Method for detecting short-chain chlorinated paraffins in finished oil

Abstract

The application belongs to the field of analytical chemistry, and discloses a method for detecting short-chain chlorinated paraffins in finished oil products. The method comprises the following steps: S1. using an alumina filler chromatographic column to separate a finished oil sample to which an extraction internal standard is added; S2. using a Florisil small column to preliminarily purify the eluent obtained in S1; S3. using a graphitized carbon black small column to purify the preliminarily purified liquid obtained in S2; S4. nitrogen blowing concentration of the deeply purified liquid obtained in S3, adding an injection internal standard and using methanol to make up to obtain a sample to be measured; S5. using liquid chromatography tandem high-resolution mass spectrometry to measure the sample to be measured, and quantifying by an internal standard method. The method disclosed in the application can effectively separate short-chain chlorinated paraffins from finished oil samples with highly complex organic components, the accuracy of identification of short-chain chlorinated paraffins is improved by using high-resolution mass spectrometry, and the accuracy of quantitative results is further improved by introducing correction of isotopic extraction internal standards and isotopic injection internal standards.

Description

Technical Field

[0001] This invention belongs to the field of analytical chemistry technology, specifically relating to a method for detecting short-chain chlorinated paraffins in refined oil products. Background Technology

[0002] Short-chain chlorinated paraffins (SCCPs) are a class of carbon chains with a length of C2. 10 ~C 13 Straight-chain chlorinated hydrocarbons (SCCPs) with a chlorine content of 48%–70% were once widely used in petrochemical and other fields due to their good chemical stability, thermal stability, and electrical insulation properties. Historically, SCCPs were used as functional additives such as extreme pressure wear-resistant agents, flame retardants, and lubricants, added during the production of refined oil products like gasoline and diesel. However, SCCPs are also typical persistent organic pollutants (POPs), characterized by persistence, bioaccumulation, long-distance environmental migration, and significant biotoxicity. Refined oil products have been a frequent user of SCCPs. Establishing analytical methods suitable for SCCPs in refined oil products can clarify their occurrence characteristics, thus providing data support for source control and emission reduction of SCCPs.

[0003] Currently, instrumental analysis methods for SCCPs mainly include gas chromatography-electron capture negative chemical ionization source mass spectrometry (GC-ECNI-MS), two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOF-MS), and gas chromatography-high resolution mass spectrometry (GC-HRMS). For sample pretreatment, solid media typically employ Soxhlet extraction, accelerated solvent extraction, or ultrasound-assisted extraction, while liquid samples often utilize liquid-liquid extraction or solid-phase extraction techniques for enrichment and purification. Although these methods have achieved some application in specific fields, research on detection methods for SCCPs in refined oil matrices remains very limited. Existing detection methods are mostly applicable to relatively simple matrices such as textiles, food, water, or soil. When faced with refined oil samples rich in alkanes, cycloalkanes, aromatics, and various additives, and with severe matrix interference, applying existing methods generally results in poor sample pretreatment and purification, severe matrix interference, and excessively high detection limits. Furthermore, SCCPs themselves consist of various homologues and isomers, and the diversity of carbon chain lengths and chlorination degrees results in complex clustered peak distributions in their chromatographic analysis, making qualitative and quantitative analysis far more challenging than that of conventional organic pollutants. Therefore, there is an urgent need to develop a SCCPs detection method that combines high selectivity, high sensitivity, and good resistance to matrix interference, specifically tailored to the matrix characteristics of refined oil products, to meet the increasingly stringent regulatory requirements and the practical needs of environmental risk monitoring. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] Given the current lack of analytical methods for short-chain chlorinated paraffins in refined oil products, this invention creatively employs a combination of multiple column separation methods, taking advantage of the differences between the target short-chain chlorinated paraffins and the alkanes, cycloalkanes, and aromatics in the refined oil matrix. The sample undergoes multi-stage purification using alumina chromatography columns, Florisil columns, and graphitized carbon black columns, effectively reducing the matrix effect and achieving effective purification and enrichment of the target short-chain chlorinated paraffins, thereby improving the detection sensitivity. This invention uses liquid chromatography-tandem high-resolution mass spectrometry (HPLC-MS / MS) to detect the purified sample. Utilizing the instrument's high separation and resolution, it achieves the identification of complex homologues of short-chain chlorinated paraffins. Combined with optimization of the chlorine content standard curve, it achieves precise quantification of short-chain chlorinated paraffins. The method provided by this invention is characterized by low operational difficulty, high selectivity, high sensitivity, and low detection limit, making it suitable for screening new short-chain chlorinated paraffin contaminants in refined oil products and providing an effective analytical tool for tracing the source of new contaminants.

