Method for determining short-chain chlorinated paraffin in rubber

Abstract

The invention relates to determination of short-chain chlorinated paraffin in rubber. The determination comprises the following steps: (1) preparing a sample; (2) purifying; (3) performing gas chromatography-mass spectrometry test; (4) drawing a standard curve; (5) sample testing; (6) qualitatively judging the sample; and (7) quantitatively calculating a result of the sample. The quantitative method for detecting the content of the short-chain chlorinated paraffin in the rubber product through gas chromatography-mass spectrometry is optimized, and the detection accuracy of the short-chain chlorinated paraffin is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of rubber harmful substance detection and relates to a method for determining short-chain chlorinated paraffin in rubber. Background Art

[0002] Short-chain chlorinated paraffins are industrial products of straight-chain chlorinated alkanes with a chain length of 10-13 carbon atoms, and have many homologues. Short-chain chlorinated paraffins are chemically stable, have the ability to migrate over long distances and bioaccumulate, and have been detected in the atmosphere, water bodies, biomes, and human food and tissues. Short-chain chlorinated paraffins have the potential to cause cancer and have attracted the attention of the World Health Organization and environmental researchers. Short-chain chlorinated paraffins are used as flame retardants in rubber.

[0003] At present, the detection methods for short-chain chlorinated paraffins include gas chromatography-mass spectrometry, including GC-ECNI-MS, GC-HRMS, GC-EI-MS 2 Etc. In addition, ECD, FID, etc. are also used as detectors for quantitative analysis of chlorinated paraffins. Countless homologues and isomers are produced during the production of chlorinated paraffins. Current quantitative analysis methods cannot separate, identify, and measure each monomer one by one. The selection of standard samples for quantification is controversial. The distribution of chlorinated paraffins in real samples is complex and it is impossible to select standards with the same monomer distribution as the sample, resulting in large errors in the test. Therefore, it is of great significance to develop a method for detecting short-chain chlorinated paraffins in rubber products with accurate test results. Summary of the invention

[0004] The purpose of the present invention is to invent a method for determining short-chain chlorinated paraffin in rubber, which solves the problems in the prior art of complex distribution of chlorinated paraffin in samples and large errors in the results of testing short-chain chlorinated paraffin.

[0005] The present invention adopts the following technical solutions:

[0006] A method for determining short-chain chlorinated paraffins in rubber has the following steps:

[0007] (1) Sample preparation: Cut the sample into small particles smaller than 1 cm × 1 cm × 1 cm. Weigh 0.5 g of the sample and put it into a screw-type scale container (with a sealing cover). Add 10 ml of n-hexane and use an ultrasonic generator to perform ultrasonic extraction at 60 °C for 60 min. Shake well and cool for later processing.

[0008] (2) Purification: Take 5 ml of the sample solution into a glass tube and add 5 ml of 98% concentrated sulfuric acid, mix well and use a centrifuge to separate, collect the upper organic solution. Repeat the above operation 1 to 3 times until the lower acid solution is clear or white.

[0009] (3) GC-NCI-MS test conditions: chromatographic column: DB-5MS capillary column, 30 m×0.25 mm×0.1 μm; injection port temperature: 300°C; ion source temperature: 200°C; reaction gas: methane.

[0010] (4) Qualitative and quantitative analysis methods:

[0011] Qualitative method: Select a short-chain chlorinated paraffin standard solution with a chlorine content of 59.55% and repeat the measurement, record the peak time of 24 monomers, the relative abundance and peak shape of characteristic ions. Perform qualitative analysis based on the chromatographic peak retention time, the relative abundance and peak shape of characteristic ions between monomers.

