Rapid detection method for determining hexamethyldisiloxane in soil

Abstract

The invention discloses a rapid detection method for determining hexamethyldisiloxane in soil, which comprises the following steps: S1, sample collection and preservation: collecting a soil sample according to the regulation of HJ / T 166, collecting 3 parallel samples by using a 40mL brown sample bottle, collecting a proper amount of sample into the sample bottle by using a sampler during sampling, and storing the sample in the sample bottle; quickly removing samples adhered to threads and outer surfaces of the sample bottles, sealing the sample bottles, refrigerating and transporting the sample bottles to a laboratory, preserving the sample bottles in a dark place at 4 DEG C or below, and completing analysis within 7 days; the method comprises the following steps: S1, sample pretreatment: measuring the moisture content of 5g of soil sample; weighing and recording a purging bottle filled with a sample, and putting the purging bottle on a purging and trapping device for detection; s2, preparing a standard curve: preparing hexamethyldisiloxane standard series solutions by taking methanol as a solvent; according to the method, the detection efficiency is high, complex extraction and purification steps are not needed in sample pretreatment, automatic detection is achieved through combination of purge-trap and chromatography-mass spectrometry, the detection period of a single sample is smaller than or equal to 30 min, and the requirement for rapid detection of large-batch samples is met.

Description

Technical Field

[0001] This invention relates to the field of soil environmental monitoring and analytical chemistry, and in particular to a rapid detection method for determining hexamethyldisiloxane in soil. Background Technology

[0002] Hexamethyldisiloxane is a volatile organic compound widely used in chemical, electronics, and pharmaceutical industries. It is highly volatile and difficult to degrade, and during production, storage, and use, it can easily enter the soil environment through leaks and emissions, damaging soil ecosystems and potentially accumulating in the food chain, thus posing a health risk. Therefore, establishing a rapid and accurate detection method for hexamethyldisiloxane in soil is of great significance for soil pollution investigation, risk assessment, and pollution remediation.

[0003] Currently, the main methods for detecting volatile organic compounds in soil include purge-trap / gas chromatography-mass spectrometry, headspace / gas chromatography, and solid-phase extraction / high-performance liquid chromatography. Among them, purge-trap / gas chromatography-mass spectrometry is widely used due to its advantages such as simple pretreatment, high enrichment efficiency, and low detection limit. However, the existing methods have the following shortcomings in the detection of hexamethyldisiloxane: (1) The sample pretreatment process is cumbersome and time-consuming, making it difficult to meet the rapid detection requirements of large batches of samples; (2) Insufficient optimization of instrument parameters leads to poor separation of target analytes and unstable response values; (3) The detection limit and precision of the method need to be improved, making it difficult to meet the detection requirements of low-concentration contaminated soil.

[0004] In view of this, the present invention establishes a rapid, sensitive and accurate method for detecting hexamethyldisiloxane in soil by optimizing sample collection and preservation methods, purge and trap parameters, and chromatographic-mass spectrometry detection conditions. It aims to solve the problems of low detection efficiency, insufficient sensitivity and large matrix interference in the existing technology. Summary of the Invention

[0005] The purpose of this invention is to provide a rapid detection method for determining hexamethyldisiloxane in soil in order to solve the above-mentioned problems.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A rapid detection method for determining hexamethyldisiloxane in soil includes the following steps:

[0008] S1. Sample collection and preservation: Soil samples were collected in accordance with HJ / T 166. Three parallel samples were collected using 40mL brown sample bottles. During sampling, an appropriate amount of sample was collected into the sample bottle using a sampler. The sample bottle was quickly cleaned of any sample adhering to the threads and outer surface of the sample bottle. The sample bottle was sealed and transported to the laboratory under refrigeration. The sample bottle was stored below 4℃ and protected from light. The analysis was completed within 7 days.

[0009] S2. Sample pretreatment: Take 5g of soil sample to determine the moisture content; weigh and record the weight of the purge bottle containing the sample and place it on the purge collection device for testing.

[0010] S3. Preparation of standard curve: Using methanol as solvent, prepare a series of hexamethyldisiloxane standard solutions with concentration gradients of 5, 10, 20, 50, 100, and 400 μg / L. Add substitute standard solutions and internal standard solutions to each standard solution to make the internal standard concentration 50 μg / L.

[0011] S4. Purge and trap treatment: Place the weighed 40mL purge bottle containing the sample on the fully automatic purge and trap device, purge and enrich with high-purity nitrogen, and obtain the target component after thermal desorption.