[0006] To achieve the above and other related objectives, the present invention provides a method for detecting short-chain chlorinated paraffins in refined oil products, the method comprising:

[0007] S1. Sample separation, including: adding the finished oil containing the extracted internal standard to a chromatography column packed with alumina, and eluting by gradient to obtain the target eluent.

[0008] S2, Sample purification I, including: adding the target eluent dropwise onto an activated Florisil column, and eluting to obtain purified solution I.

[0009] S3. Sample purification II, including: adding purification solution I dropwise onto the activated graphitized carbon black column and eluting to obtain purification solution II.

[0010] S4. Sample volume adjustment, including: nitrogen blowing concentration of purification solution II, addition of injection internal standard, and reconstitution with methanol to adjust the volume.

[0011] S5. Sample detection, including: determining the concentration of short-chain chlorinated paraffins using liquid chromatography-tandem ion trap high-resolution mass spectrometry, and calculating the concentration by substituting the values ​​into the standard curve.

[0012] As a preferred embodiment of the method for detecting short-chain chlorinated paraffins in refined oil products according to the present invention, wherein: the short-chain chlorinated paraffins have a chain length of C 10 To C13 The product contains straight-chain chlorinated hydrocarbons with a chlorine content exceeding 48% by weight; the finished oil includes various grades of gasoline and diesel.

[0013] As a preferred embodiment of the method for detecting short-chain chlorinated paraffins in refined oil products according to the present invention, wherein: the extraction of internal standard in step S1 is... 13 C isotope-labeled hexachlorodecane, the internal standard for injection in step S4 is... 13 C isotope-labeled trans-chlordane.

[0014] As a preferred embodiment of the detection method for short-chain chlorinated paraffins in the finished oil of the present invention, the alumina mentioned in step S1 is alumina deactivated by 5% water by weight. The specific preparation method is to activate the alumina by calcining it at 500°C for 6 hours, cool the activated alumina to room temperature in a desiccator, and add water to the activated alumina at 5% by weight to deactivate it, thereby obtaining alumina filler deactivated by 5% water.

[0015] Preferably, the amount of deactivated alumina packed into the chromatography column in step S1 is 20g.

[0016] As a preferred embodiment of the method for detecting short-chain chlorinated paraffins in finished oil products according to the present invention, the gradient elution method in step S1 involves sequentially eluting the chromatography column with 30 mL of pure n-hexane, 30 mL of a mixed solution of n-hexane / dichloromethane (v:v=4:1), and 30 mL of a mixed solution of n-hexane / dichloromethane (v:v=1:1).

[0017] As a preferred embodiment of the method for detecting short-chain chlorinated paraffins in finished oil products according to the present invention, the target short-chain chlorinated paraffins are eluted in two hexane / dichloromethane solutions of different ratios, the two hexane / dichloromethane mixed solutions are combined and collected, and concentrated to 1 mL to obtain the target eluent.

[0018] As a preferred embodiment of the method for detecting short-chain chlorinated paraffins in the finished oil product of the present invention, wherein the Florisil column used in step S2 of the present invention has a specification of 6cc and 500mg.

[0019] As a preferred embodiment of the method for detecting short-chain chlorinated paraffins in refined oil products according to the present invention, the activation method of the Florisil column involves sequentially activating it with a column volume of a hexane / dichloromethane (v:v=4:1) mixed solution and a column volume of hexane.

