NEWS
21
2025
-
05
Solid-phase extraction is used for the determination of pyridine herbicide residues in Chinese cabbage
1. Preface
Pyridine herbicides such as chlorofluoropyloxyacetic acid and fluthiazine are important for the development and synthesis of various highly active herbicide varieties
It is widely used as raw materials and intermediates, and is also directly developed and applied as an active herbicide. It is mainly used to control annual and perennial broadleaf weeds. After being sprayed on the stems and leaves, it is absorbed by the leaves and accumulates in the meristematic tissues of the leaves and roots, which inhibits plant growth, causes the plants to wither and die. In this paper, experiments were conducted on the purification link of the entire detection process of pyridine herbicides in Chinese cabbage using the solid-phase extraction instrument JH-GX12W.
2 Instruments and reagents
2.1 Instruments
JH-GX12W solid-phase extraction instrument, liquid chromatography-mass spectrometry/mass spectrometer, crusher, centrifuge, vortex mixer, nitrogen evaporator, 0.22um organic phase type microporous filter membrane
2.2 Reagents and Consumables
Acetonitrile, sodium chloride, C18 solid-phase extraction column (3ml, filler 500mg)
3 Experimental Methods
3.1 Experimental Procedures
3.1.1 Sampling
The cabbage samples were processed into a paste with a tissue homogenizer and mixed well for later use.
3.1.2 Extraction
Weigh 5g (accurate to 0.01g) of the sample into a 100mL centrifuge tube and add an appropriate amount of deionized water to soak for a moment. Join
Mix 10mL of acetonitrile on a vortex mixer for 3 minutes, then centrifuge at 5000r/min for 5 minutes. Transfer the supernatant to another centrifuge tube. The above extraction process was repeated with 10mL and 5mL of acetonitrile respectively, and the extracts were combined. Add an appropriate amount of sodium chloride, shake thoroughly, and centrifuge at 5000r/min for 3 minutes. Take the upper 5mL of acetonitrile extract into a 10mL sample tube, and concentrate it by nitrogen blowing at 40 ° C to approximately 2mL. Mix thoroughly and prepare for purification.
(Extract)
Process | Reagent name | Dosage | Speed | Waiting time | Air booster | Frequency |
Activation | Acetonitrile | 5mL | 3mL/min | 0s | 2mL | 1 |
Activation | Acetonitrile | 2mL | 3mL/min | 0s | 2mL | 1 |
Rinse and sample | Acetonitrile | 2mL | 60mL/min | 5s | 3mL | 2 |
Elution | Acetonitrile | 4mL | 3mL/min | 5s | 5mL | 1 |
The collected eluent was blown with a nitrogen flow at 40℃ until it was nearly dry. Dilute with 0.1% formic acid - methanol (50+50) to 1mL.
After the vortex is mixed evenly, it passes through a 0.22um microporous filter membrane for liquid chromatography-mass spectrometry/mass spectrometry analysis and is ready for use.
3.1.4 Liquid Chromatography determination conditions
Chromatographic column: ACQUITY BEH C18 chromatographic column, 50m* 2.1mm (inner diameter), film thickness 1.7um, or equivalent; Column temperature: 40℃
Flow rate: 0.3mL/min \ nInjection volume: 20 μ l
The mobile phase and gradient elution conditions are shown in the following table:
3.1.5 Mass spectrometry determination conditions
Ionization mode: Electrospray ionization positive ion mode (ESI+) Resolution: Resolution per unit mass
Capillary voltage (kv) : 3.00 Source temperature (℃) : 105
Solvent removal temperature (℃) : 350 Solvent removal gas flow rate (L/hr) : 750
Monitoring method: Multi-response monitoring (MRM).
3.1.6 Chromatographic determination and Confirmation
The retention time of the substance to be tested in the sample and the standard solution of the mixed matrix was determined according to the above conditions, and the deviation between the retention time of the substance to be tested in the sample and that of the standard solution of the matrix was within ±2.5%. If the relative abundance of qualitative ion pairs is consistent with that of the standard solution of the mixed matrix with the same concentration, and the deviation of relative abundance does not exceed the provisions of the following table, it can be determined that the corresponding analyte exists in the sample. Under the optimal working conditions of the instrument, inject the matrix mixed standard working solution, and draw the standard working curve with the peak area as the vertical coordinate and the concentration of the matrix mixed working solution as the horizontal coordinate. Use the standard working curve to quantify the sample. The response values of the analyte in the sample solution should all be within the linear range determined by the instrument.
4 Results and Discussion
4.1 The national standard requires that the flow rate throughout the extraction and purification process should not exceed 1 drop per second.
4.2 Start collecting all the effluent, approximately 10mL, when loading the sample.
4.3 The process of purifying the residual amount of pyridine herbicides in Chinese cabbage by solid-phase extraction is automated, reducing the consumption of human labor. The organic solvents used in the experiment are sealed, which reduces the harm to the human body. Moreover, the instrument can precisely control the flow rate of solvents for activation, sample loading, elution, etc., making the sample purification more thorough.
References
[1] GB 23200.36-2016 National Food Safety Standard - Determination of Residues of chlorofluoropyloxyacetic acid, fluthiazine, fluthiazine Hydrazone and thiazole Nicotinic Acid Herbicides in Plant-based Foods - Liquid Chromatography-Mass Spectrometry/Mass Spectrometry
Precautions
The 5mL upper acetonitrile layer was directly placed into the sample tube for concentration, avoiding sample loss during sample transfer.
After loading the sample, the sample tube should be rinsed twice. A rinsing speed of 60mL/min can achieve spray rinsing, thoroughly washing off the residual sample solution on the tube wall before passing through the column to prevent the residual sample solution from affecting the subsequent test results.
3. During the activation process, a smaller air booster is set to ensure that the column remains moist during sample loading and to enhance the purification efficiency.
4. When eluting the target substance, appropriately increase the air boost of the instrument to ensure that all the eluent remaining in the column is completely eluted.
5. When toxic and harmful reagents are used in experiments, they should be conducted in a fume hood, and at the same time, the experimenters must take proper protective measures.
Keyword:
Solid-phase extraction is used for the determination of pyridine herbicide residues in Chinese cabbage,Solid-phase extraction,Chinese cabbage, pyridine herbicide residues
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