[0012] S5. Gas Chromatography-Mass Spectrometry Detection: The target component after thermal desorption is injected into the gas chromatograph for separation, and then detected by the mass spectrometer. The retention time and response value of the target analyte and internal standard are recorded.

[0013] S6. Qualitative and quantitative analysis: Qualitative analysis is performed by comparing with standard mass spectra and matching retention times. A standard curve is established with the ratio of the content of the target analyte to the internal standard as the abscissa and the ratio of the response value as the ordinate. The content of hexamethyldisiloxane in the soil is quantitatively calculated using the internal standard method.

[0014] S7. Data Validation: Quality control of test results is carried out through precision experiments, recovery rate experiments, and detection limit validation.

[0015] Preferably, the method for determining the moisture content in step S2 is as follows: take 5g (accurate to 0.01g) of sample and dry it at (105±5)℃ for at least 6h. Calculate the moisture content w (%) of the sample by dividing the difference in sample mass before and after drying by the mass of the sample before drying and then multiplying by 100, accurate to 0.1%.

[0016] Preferably, the operating conditions of the purge trap in step S4 are as follows: purge flow rate 40 mL / min, purge temperature 20℃, purge time 11 min, dry purge time 2 min, pre-desorption temperature 245℃, desorption temperature 250℃, desorption time 2 min, baking temperature 280℃, and baking time 10 min.

[0017] Preferably, the operating conditions of the gas chromatograph in step S5 are as follows: the chromatographic column is DB-624, the injection port temperature is 220℃, the split ratio is 60:1, the temperature program is as follows: initial temperature 38℃ held for 1.8 min, temperature increased to 120℃ at 10℃ / min, then temperature increased to 240℃ at 15℃ / min held for 6 min, and the column flow rate is 1.0 mL / min.

[0018] Preferably, the operating conditions of the mass spectrometer in step S5 are as follows: ion source temperature 230℃, transfer line temperature 250℃, quadrupole temperature 150℃, ion source electron energy 70eV, mass scan range 35~270amu, and data acquisition mode is full scan mode.

[0019] Preferably, in step S3, the substitute standard solution is a mixed solution of three substitutes in methanol, and the internal standard solution is a mixed standard solution of three internal standards in methanol.

[0020] Preferably, in step S7, the method detection limit is 0.5 μg / kg, the determination limit is 2.0 μg / kg, the spiked recovery rate of soil samples is 90.0%~111%, the spiked recovery rate of sediment samples is 87.0%~115%, and the relative standard deviation is ≤3.6%.

[0021] Preferably, in step S1, a portable volatile organic compound detector can be used for on-site preliminary screening during sampling. The sample bottle must be sealed immediately after sampling to avoid loss due to volatilization of the target substance.

[0022] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0023] 1. In this application, the detection efficiency is high: sample pretreatment does not require complicated extraction and purification steps, and purge-trap combined with chromatography-mass spectrometry achieves automated detection. The detection cycle for a single sample is ≤30min, which meets the needs of rapid detection of large batches of samples.

[0024] 2. In this application, by optimizing the purge and trap parameters and mass spectrometry detection conditions, the method detection limit is as low as 0.5 μg / kg and the determination limit is 2.0 μg / kg, which can accurately detect hexamethyldisiloxane in low concentrations of contaminated soil.

[0025] 3. In this application, the internal standard method is used for quantification, which effectively eliminates matrix interference and instrument fluctuation. The linear correlation coefficient R of the standard curve is ≥0.9998, the spiked recovery rate of soil samples is 90.0%~111%, and the spiked recovery rate of sediment samples is 87.0%~115%, and the detection results are reliable.

[0026] 4. This application is applicable to the detection of different types of soil and sediment samples. The instruments and equipment are conventional laboratory equipment, easy to operate, and easy to promote and apply.

[0027] 5. In this application, the stability is excellent: by optimizing sample preservation conditions and instrument parameters, the method precision RSD is ≤3.6%, the detection results are stable, and the quality control requirements for environmental monitoring are met. Attached Figure Description

[0028] Figure 1 The total ion chromatogram of a hexamethyldisiloxane standard sample provided according to an embodiment of the present invention is shown;

[0029] Figure 2 A schematic diagram of instrument and equipment verification provided according to an embodiment of the present invention is shown;

[0030] Figure 3 A schematic diagram illustrating the verification of standard substances and reagents provided according to embodiments of the present invention is shown. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Please see Figure 1-3 The present invention provides a technical solution:

[0033] A rapid detection method for determining hexamethyldisiloxane in soil includes the following steps:

[0034] S1. Sample collection and preservation: Soil samples were collected in accordance with HJ / T 166. Three parallel samples were collected using 40mL brown sample bottles. During sampling, an appropriate amount of sample was collected into the sample bottle using a sampler. The sample bottle was quickly cleaned of any sample adhering to the threads and outer surface of the sample bottle. The sample bottle was sealed and transported to the laboratory under refrigeration. The sample bottle was stored below 4℃ and protected from light. The analysis was completed within 7 days.