[0020] As a preferred embodiment of the detection method for short-chain chlorinated paraffins in the finished oil products of the present invention, the elution method of the Florisil column is to drop the target eluent onto the column and elute sequentially with one column volume of n-hexane and one column volume of n-hexane / dichloromethane (v:v=4:1) mixed solution.

[0021] As a preferred embodiment of the method for detecting short-chain chlorinated paraffins in the finished oil product of the present invention, the purified liquid I is obtained by combining and collecting the two eluents and then concentrating them by nitrogen blowing.

[0022] As a preferred embodiment of the detection method for short-chain chlorinated paraffins in the finished oil product of the present invention, the graphitized carbon black column used in step S3 of the present invention has a specification of 3cc and 250mg.

[0023] As a preferred embodiment of the detection method for short-chain chlorinated paraffins in the finished oil product of the present invention, the activation method of the graphitized carbon black column is to activate it with a mixed solution of acetonitrile / toluene (v:v=3:1) with a column volume of one column.

[0024] As a preferred embodiment of the detection method for short-chain chlorinated paraffins in the finished oil product of the present invention, the elution method of the graphitized carbon black column is to add purification solution I dropwise onto the column and elute with a mixed solution of acetonitrile / toluene (v:v=3:1) of one column volume to obtain purification solution II.

[0025] As a preferred embodiment of the method for detecting short-chain chlorinated paraffins in the finished oil product of the present invention, in step S4, the purified liquid II is concentrated to near dryness by nitrogen blowing with high-purity nitrogen gas, and then the internal standard is added and the volume is adjusted with methanol.

[0026] As a preferred embodiment of the method for detecting short-chain chlorinated paraffins in the finished oil product of the present invention, in step S5, the liquid chromatography uses a Vanquish high-performance liquid chromatograph and an ACQUITY CSH C18 column (2.1 mm × 100 mm, 1.7 μm).

[0027] As a preferred embodiment of the method for detecting short-chain chlorinated paraffins in refined oil products according to the present invention, the liquid chromatography conditions include: a flow rate of 0.2 mL / min; mobile phase A being pure water; mobile phase B being a 10 μM methanol solution of tetraphenylphosphine chloride; and a mobile phase gradient of 60.0% and 40.0% for mobile phase A and mobile phase B respectively during the 0.0~2.0 min interval, 0.0% for mobile phase A and 100.0% for mobile phase B respectively during the 6.0~16.0 min interval, and 60.0% for mobile phase A and 40.0% for mobile phase B respectively during the 16.5~20.0 min interval.

[0028] As a preferred embodiment of the method for detecting short-chain chlorinated paraffins in the finished oil product of the present invention, the liquid chromatography conditions include: column temperature set at 40°C; injection volume of 5 μL.

[0029] As a preferred embodiment of the method for detecting short-chain chlorinated paraffins in refined oil products according to the present invention, in step S5, the mass spectrometer used is an ion trap high-resolution mass spectrometer.

[0030] As a preferred embodiment of the method for detecting short-chain chlorinated paraffins in refined oil products according to the present invention, the mass spectrometry conditions include: using an electrospray ionization (ESI) source, performing daughter ion scanning in negative ion mode, with a spray voltage of 2500 V, an ion transmission tube temperature of 275℃, an evaporator temperature of 300℃, a resolution of 120000, and a scanning range of 200~1800 (m / z).

[0031] As a preferred embodiment of the detection method for short-chain chlorinated paraffins in the finished oil products of the present invention, in step 5, quantitative analysis is performed by plotting standard curves of short-chain chlorinated paraffins with different chlorine percentages, wherein the linearity coefficient of the standard curves is greater than 0.99.

