A sample pretreatment method and detection method for determining multiple pesticide residues in Dendrobium officinale
A sample pretreatment and pesticide residue technology, which is applied to the sample pretreatment method and detection field of determining various pesticide residues in Dendrobium candidum, can solve the problem of large amount of adsorbent, lower pesticide recovery rate, and unsatisfactory removal of impurities And other issues
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Embodiment 1
[0075] Linear dependency verification:
[0076] Verify the linear correlation of each pesticide within the concentration range of 2-200ppb, the specific method is as follows:
[0077] Using the fresh stems of Dendrobium officinale without pesticide residues as raw materials, the matrix standard solution was prepared according to the following method:
[0078] After homogenizing the fresh stems of Dendrobium candidum, take 2 g of the homogenized product and mix it with 15 mL of acetonitrile-water solution (the volume ratio of acetonitrile and water is 2:1), shake at room temperature for 10 min at 5000 rpm, and then add 6 g of anhydrous sulfuric acid Magnesium and 1.5g sodium chloride, continue to shake at room temperature at 5000rpm for 5min, then centrifuge at 4000rpm for 10min, take out the supernatant as the extract;
[0079] Take 1.2 mL of the extract, mix it with 5 mg of graphitized multi-walled carbon nanotubes, vortex at 5000 rpm for 1 min, then centrifuge at 5000 rpm f...
Embodiment 2
[0090] Detection of matrix effects:
[0091] Using acetonitrile as a solvent, prepare the standard solutions of different pesticides with a concentration of 2, 5, 20, 50, 100 and 200ppb, and carry out high performance liquid chromatography-mass spectrometry analysis according to the analysis method in Example 1, and fit the linear solvent standard Curve, the slope of the linear matrix standard curve obtained in Example 1 is divided by the slope of the linear solvent standard curve to obtain the matrix effect (ME). The results are shown in Table 3.
[0092] It can be seen from Table 3 that the matrix effect (ME) value between 0.8 and 1.2 is considered as no matrix effect. When ME is greater than 1.2, it is regarded as a matrix enhancement effect. When ME is less than 0.8, it is regarded as matrix inhibition effect. It can be seen from Table 3 that there are 66 kinds of pesticides in fresh stems with a matrix effect of 80-120%. There are 64 pesticides with a matrix effect of ...
Embodiment 3
[0099] Accuracy and Precision Determination:
[0100] The recoveries of 76 target compounds were detected at two different spiked concentrations (0.02mg / kg and 0.2mg / kg), and the experiment was repeated 5 times for each concentration. The specific process is:
[0101] After homogenizing the fresh stems of Dendrobium candidum, take 2 g of the homogenized product and mix it with 15 mL of acetonitrile-water solution (the volume ratio of acetonitrile and water is 2:1), shake at room temperature for 10 min at 5000 rpm, and then add 6 g of anhydrous sulfuric acid Magnesium and 1.5g sodium chloride, continue to shake at room temperature at 5000rpm for 5min, then centrifuge at 4000rpm for 10min, take out the supernatant as the extract;
[0102] Take 1.2 mL of the extract, mix it with 5 mg of graphitized multi-walled carbon nanotubes, vortex at 5000 rpm for 1 min, then centrifuge at 5000 rpm for 10 min, and pass the supernatant through a microporous membrane with a pore size of 0.22 μ...
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