Frequently asked questions about QuEChERS products in experiments(part 5)

1. What kind of material is used for the extraction of the centrifuge tube? Does the centrifuge tube of the polypropylene purchased by itself have an effect on the extraction, such as adsorption of pesticides?

A: At present, the commercial QuEChERS kits are all made of polypropylene centrifuge tubes. There is no data showing that the polypropylene centrifuge tubes will adsorb pesticides, but it is better to use screw-type centrifuge tubes, so that the sealing performance will be better.

2. In the process of the first step of extraction, after adding the filler, it will release heat, and the temperature of the centrifuge tube is still quite high. Will it affect the recovery rate of the pesticide? Some pesticides appear to be sensitive to temperature.

A: The exotherm of anhydrous magnesium sulfate and water does increase the temperature of the centrifuge tube. Generally, it has been added to the salting out package after it has been extracted. After the addition, it is required to understand the violent oscillation, so that the heat can be dissipated; In the sample pulverization, dry ice is added, or the sample is pulverized and placed in a refrigerator overnight to be cooled, and then the loss can be reduced.

3. After purging the nitrogen, do you want to blow it dry? Or do you want to stay a little?

A: If you directly enter the LC-MS analysis after purification, you can use no solvent conversion; when the solvent is converted, the nitrogen is blown to near dryness, then a small amount of solvent to be converted is added, and then nitrogen is blown to near dry to constant volume.