[0032] Beneficial effects of this invention:

[0033] (1) This invention utilizes an alumina chromatography column to separate the integral component with similar polarity to short-chain chlorinated paraffins. Then, through a gradient combination of Florisil and graphitized carbon black solid-phase extraction columns, the remaining organic compounds, such as hydrocarbons and benzene series compounds, are purified. The combined use of multiple purification methods ultimately achieves the goal of reducing interference from complex organic matrices in petroleum, realizing the effective determination of the target short-chain chlorinated paraffins. This invention also utilizes high-performance liquid chromatography tandem high-resolution mass spectrometry to accurately determine the mass number of short-chain chlorinated paraffins, effectively separating homologues and medium-chain chlorinated paraffins, significantly improving the accuracy of qualitative and quantitative analysis.

[0034] (2) The method provided by this invention achieves accurate quantification of short-chain chlorinated paraffins in refined oil products. The average recovery rate of the method is between 52.45% and 132.30%, the detection limit is as low as 12.5 ng / g, and the correlation coefficient of the chlorine content standard curve is above 0.99. This method has good purification effect, high recovery rate, and low detection limit, meeting the basic analytical requirements and can be used for the analysis and detection of short-chain chlorinated paraffins in refined oil products. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0036] Figure 1 This is a flowchart of the analytical testing process for short-chain chlorinated paraffins in finished oil products according to the present invention.

[0037] Figure 2 The chromatograms are of the internal standard extracted and the injected internal standard in Example 1.

[0038] Figure 3 This is a standard curve of chlorine content in short-chain chlorinated paraffins plotted in Example 1.

[0039] Figure 4 This is a comparison chart of the finished oil sample to be purified in Example 3 and the sample purified using this method.

[0040] Figure 5 This is a comparison diagram of the test solutions obtained in Comparative Example 2 and Example 3.

[0041] Figure 6 The total ion current (TIC) chromatogram is shown for the sample measured in Comparative Example 2.

[0042] Figure 7 The total ion current (TIC) chromatogram is shown for the sample measured in Example 3. Detailed Implementation

[0043] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0044] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0045] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0046] The instrument and equipment information used in the embodiments of this invention is as follows: Orbitrap Exploris 240 liquid chromatography-tandem ion trap high-resolution mass spectrometer (Thermo Scientific, USA); ACQUITY CSH C18 column (2.1 mm × 100 mm, 1.7 μm, Waters Corporation, USA); LC-DCY-24G dry nitrogen blower (Shanghai Lichen Technology Co., Ltd.); vortex mixer (Shanghai Huxi Industrial Co., Ltd.); solid phase extraction device (Tianjin Autoshine Instruments Co., Ltd.), etc.

[0047] The reagents and standards used in the embodiments of this invention are as follows: Methanol (mass spectrometry grade, Thermo Scientific, USA); acetonitrile, n-hexane, isopropanol (chromatographic grade, Thermo Scientific, USA); dichloromethane, chloroform, toluene (chromatographic grade, Shanghai Bailingwei Chemical Technology Co., Ltd.); tetraphenylphosphine chloride (purity 98.5%, Shanghai Bailingwei Chemical Technology Co., Ltd.); alumina (98%, Shanghai Titan Technology Co., Ltd.). 13 C 10 - Hexachlorodecane standard solution 13 C 10 - Trans-chlordane standard solution (99% purity, Shanghai Bailingwei Chemical Technology Co., Ltd.); Short-chain chlorinated paraffin standard solutions (chlorine contents of 51.0%, 55.5%, and 63% respectively) (Dr. Ehrenstorfer GmbH, Germany); All experimental water was ultrapure water, and all other reagents were of analytical grade or higher; Floris silica columns and graphitized carbon black columns (Shanghai Titan Technology Co., Ltd.).

[0048] Example 1

[0049] This embodiment provides a method for detecting short-chain chlorinated paraffins in refined oil products, referring to... Figure 1 Specifically:

[0050] S1. Sample Separation

[0051] Alumina was activated by calcination at 500 °C for 6 hours. The activated alumina was then cooled to room temperature in a desiccator. Water was added at 5% by weight to the activated alumina for deactivation, yielding a 5% water-deactivated alumina packing. 20 g of deactivated alumina was packed into a single chromatography column. 100 μL of n-hexane was added dropwise to the top of the column as a blank, followed by 20–50 ng of [unspecified ingredient]. 13 C 10- Hexachlorodecane was used as the internal standard for extraction. The column was eluted sequentially with 30 mL of pure n-hexane, 30 mL of a hexane / dichloromethane (v:v=4:1) mixture, and 30 mL of a hexane / dichloromethane (v:v=1:1) mixture. The last two hexane / dichloromethane mixtures were collected and concentrated to 1 mL to obtain the target eluent.

