Gas chromatography-mass spectrometry method for determining dimethyl sulfate in solid waste

Abstract

The invention discloses a gas chromatography-mass spectrometry detection method for dimethyl sulfate in solid waste. The gas chromatography-mass spectrometry detection method comprises the steps of sample collection and preservation, pretreatment (preparation, extraction, concentration, purification and internal standard addition) and instrumental analysis. By optimizing extraction conditions, a purification process and chromatographic mass spectrometry parameters, high-sensitivity and high-precision detection is realized, the detection limit is 0.47 mg / kg, the lower determination limit is 1.88 mg / kg, and the method is suitable for quantitative analysis of the substance in the solid waste.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental monitoring and analysis, and particularly relates to a method for determining diethyl sulfate (Dialky Sulfate, abbreviated as DES) in solid waste based on gas chromatography-mass spectrometry (GC-MS), which is applicable to the rapid screening and quantitative analysis of DES in solid waste. Background Art

[0002] Dimethyl sulfate (CAS: 77-78-1) is a toxic organic compound, often used as a methylation reagent, and its residues in the environment pose potential risks to the ecosystem and human health. The detection of dimethyl sulfate in solid waste needs to meet the requirements of high sensitivity and high accuracy, but the existing methods have the following problems: 1. The pretreatment process is complex: The traditional extraction and purification methods are inefficient and prone to loss of the target substance; 2. The detection limit is insufficient: For low-concentration samples, the existing methods may not be able to accurately detect them; 3. The precision and correctness fluctuate: The differences in instrument conditions and operating parameters may affect the reliability of the detection results. Summary of the Invention

[0003] Object of the Invention To provide a method for detecting dimethyl sulfate in solid waste with simple operation, high sensitivity, excellent precision and correctness, meeting the requirements of environmental monitoring and industrial analysis.

[0004] Technical Solution A gas chromatography-mass spectrometry detection method for dimethyl sulfate in solid waste, comprising the following steps: Sample Collection and Preservation Collect the solid waste in a clean stoppered ground-glass brown glass bottle, seal and avoid light during transportation, and refrigerate at 4°C to prevent degradation or contamination of the target substance.

[0005] Sample Pretreatment Sample Preparation Weigh 2.0 g of the sample, add an appropriate amount of analytical grade anhydrous sodium sulfate, and dry and mix evenly until it becomes like flowing sand; if pressurized fluid extraction is used, 20-40 mesh diatomaceous earth can be used for dehydration, or the ground and sieved sample can be directly selected.

[0006] Extraction Transfer the dehydrated sample to the extraction cell, use a dichloromethane-acetone mixed solvent (volume ratio 1:1, pesticide residue grade) as the extractant, set the extraction conditions: pressure 1500 psi, temperature 120°C, adopt the 100% full extraction cell mode, statically stand at high temperature and high pressure for 5 min, and extract three times in a cycle, and collect the extract. These conditions can efficiently dissolve the target substance and reduce matrix interference.

[0007] Concentration Transfer the extract to a concentrator of a nitrogen blowing instrument and concentrate it to 1 - 2 ml at 40°C to avoid the volatilization loss of the target substance.

[0008] Purification Purify using a magnesium silicate adsorption column of 1000 mg / 6 ml: • First, rinse the column with 4 ml of pesticide - free n - hexane to remove impurities; • Add 5 ml of n - hexane to soak the column for 5 min to ensure sufficient activation of the packing; • Transfer the concentrated solution to the column, wash the concentrator tube with 1 - 2 ml of n - hexane, and add the washing solution to the column, keeping the liquid level above the packing not less than 0.5 cm; • Elute with 10 ml of dichloromethane - n - hexane mixed solvent II (volume ratio 9:1), collect all the eluate to remove polar interfering substances.

[0009] Secondary Concentration and Internal Standard Addition Concentrate the eluate by nitrogen blowing again until nearly dry, add the internal standard 1,4 - dichlorobenzene - D4 (CAS: 3855 - 82 - 1) with a concentration of 40 mg / L, make up the volume to 1.0 ml with dichloromethane, mix well and transfer to a 2 - ml sample vial for determination. The addition of the internal standard improves the quantitative accuracy.

[0010] Instrumental Analysis Gas Chromatography Conditions • Chromatographic column: SH - I - 5MS capillary chromatographic column (30 m × 0.250 mm × 0.25 μm), with both high column efficiency and an inert surface; • Injector temperature: 280°C, splitless injection, injection volume 1.0 μl, column flow rate 1.0 ml / min (constant flow mode); • Column temperature program: Hold at 40°C for 3.5 min, increase to 80°C at a rate of 10°C / min, then increase to 150°C at a rate of 6°C / min, and finally increase to 290°C at a rate of 22°C / min and hold for 5.5 min to achieve efficient separation of the target substance from the matrix.

[0011] Mass Spectrometry Conditions • Ion source: Electron impact source (EI, 70 eV), ion source temperature 230°C, interface temperature 280°C; • Solvent delay time: 5 min to avoid solvent peak interference; • Data acquisition: Full scan mode (SCAN), scan range m / z 40 - 450; • Qualitative and quantitative ions: The quantitative ion is m / z 95, and the qualitative ions are m / z 96 and m / z 45. Qualitative analysis is achieved by retention time and the abundance ratio of characteristic ions, and quantitative analysis is performed by external standard method combined with internal standard calibration.

