Let us suppose there is a batch of samples which is calculated by six to twelve. The situation is that one analyst can complete the QuEChERS pretreatment in forty minutes. And the QuEChERS pretreatment only includes two steps: the extraction and the purification. People can improve the extraction efficiency of the target substance when doing simple optimization in the QuEChERS pretreatment.
The first step is the extraction. The components of the extraction salt package are magnesium sulfate, sodium chloride, and other buffer salts. The salting-out effect can separate water layer from acetonitrile liquid. In the process of extraction, the extraction efficiency of different pesticides can be affected by adjusting different PH. For example, some alkali-sensitive pesticides will be relatively stable in the acidic system, so people should take reagent kits with buffer salts such as AOAC and EN.
The second step is purification. The sample will be stratified after high-speed centrifugation. The top layer is the acetonitrile layer which dissolves the target substance. A certain amount of acetonitrile layer solution is taken into the centrifugal tube which is pre-added with the dispersive purification adsorbent.
The purification tube of food, for example, contains a certain proportion of PSA, MgSO4 and so on. If the sample contains a large amount of fat, we can increase the content of C18. If the samples contain a large number of pigments, the addition of GCB can be considered. The aim of optimization is high recovery.
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