[0052] S2. Sample Cleaning I

[0053] Purification was performed using a 6cc, 500mg Florisil column. The Florisil column was activated sequentially with one column volume of a hexane / dichloromethane (v:v=4:1) mixture and one column volume of hexane. The target eluent was added dropwise to the column, and then eluted sequentially with one column volume of hexane and one column volume of a hexane / dichloromethane (v:v=4:1) mixture. The two eluents were combined and concentrated by nitrogen blowing to obtain purified solution I.

[0054] S3. Sample Purification II

[0055] Graphitized carbon black columns with a specification of 3cc and 250mg were used. The graphitized carbon black columns were activated with one column volume of acetonitrile / toluene (v:v=3:1) mixed solution. Purification solution I was added dropwise to the columns and eluted with one column volume of acetonitrile / toluene (v:v=3:1) mixed solution to obtain purification solution II.

[0056] S4. Sample volume adjustment

[0057] At 40°C, the purified liquid II was concentrated to near dryness using high-purity nitrogen gas, and then 20-50 ng of [unspecified substance] was added. 13 C 10 - Trans-chlordane was used as an internal standard for injection. The sample was redissolved in methanol and then vortexed to mix.

[0058] S5. Sample Testing

[0059] The target analyte was detected using a high-performance liquid chromatography-tandem ion trap high-resolution mass spectrometer. The chromatographic conditions were set as follows: ACQUITY CSH C18 column (2.1 mm × 100 mm, 1.7 μm); column temperature was set to 40 °C; injection volume was 5 μL; mobile phase A was pure water; mobile phase B was a 10 μM tetraphenylphosphine chloride methanol solution; flow rate was 0.2 mL / min; and the mobile phase gradient is shown in Table 1.

[0060] Table 1 Mobile Phase Gradient Table for Liquid Chromatography

[0061] The mass spectrometry conditions were set as follows: Electrospray ionization (ESI) was used, with daughter ion scanning in negative ion mode. The spray voltage was 2500 V, the ion transfer tube temperature was 275℃, the evaporator temperature was 300℃, the resolution was 120,000, and the scan range was 200–1800 m / z. Internal standard was extracted (…). 13 C 10 -hexachlorodecane) and internal standard ( ) 13 C 10 -The chromatogram of trans-chlordane is as follows: Figure 2 As shown

[0062] A gradient of short-chain chlorinated paraffin standards with different chlorine contents was prepared, and a standard curve was plotted with the percentage of chlorine content on the x-axis and the relative total response factor on the y-axis. The standard curve is shown below. Figure 3 As shown. When calculating the content of short-chain chlorinated paraffins in an actual sample, the total response factor and relative total area of ​​short-chain chlorinated paraffins in the sample are calculated, and the concentration of short-chain chlorinated paraffins in the actual sample can be obtained by conversion.

[0063] The above steps S1 to S5 were repeated five times as five parallel blank experiments. The recovery rate of the extracted internal standard was 71.07 ± 6.79%, indicating high method accuracy. The relative standard deviation was 9.55%, which is less than 15%, demonstrating good method precision.

[0064] Example 2

[0065] This embodiment differs from Embodiment 1 in that: during sample separation in step S1, after adding 100 μL of n-hexane to the top layer of the chromatography column, 5000 ng of short-chain chlorinated paraffin is added, followed by further addition of... 13 C 10 - Hexachlorodecane was used as the internal standard for extraction, and all other steps were consistent with those in Example 1.