[0012] Beneficial effects 1. High sensitivity: The method detection limit is 0.47 mg / kg, and the determination lower limit is 1.88 mg / kg, meeting the detection requirements of low-concentration samples; 2. Excellent precision: The relative standard deviation (RSD) of the spiked samples ≤ 13%, with good repeatability; 3. Accurate and reliable: The spiked recovery rate ranges from 74% to 91%, ensuring the authenticity of the detection results; 4. Efficient and convenient: The optimized pretreatment process (pressurized fluid extraction + magnesium silicate column purification) shortens the operation time and reduces human error; 5. Strong universality: Applicable to solid waste with different matrices, with good compatibility.

[0013] Figure 1 : Total ion chromatogram (TIC) of the target dimethyl sulfate, retention time 7.100 min, quantitative ion m / z 95; Figure 2 : Matching degree of dimethyl sulfate with the spectral library.

[0014] Figure 3 : Total ion chromatogram (TIC) of the internal standard 1,4-dichlorobenzene-D4, retention time 10.447 min, quantitative ion m / z 150; Figure 4 : Matching degree of 1,4-dichlorobenzene-D4 with the spectral library.

[0015] Example 1: Detection of solid waste samples 1. Sample pretreatment • Weigh 2.0 g of the solid waste sample, add 1 g of anhydrous sodium sulfate, mix evenly and transfer to the extraction cell; • Using dichloromethane-acetone (1:1) as the solvent, extract three times at 1500 psi and 120 °C for 5 min each time, and collect the extract; • Concentrate to 1 ml by nitrogen blowing, purify through a magnesium silicate column, add the internal standard after concentrating the eluate, and make up the volume to 1.0 ml.

[0016] Instrument analysis • Inject and analyze according to the above gas chromatography and mass spectrometry conditions, calculate the concentration in the sample through the standard curve (Y = 0.001190x - 0.004227, r = 0.9980), and the actual sample determination result is "ND" (not detected).

[0017] Example 2: Spike Recovery Experiment • Add 10.0 ml of 1000 mg / L dimethyl sulfate standard solution to a blank quartz sand sample and process it according to the steps in Example 1; • The spike recovery rate was measured to be 74% - 91%, and the relative standard deviation was 13% to verify the accuracy and precision of the method.

[0018] Method Validation Parameters Performance Index Results Detection Limit (mg / kg) 0.47 Lower Limit of Quantitation (mg / kg) 1.88 Precision (RSD, %) ≤13 Spike Recovery Rate (%) 74 - 91 Claim Citation This specification supports the detection methods described in Claims 1 - 6, and the specific parameters and steps are as shown above.

Claims

1. A gas chromatography - mass spectrometry detection method for dimethyl sulfate in solid waste, characterized in that, It includes the following steps: ◦ Sample collection and preservation: Collect the solid waste in a clean stoppered ground-glass brown glass bottle, seal it and avoid light during transportation, and refrigerate it at 4°C; ◦ Sample pretreatment: ◦ Sample preparation: Weigh 2.0 g of the sample, add anhydrous sodium sulfate, dry and mix evenly until it becomes like flowing sand. If pressurized fluid extraction is used, dehydrate it with diatomaceous earth or directly select the sample after grinding and sieving; ◦ Extraction: Transfer the dehydrated sample to the extraction cell, use dichloromethane-acetone mixed solvent (1:1) as the extraction solvent, under the conditions of a pressure of 1500 psi and a temperature of 120°C, adopt the 100% full extraction cell mode, statically stand at high temperature and high pressure for 5 min, cycle three times, and collect the extract; ◦ Concentration: Transfer the extract to a concentration device and concentrate it to 1 - 2 ml; ◦ Purification: Wash the magnesium silicate adsorption column with 4 ml of n-hexane, then add 5 ml of n-hexane and soak for 5 min. Transfer the concentrated solution to the column, wash the concentration tube with 1 - 2 ml of n-hexane, and add the washing solution to the column together. Keep a liquid level above the packing. Elute with 10 ml of dichloromethane-n-hexane mixed solvent II (9 + 1), and collect the eluate; ◦ Secondary concentration and internal standard addition: After concentrating the eluate, add the internal standard 1,4-dichlorobenzene-D4, and make up the volume to 1.0 ml with dichloromethane. Mix well and transfer it to a 2-ml sample bottle for determination; ◦ Instrumental analysis: ◦ Gas chromatography conditions: Use a SH - I - 5MS capillary chromatographic column (30 m × 0.250 mm × 0.25 μm), the inlet temperature is 280°C, splitless injection, the injection volume is 1.0 μl, the column flow rate is 1.0 ml / min (constant flow), and the column temperature program is: maintain at 40°C for 3.5 min, rise to 80°C at a rate of 10°C / min, then rise to 150°C at a rate of 6°C / min, and finally rise to 290°C at a rate of 22°C / min and maintain for 5.5 min; ◦ Mass spectrometry conditions: Electron impact source (EI), the ion source temperature is 230°C, the interface temperature is 280°C, the solvent delay time is 5 min, the data acquisition mode is full scan mode (SCAN), and qualitative and quantitative analysis are carried out with the quantitative ion m / z95 and qualitative ions m / z96, m / z45 of dimethyl sulfate.

2. The detection method according to claim 1, wherein, The concentration of the internal standard 1,4-dichlorobenzene-D4 is 40 mg / L.

3. The detection method according to claim 1, wherein The anhydrous sodium sulfate is of analytical reagent grade, and the n-hexane, dichloromethane, and acetone are all of pesticide residue grade.

4. The detection method according to claim 1, wherein The specification of the magnesium silicate adsorption column is 1000 mg / 6 ml.

5. The detection method according to claim 1, wherein During the sample pretreatment process, the concentration operation is carried out with a nitrogen blower.

6. The detection method according to claim 1, wherein The detection limit of the method is 0.47 mg / kg, and the determination limit is 1.88 mg / kg.

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