Pre-treatment is the longest and most labor-intensive part of food testing. The quality of pre-treatment determines the accuracy and precision of the analysis. QuEChERS method is a kind of high-precision sample pretreatment technology because it is quick, easy, cheap, effective, rugged and safe. It uses the adsorbent filler to interact with impurities in the matrix to adsorb impurities to achieve impurity removal.
Main steps
The main step of the method is to extract the sample with acetonitrile containing 1% acetic acid, and then add anhydrous magnesium sulfate and sodium acetate to oscillate it to stratify, followed by dispersion solid-phase extraction, that is, the extract is transferred to PSA-containing adsorption.
In a centrifuge tube of magnesium sulfate, centrifuge with a Teflon-coated centrifuge tube, centrifuge the solution to an autosampler for GC/MS or LC/MS and analyze and evaluate its stability and reliability. At the same time, the method can be appropriately adjusted according to the type of analytical instrument available, the limit of detection, the range of the target pesticide, and the difference in the medium used.
Pesticide residues
Pesticide residues are a general term for all derivatives of pesticides and their toxicologically significant impurities, metabolic conversion products, and reactants that remain in organisms, agricultural products, and the environment due to the application of pesticides. The composition of agricultural products and food samples is complex.
The pesticide residue content is extremely low, generally in ppm and ppb, and there are also the influences of pesticide homologs, isomers, degradation products, metabolites, and conjugates. To remove the target simultaneous impurities, reduce chromatographic interference peaks, and avoid contamination of samples by detectors and columns, pretreatment is very important, accounting for about 70% of the workload.
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