[0066] The above steps were repeated five times as five standard spiking recovery experiments. The recovery rate of the internal standard extracted from the samples was 52.96 ± 5.92%, with a relative standard deviation of 11.18%. The recovery rate of the standard spiking was 70.20 ± 4.11%, with a relative standard deviation of 5.85%. The recovery rates of the parallel samples were all greater than 40%, which meets the recovery rate requirements for trace substance analysis, demonstrating good method accuracy. The relative standard deviations of less than 15% all demonstrate the high precision of the analytical method.

[0067] Furthermore, the limit of detection (LOD) for short-chain chlorinated paraffins in refined oil products was determined. Specifically, the LOD of the target short-chain chlorinated paraffins was calculated using a signal-to-noise ratio (S / N) of 3, and the LOD obtained by the method of this invention was 12.5 ng / g.

[0068] Example 3

[0069] This embodiment differs from Embodiment 1 in that: during the sample separation process in step S1, 100 μL of diluted No. 92 gasoline sample is added dropwise to the top layer of the chromatography column, followed by a certain amount of... 13 C 10 Hexachlorodecane was used as the internal standard for extraction; all other steps remained consistent with Example 1. A comparison of the final purified oil sample and the sample purified using this method is shown in the figure below. Figure 4 As shown.

[0070] The actual measured concentration of short-chain chlorinated paraffins in the target 92-octane gasoline was 332.03 ng / g, and the sample extraction recovery rate was 74.13%.

[0071] Comparative Example 1

[0072] The difference between this comparative example and Example 3 is that S2. Sample purification I and S3. Sample purification II are not performed during the analysis process. Specifically: Alumina was activated by calcination at 500 °C for 6 hours. The activated alumina was then cooled to room temperature in a desiccator. Water was added at a weight ratio of 5% to the activated alumina for deactivation, yielding a 5% water-deactivated alumina packing. 20g of deactivated alumina was packed into a single chromatography column. 100μL of 92# gasoline was added dropwise to the top layer of the column. 13 C 10 - Hexachlorodecane was used as the internal standard for extraction. The column was eluted sequentially with 30 mL of pure n-hexane, 30 mL of a hexane / dichloromethane (v:v=4:1) mixture, and 30 mL of a hexane / dichloromethane (v:v=1:1) mixture. The last two hexane / dichloromethane mixtures were collected and added to... 13 C 10 - Trans-chlordane was used as an internal standard for injection, concentrated to 1 mL, and then vortexed to mix. The target analyte was detected using high-performance liquid chromatography-tandem ion trap high-resolution mass spectrometry. The liquid chromatography and mass spectrometry conditions were set the same as in Example 1, and the quantitative calculation method was the same as in Example 1.

[0073] The recovery rate of the sample in Comparative Example 1 was only 20.31%, less than 40%, which does not meet the relevant requirements for analytical chemistry testing. Furthermore, Comparative Example 1 also exhibited extremely severe matrix interference, further affecting the accuracy of quantitative analysis.

[0074] Comparative Example 2

[0075] The difference between this comparative example and Example 3 is that S3. Sample purification II is not performed. Specifically: Alumina was activated by calcination at 500 °C for 6 hours. The activated alumina was then cooled to room temperature in a desiccator. Water was added at a weight ratio of 5% to the activated alumina for deactivation, yielding a 5% water-deactivated alumina packing. 20g of deactivated alumina was packed into a single chromatography column. 100μL of 92# gasoline was added dropwise to the top layer of the column. 13 C 10 - Hexachlorodecane was used as the internal standard for extraction. The column was eluted sequentially with 30 mL of pure n-hexane, 30 mL of a hexane / dichloromethane (v:v=4:1) mixture, and 30 mL of a hexane / dichloromethane (v:v=1:1) mixture. The two hexane / dichloromethane mixtures were combined and concentrated to 1 mL. A 6 cc, 500 mg Florisil column was activated sequentially with one column volume of hexane / dichloromethane (v:v=4:1) mixture and one column volume of hexane. The concentrated liquid was added dropwise to the column, followed by elution with one column volume of hexane and one column volume of hexane / dichloromethane (v:v=4:1) mixture. The two eluates were combined and evaporated to near dryness under nitrogen. Add... 13 C 10 - Trans-chlordane was used as an internal standard for injection, concentrated to 1 mL, and then vortexed to mix. The target analyte was detected using high-performance liquid chromatography-tandem ion trap high-resolution mass spectrometry. The liquid chromatography and mass spectrometry conditions were set the same as in Example 1, and the quantitative calculation method was the same as in Example 1.