[0035] S2. Sample pretreatment: Take 5g of soil sample to determine the moisture content; weigh and record the weight of the purge bottle containing the sample and place it on the purge collection device for testing.

[0036] Moisture content determination: Take 5.00g of soil sample (accurate to 0.01g) and place it in a clean crucible. Dry it in an oven at (105±5)℃ for at least 6h. After cooling to room temperature, weigh it and calculate the moisture content according to the formula for subsequent result correction.

[0037] S3. Preparation of standard curve: Using methanol as solvent, prepare a series of hexamethyldisiloxane standard solutions with concentration gradients of 5, 10, 20, 50, 100, and 400 μg / L. Add substitute standard solutions and internal standard solutions to each standard solution to make the internal standard concentration 50 μg / L.

[0038] Substitutes and internal standards were added: appropriate amounts of substitute standard solutions (a mixed solution of three substitutes in methanol, concentration 2000 μg / mL) and internal standard solutions (fluorobenzene in methanol, concentration 2000 μg / mL) were added to each standard series solution to make the internal standard concentration 50.0 μg / L, and the concentration of substitutes matched the concentration of target analytes.

[0039] Curve establishment: Using an airtight syringe, 5.00 mL of the above standard solution was measured into 40 mL sample vials. The concentrations were measured sequentially from low to high according to the instrument reference conditions. The ratio of the content of the target analyte to the internal standard was used as the abscissa (x), and the ratio of their response values ​​was used as the ordinate (y). A linear regression equation was established, and the correlation coefficient was calculated.

[0040] S4. Purge and trap treatment: Place the weighed 40mL purge bottle containing the sample on the fully automatic purge and trap device, purge and enrich with high-purity nitrogen, and obtain the target component after thermal desorption.

[0041] Instrument selection: The ATOMX / XYZ purge and trap instrument was used, and the instrument passed the functional verification.

[0042] Sample injection: The instrument automatically injects samples according to the preset program.

[0043] Purging and enrichment: High-purity nitrogen (purity ≥99.999%) was introduced for purging at a flow rate of 40 mL / min, a purging temperature of 20℃, and a purging time of 11 min, so that hexamethyldisiloxane in the sample was fully enriched in the collection tube; dry purging time was 2 min to remove residual moisture in the collection tube.

[0044] Thermal desorption: The pre-desorption temperature of the collection tube is 245℃, the desorption temperature is 250℃, the desorption time is 2min, high-purity helium gas (purity ≥99.999%) is introduced for backflushing, and the target component is blown into the gas chromatograph.

[0045] Instrument cleaning: After each test, the collection tube is baked at 280℃ for 10 minutes to remove residual target substances and avoid cross-contamination.

[0046] S5. Gas Chromatography-Mass Spectrometry Detection: The target component after thermal desorption is injected into the gas chromatograph for separation, and then detected by the mass spectrometer. The retention time and response value of the target analyte and internal standard are recorded.

[0047] Gas chromatography separation: An Agilent 8890 / 5977B gas chromatograph-mass spectrometer was used, with a DB-624 column (60m×250μm×1.4μm); the injection port temperature was 220℃, the split ratio was 60:1; the temperature program was: 38℃ for 1.8 min, then increased to 120℃ at 10℃ / min, then increased to 240℃ at 15℃ / min and held for 6 min; the column flow rate was 1.0 mL / min.

[0048] Mass spectrometry detection: ion source temperature 230℃, transfer line temperature 250℃, quadrupole temperature 150℃; ion source electron energy 70eV; mass scan range 35~270 amu; data acquisition mode is full scan mode, recording the retention time of the target analyte, quantitative ion and qualitative ion response values.

[0049] S6. Qualitative and quantitative analysis: Qualitative analysis is performed by comparing with standard mass spectra and matching retention times. A standard curve is established with the ratio of the content of the target analyte to the internal standard as the abscissa and the ratio of the response value as the ordinate. The content of hexamethyldisiloxane in the soil is quantitatively calculated using the internal standard method.

