake well and cool.

8. The test method for the content of medium-chain chlorinated paraffins according to claim 1 or 2, characterized in that, The extraction solvent is n-hexane, and the acid is concentrated sulfuric acid.

9. The test method for the content of medium-chain chlorinated paraffins according to claim 1 or 2, characterized in that, The reference detection limit of the medium-chain chlorinated paraffin content is 0.1 g / kg.

10. Application of the test method for the content of medium-chain chlorinated paraffins described in any one of claims 1 - 9 in the test of the content of medium-chain chlorinated paraffins in plastic runways and their raw materials.

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