[0076] The recovery rate of the sample in Comparative Example 2 was 45.23%, which basically meets the relevant requirements for analytical chemistry testing. Compared with Comparative Example 1, the sample recovery rate was significantly increased, while the matrix interference effect was correspondingly reduced, and the sample color became significantly lighter, indicating that adding Florisil column purification can effectively reduce the interference of complex organic matrices in the sample. Comparative Example 2 and Example 3 show... Figure 5 As shown, the test solution obtained in Comparative Example 2 was still pale yellow, while the test solution obtained in Example 3 was clear and transparent. Further comparison was made using total ion current intensity, as... Figure 6 and Figure 7 As shown, Figure 6 The image shows the total ion current (TIC) plot of the sample measured in Comparative Example 2, with a total ion current intensity of 1.45 × 10⁻⁶. 9 , Figure 7 The image shows the total ion current (TIC) plot of the sample measured in Example 3, with a total ion current intensity of 5.40 × 10⁻⁶. 8In comparison, the total ion chromatograms of the two studies show a significant reduction in matrix effect and a marked improvement in peak shape. The decrease in total ion current intensity also indicates a reduction in matrix effect. Comparative Example 2 still exhibits a significant matrix interference effect, and the recovery rate obtained in Comparative Example 2 is lower than that in Example 3. This indicates that the graphitized carbon black column purification added in Example 3 can further reduce the matrix effect, thereby significantly improving instrument sensitivity and response value. At the same time, the added pretreatment step does not cause a significant loss in sample recovery rate.

[0077] The actual results of Comparative Examples 1, 2, and 3 demonstrate the effectiveness and scientific validity of the multi-step pretreatment. Although the added pretreatment steps increase the experimental procedure, they do not significantly reduce the sample recovery rate. At the same time, they can effectively remove the interference effect of complex organic matrix and further improve the sensitivity of instrument analysis, thereby ensuring the accuracy of the measurement results.

[0078] In summary, the method provided by this invention can effectively detect short-chain chlorinated paraffins in refined oil products. The method exhibits good recovery and a low detection limit, providing a feasible method for pretreatment of refined oil samples with complex matrices. The method provided by this invention can provide strong support for tracing the sources of novel short-chain chlorinated paraffin contaminants.

[0079] The detection steps for short-chain chlorinated paraffins in refined oil products are as follows: Step S1 uses an alumina chromatography column to collect polar components similar to short-chain chlorinated paraffins, initially removing other polar organic interferences; Step S2 uses a Florisil column for separation, enhancing sample resolution and further separating the target short-chain chlorinated paraffins; Step S3 further uses a graphitized carbon black column to adsorb residual benzene compounds and hydrocarbons, further purifying the sample; Step S4 concentration ensures batch-to-batch stability of the sample and increases the loading of the target analyte during detection; Step S5 uses high-performance liquid chromatography tandem with high-resolution mass spectrometry to detect the target analyte. Under optimized chromatographic and mass spectrometric conditions, accurate quantification of the target short-chain chlorinated paraffins is achieved. The total response factor, corrected for internal standards, is then used to quantify the short-chain chlorinated paraffins in the sample, thus obtaining accurate quantitative results. This invention achieves effective analysis of short-chain chlorinated paraffins in refined oil products, effectively eliminating severe matrix interference in refined oil products, improving detection sensitivity, and lowering the detection limit.