[0050] Qualitative analysis: The qualitative analysis was performed by comparing the retention time of the target analyte with that of hexamethyldisiloxane in the standard solution (deviation ≤ ±0.05 min) and combining the results with the standard mass spectrum (similarity ≥ 90%).

[0051] Quantitative analysis: The concentration of hexamethyldisiloxane in the sample was calculated based on the linear equation of the standard curve. Combined with the sample moisture content and sampling amount, the content of hexamethyldisiloxane in the soil was calculated using the following formula:

[0052]

[0053] Where C represents the content of hexamethyldisiloxane in the soil (μg / kg). V represents the concentration (μg / L) obtained from the standard curve, and V represents the volume of the sample solution (L). The dilution factor is m, the sample mass (g), and w is the sample moisture content (%).

[0054] S7. Data Validation: Quality control of test results is carried out through precision experiments, recovery rate experiments, and detection limit validation.

[0055] Precision verification: Six parallel measurements were performed on the same soil sample, and the relative standard deviation (RSD) was calculated. An RSD ≤ 3.6% was considered acceptable.

[0056] Accuracy verification: Through spiked recovery experiments, hexamethyldisiloxane standard solutions of different concentrations were added to blank soil or sediment samples, and the recovery rate was determined. A recovery rate within the range of 87.0% to 115% is considered acceptable.

[0057] Detection limit validation: For the low concentration standard solution, 7 parallel determinations were performed at 2.0 μg / L, the standard deviation (S) was calculated, and the detection limit was calculated according to the method MDL=S×t (n-1,0.99) (t value is 3.143) to ensure that the detection limit is ≤0.5 μg / kg.

[0058] The method for determining the moisture content in step S2 is as follows: Take 5g of sample and dry it at 105℃ for at least 6 hours, then calculate the moisture content using the following formula:

[0059]

[0060] Where W represents the moisture content (%). The mass of the sample before drying (g) is given. The value is the mass (g) of the dried sample, and the calculation result is accurate to 0.1%.

[0061] The operating conditions of the purge trap in step S4 are as follows: purge flow rate 40 mL / min, purge temperature 20℃, purge time 11 min, dry purge time 2 min, pre-desorption temperature 245℃, desorption temperature 250℃, desorption time 2 min, baking temperature 280℃, and baking time 10 min.

[0062] The operating conditions of the gas chromatograph in step S5 are as follows: column is DB-624, injection port temperature is 220℃, split ratio is 60:1, temperature program is as follows: initial temperature 38℃ held for 1.8 min, temperature increased to 120℃ at 10℃ / min, then temperature increased to 240℃ at 15℃ / min held for 6 min, column flow rate is 1.0 mL / min.

[0063] The operating conditions of the mass spectrometer in step S5 are as follows: ion source temperature 230℃, transfer line temperature 250℃, quadrupole temperature 150℃, ion source electron energy 70eV, mass scan range 35~270amu, and data acquisition mode is full scan mode.

[0064] In step S3, the surrogate standard solution is a mixed solution of three surrogates in methanol, the internal standard solution is a mixed solution of three internal standards in methanol, and the linear equation of the standard curve is y = 0.257506x + 0.002044, with a linear correlation coefficient R ≥ 0.9998.

[0065] In step S7, the method detection limit was 0.5 μg / kg, the determination limit was 2.0 μg / kg, the recovery rate of spiked soil samples was 90.0%–111%, the recovery rate of spiked sediment samples was 87.0%–115%, and the relative standard deviation was ≤3.6%.

[0066] In step S1, a portable volatile organic compound detector can be used for on-site preliminary screening during sampling. The sample bottle must be sealed immediately after sampling to avoid loss due to volatilization of the target compound.

[0067] Sample pretreatment requires no complicated extraction or purification steps. Purge and trap combined with chromatography-mass spectrometry enables automated detection, with a single sample detection cycle of ≤30 minutes, meeting the needs for rapid detection of large batches of samples.

[0068] By optimizing the purge-and-trap parameters and mass spectrometry detection conditions, the method achieves a detection limit as low as 0.5 μg / kg and a quantification limit of 2.0 μg / kg, accurately detecting hexamethyldisiloxane in low-concentration polluted soil. The internal standard method is used for quantification, effectively eliminating matrix interference and instrument fluctuations. The linear correlation coefficient R of the standard curve is ≥0.9998. The spiked recoveries for soil samples are 90.0%–111%, and for sediment samples, they are 87.0%–115%. The detection results are reliable and applicable to the detection of different types of soil and sediment samples. The instrument is standard laboratory equipment, easy to operate, and readily applicable. By optimizing sample preservation conditions and instrument parameters, the method precision RSD is ≤3.6%, and the detection results show good stability, meeting the quality control requirements for environmental monitoring.