[0012] Quantitative method: Select short-chain chlorinated paraffin standard solutions with a concentration of 10 mg / L and chlorine contents of 51.5%, 52.3%, 55.5%, 59.55%, and 63.0%. Repeat the test three times according to the test conditions of GC-NCI-MS. Short-chain chlorinated paraffins are short-chain alkanes of C10-C13, Cl5-Cl10, and have 24 monomers. Add the peak areas of the 24 monomers, and the total peak area and concentration ratio to obtain the total response factor. Establish a standard curve of chlorine content and total response factor, and the regression equation of the standard curve is y=44963.4257x-2, 259902.6728, R=0.997.

[0013] (5) Sample testing: Measure the sample according to the above steps to obtain the total ion current diagram of the sample.

[0014] Calculate the total peak area of ​​short-chain chlorinated paraffins = ∑i monomer peak area, i = 24 short-chain chlorinated paraffin monomers.

[0015]

[0016] Substitute the calculated sample chlorine content into the regression equation to obtain the total response factor of the sample.

[0017]

[0018] The invention provides a method for determining short-chain chlorinated paraffin in rubber. The method comprises the following steps: extracting with concentrated sulfuric acid for purification and testing with GC-NCI-MS, and calculating the content of the short-chain chlorinated paraffin by a response factor correction method. The method can analyze the monomer composition of the chlorinated paraffin, and the calculation result is not affected by the type of chlorinated paraffin used, and the result has high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a standard curve graph;

[0020] Figure 2 This is the total ion current of a standard solution of short-chain chlorinated paraffins. DETAILED DESCRIPTION

[0021] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] The instruments and equipment used in the following examples mainly include PerkinElmer Clarus 690-SQ8C gas chromatograph-mass spectrometer; KH-50A ultrasonic cleaner from Kunshan Hechuang Ultrasonic Instrument Company; and TDL-44 centrifuge from Baochuang Co., Ltd.

[0023] Reagents used: n-hexane, chromatographic grade. Concentrated sulfuric acid, analytical grade. Standard stock solution of short-chain chlorinated paraffin (C10-C13): 51.5% average chlorination, 100 mg / L, 55.5% average chlorination, 100 mg / L, 63.0% average chlorination, 100 mg / L.

[0024] Sample extraction: Cut the sample into small particles less than 1 cm, weigh 0.5 g of sample, accurate to 0.1 mg, put it into a screw-mouth scale container (with a sealed cover), add 10 ml of extraction solvent, use an ultrasonic generator to perform ultrasonic extraction at 60°C water temperature for 60 minutes, shake well, cool and wait for processing.

[0025] Purification: Take 5 ml of sample solution into a glass tube, add 5 ml of 98% concentrated sulfuric acid, mix well and use centrifuge to separate, collect the upper organic solution. Repeat the above operation until the lower acid solution is clear.

[0026] Gas chromatography-mass spectrometry analysis conditions:

[0027] Chromatographic column: DB-5MS capillary column, 30m×0.25mm×0.1μm, injection port temperature: 300℃; column temperature program, 100℃ to 300℃ at 20℃ / min, hold for 5min; mass spectrometer interface temperature: 280℃; ion source temperature: 200℃; injection mode: splitless injection; mass scanning range: 50amu~550amu; ionization mode: electron capture negative chemical source ionization; carrier gas: helium, purity greater than or equal to 99.999%; reaction gas: methane; reaction gas flow rate: 2.0mL / min; solvent delay: 5min;

[0028] Table 1 Short-chain chlorinated paraffin chlorine content 59.55% (C 10 -C 13 ) of the qualitative ion, quantitative ion, qualitative ion quantitative ion ratio, and peak time

[0029]

[0030]

[0031] Qualitative analysis: Select a standard solution of 10 mg / L short-chain chlorinated paraffin with a chlorine content of 59.55% and a concentration of 30 mg / L and inject it three times to obtain a total ion flow chart. Record the retention time and the ratio of qualitative ions to quantitative ions of each monomer in the selected ion mode. Perform qualitative judgment and analysis based on the retention time, the ratio of qualitative ions to quantitative ions, and the shape of the chromatographic peak.