[0080] 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 it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for detecting short-chain chlorinated paraffins in refined oil products, characterized in that: include, The finished oil containing the extracted internal standard was added dropwise onto a chromatography column packed with alumina, and gradient elution was performed to obtain the target eluent. The target eluent was added dropwise onto an activated Florisil column, and the purified solution I was obtained by elution. Purification solution I was added dropwise onto a column of activated graphitized carbon black and eluted to obtain purification solution II; Purification solution II was concentrated by nitrogen blowing, and after adding the internal standard for injection, it was reconstituted and diluted to volume with methanol. The concentration of short-chain chlorinated paraffins was determined using liquid chromatography-tandem ion trap high-resolution mass spectrometry, and the concentration was calculated by substituting the values ​​into the standard curve.

2. The method for detecting short-chain chlorinated paraffins in refined oil products as described in claim 1, characterized in that: The short-chain chlorinated paraffin has a chain length of C. 10 To C 13 The finished oil contains straight-chain chlorinated hydrocarbons with a chlorine content exceeding 48% by weight; the finished oil includes various grades of gasoline and diesel.

3. The method for detecting short-chain chlorinated paraffins in refined oil products as described in claim 1 or 2, characterized in that: The extracted internal standard is 13 C isotope-labeled hexachlorodecane.

4. The method for detecting short-chain chlorinated paraffins in refined oil products as described in claim 1, characterized in that: The alumina is deactivated by adding ultrapure water at a mass ratio of 5%, and the packing amount is 20g.

5. The method for detecting short-chain chlorinated paraffins in refined oil products as described in claim 1 or 4, characterized in that: The gradient elution yields the target eluent by sequentially eluting with 30 mL of pure n-hexane, 30 mL of a 4:1 n-hexane / dichloromethane mixture, and 30 mL of a 1:1 n-hexane / dichloromethane mixture. The latter two n-hexane / dichloromethane mixtures are collected and concentrated to obtain the target eluent.

6. The method for detecting short-chain chlorinated paraffins in refined oil products as described in claim 1, characterized in that: The target eluent was added dropwise onto an activated Florisil column, and elution yielded purified solution I. The process involves sequentially activating a Florisil column with one column volume of a hexane / dichloromethane mixed solution at a volume ratio of 4:1 and one column volume of hexane. The target eluent is then added dropwise onto the column. Finally, the column is eluted sequentially with one column volume of hexane and one column volume of a hexane / dichloromethane mixed solution at a volume ratio of 4:

1. The eluents are combined, collected, and concentrated by nitrogen blowing to obtain purified solution I.

7. The method for detecting short-chain chlorinated paraffins in refined oil products as described in claim 1, characterized in that: The purification solution I is added dropwise to the activated graphitized carbon black column and eluted to obtain purification solution II. The process includes first activating the graphitized carbon black column with an acetonitrile / toluene mixed solution of one column volume and a volume ratio of 3:1, then adding purification solution I dropwise to the column, and finally eluting with an acetonitrile / toluene mixed solution of one column volume and a volume ratio of 3:1 to obtain purification solution II.

8. The method for detecting short-chain chlorinated paraffins in refined oil products as described in claim 1, characterized in that: The nitrogen blowing concentration temperature is 40°C, and the injected internal standard is... 13 C isotope-labeled trans-chlordane.

9. The method for detecting short-chain chlorinated paraffins in refined oil products as described in claim 1, characterized in that: The chromatographic conditions included: a C18 column with dimensions of 2.1 mm × 100 mm and a diameter of 1.7 μm; mobile phase A being pure water; mobile phase B being a 10 μM methanol solution of tetraphenylphosphine chloride; column temperature of 40 °C; injection volume of 5 μL; and flow rate of 0.2 mL / min.

10. The method for detecting short-chain chlorinated paraffins in refined oil products as described in claim 1 or 9, characterized in that: The conditions for the mass spectrometry include: an electrospray ion source, daughter ion scanning in negative ion mode, a spray voltage of 2500V, an ion transmission tube temperature of 275℃, an evaporator temperature of 300℃, a resolution of 120000, and a scanning range of 200~1800m / z.

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