[0069] The above description of the embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A rapid detection method for determining hexamethyldisiloxane in soil, characterized in that, Includes the following steps: S1. Sample collection and preservation: Soil samples were collected in accordance with HJ / T 166. Three parallel samples were collected using 40mL brown sample bottles. During sampling, an appropriate amount of sample was collected into the sample bottle using a sampler. The sample bottle was quickly cleaned of any sample adhering to the threads and outer surface of the sample bottle. The sample bottle was sealed and transported to the laboratory under refrigeration. The sample bottle was stored below 4℃ and protected from light. The analysis was completed within 7 days. S2. Sample pretreatment: Take 5g of soil sample to determine the moisture content; weigh and record the weight of the purge bottle containing the sample and place it on the purge collection device for testing. S3. Preparation of standard curve: Using methanol as solvent, prepare a series of hexamethyldisiloxane standard solutions with concentration gradients of 5, 10, 20, 50, 100, and 400 μg / L. Add substitute standard solutions and internal standard solutions to each standard solution to make the internal standard concentration 50 μg / L. S4. Purge and trap treatment: Place the weighed 40mL purge bottle containing the sample on the fully automatic purge and trap device, purge and enrich with high-purity nitrogen, and obtain the target component after thermal desorption. S5. Gas Chromatography-Mass Spectrometry Detection: The target component after thermal desorption is injected into the gas chromatograph for separation, and then detected by the mass spectrometer. The retention time and response value of the target analyte and internal standard are recorded. S6. Qualitative and quantitative analysis: Qualitative analysis is performed by comparing with standard mass spectra and matching retention times. A standard curve is established with the ratio of the content of the target analyte to the internal standard as the abscissa and the ratio of the response value as the ordinate. The content of hexamethyldisiloxane in the soil is quantitatively calculated using the internal standard method. S7. Data Validation: Quality control of test results is carried out through precision experiments, recovery rate experiments, and detection limit validation.

2. The rapid detection method for determining hexamethyldisiloxane in soil according to claim 1, characterized in that, The method for determining the moisture content in step S2 is as follows: Take 5g (accurate to 0.01g) of sample and dry it at (105±5)℃ for at least 6h. Calculate the moisture content w (%) of the sample by dividing the difference in sample mass before and after drying by the mass of the sample before drying and then multiplying by 100, accurate to 0.1%.

3. The rapid detection method for determining hexamethyldisiloxane in soil according to claim 2, characterized in that, The operating conditions of the purge trap in step S4 are as follows: purge flow rate 40 mL / min, purge temperature 20℃, purge time 11 min, dry purge time 2 min, pre-desorption temperature 245℃, desorption temperature 250℃, desorption time 2 min, baking temperature 280℃, baking time 10 min.

4. The rapid detection method for determining hexamethyldisiloxane in soil according to claim 3, characterized in that, The operating conditions of the gas chromatograph in step S5 are as follows: the column is DB-624, the injection port temperature is 220℃, the split ratio is 60:1, the temperature program is as follows: start at 38℃ and hold for 1.8 min, increase to 120℃ at 10℃ / min, then increase to 240℃ at 15℃ / min and hold for 6 min, and the column flow rate is 1.0 mL / min.

5. The rapid detection method for determining hexamethyldisiloxane in soil according to claim 4, characterized in that, The operating conditions of the mass spectrometer in step S5 are as follows: ion source temperature 230℃, transfer line temperature 250℃, quadrupole temperature 150℃, ion source electron energy 70eV, mass scan range 35~270amu, and data acquisition mode is full scan mode.

6. The rapid detection method for determining hexamethyldisiloxane in soil according to claim 5, characterized in that, In step S3, the substitute standard solution is a mixed solution of three substitutes in methanol, and the internal standard solution is a mixed standard solution of three internal standards in methanol.

7. The rapid detection method for determining hexamethyldisiloxane in soil according to claim 6, characterized in that, In step S7, the method detection limit is 0.5 μg / kg, the lower limit of determination is 2.0 μg / kg, the spiked recovery rate of soil samples is 90.0%~111%, the spiked recovery rate of sediment samples is 87.0%~115%, and the relative standard deviation is ≤3.6%.

8. The rapid detection method for determining hexamethyldisiloxane in soil according to claim 7, characterized in that, In step S1, a portable volatile organic compound detector can be used for on-site preliminary screening during sampling. The sample bottle must be sealed immediately after sampling to avoid loss due to volatilization of the target substance.

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