[0032] Quantitative analysis: Mix the standard solutions with chlorine contents of 51.5%, 55.5% and 63.0% to produce short-chain chlorinated paraffin standard solutions with chlorine contents of 52.3% and 59.55%. Dilute each short-chain chlorinated paraffin standard solution to a concentration of 10 mg / L, inject the five short-chain chlorinated paraffin standard solutions with different chlorine contents three times, and establish a standard curve of chlorine content and total response factor. The standard curve y=44963.4257x-2, 259902.6728, R=0.997 has good linearity, and the method detection limit is 0.1 mg / kg.

[0033] Determination of recovery rate and precision: Purchase a short-chain chlorinated paraffin sample with unknown chlorine content and prepare a 62.44 mg / kg liquid sample. Add 500 mg / kg, 1000 mg / kg, and 1500 mg / kg of short-chain chlorinated paraffin samples to blank rubber, respectively, and homogenize them by rolling on a mixing mill. The spiked recoveries are 106.0%, 90.28%, 106.1%, and 94.56%, respectively. The relative standard deviations are 5.6%, 4.4%, 3.6%, and 4.3%, respectively. The requirements of the analytical method for recovery rate and reproducibility are met.

[0034] It can be seen from the above examples that the detection method provided by the present invention is accurate, and the accuracy of the result is not affected by the type of short-chain chlorinated paraffin used and the different standards, and can meet the detection requirements of short-chain chlorinated paraffin in rubber.

[0035] The above-mentioned example is only a preferred solution of the present invention and does not limit the present invention in any form. There are other changes and improvements without exceeding the technical solution described in the claims.

Claims

1. A method for determining short-chain chlorinated paraffins in rubber. It is characterized in that The following steps are involved: Weighing a rubber sample and an extraction solvent, mixing them for extraction, and obtaining an extract; The extract and concentrated sulfuric acid are mixed and then centrifuged using a centrifuge, and the concentrated sulfuric acid layer is discarded to obtain a test solution; and the test is performed using GC-NCI-MS; Qualitative analysis: Select short-chain chlorinated paraffin standard solution for repeated measurement, and conduct qualitative analysis based on chromatographic peak retention time, relative abundance of characteristic ions between monomers, and peak shape; Quantitative analysis: Select short-chain chlorinated paraffin standard solutions with a concentration of 10 mg / L and chlorine contents of 51.5%, 52.3%, 55.5%, 59.55%, and 63.0%; repeat the test three times; add the peak areas of 24 monomers, and calculate the total response factor by the ratio of the total peak area and concentration; establish a standard curve of chlorine content and total response factor; Sample testing: Test the test solution according to the test conditions of GC-NCI-MS, obtain the total ion current diagram for qualitative analysis; bring it into the standard curve to calculate the concentration of short-chain chlorinated paraffins.

2. According to the method for determining short-chain chlorinated paraffins in rubber according to claim 1, weigh 0.5 g of rubber sample and cut it into particles smaller than 1 cm×1 cm×1 cm, and ultrasonicate it in a 60°C water bath for 1 hour to obtain an extract, and the extract used is n-hexane including but not limited to.

3. According to the method for determining short-chain chlorinated paraffins in rubber as described in claim 1, the extract and concentrated sulfuric acid are mixed in a ratio of 1:1 and then centrifuged using a centrifuge, the concentrated sulfuric acid layer is discarded, and the above process is repeated 1 to 3 times until the lower sulfuric acid solution is clear to obtain a test solution.

4. The method for determining short-chain chlorinated paraffins in rubber according to claim 1, the test conditions of GC-NCI-MS are as follows: chromatographic column DB-5MS capillary column, 30m×0.25mm×0.1μm; injection port temperature: 300°C; column temperature: programmed temperature, 100°C to 300°C at 20°C / min, maintained for 5min; ion source temperature: 200°C; mass scanning range: 50amu~550amu; reaction gas: methane gas; solvent delay: 5min.

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