Take primary secondary ammonia (PSA) in a dispersed solid phase extractant to remove fatty acids, graphitize carbon black, to remove planar macromolecules (such as pigments, oils, fats, non-polar compounds) and reduce the amount of residual water in the extract with anhydrous magnesium sulfate. After mixing and centrifuging, the supernatant is taken for analysis.
Sample preparation technology and instrumental analysis technology
If only the chromatographic instrument is used for qualitative and quantitative analysis, it must be fully purified in the pre-treatment. For example, conventional techniques can achieve better results, however, the entire pre-processing process is cumbersome and the processing steps are complicated. The more steps, the more the target loss, the more errors. For some pesticides, the recovery is not ideal, a large amount of organic solvent is used, and the work efficiency is not high, and the operator’s health is at risk.
If a simpler pre-processing technique, such as the QuEChERS method, is used, the whole process is very simple, with fewer steps, and only two centrifugations are required. It not only saves organic solvents but also improves work efficiency. The safety of the inspectors is guaranteed. However, the purification effect is not ideal, and a large number of co-extracted materials are highly interfering. At this time, it requires late instrument analysis with strong anti-interference ability, high sensitivity, and low detection limits.
If it is a chromatographic instrument, the target is enough to be covered by the co-existing interference, and the detection requirements are not met. At this time, the use of chromatography-tandem multi-stage mass spectrometry meets this requirement. The simple and easy pre-processing, and the fast economy has become a trend. QuEChERS method + MS / MS, LS-MS / MS mode with high specificity and high sensitivity, will inevitably become the mainstream detection method.