HAWACH to Talk About the Modified QuEChERS With Purification Optimization

Optimize the purification process
PSA, GCB, C18, and other adsorbents have their own advantages and disadvantages. PSA is alkaline because it contains 2 amine groups, which will affect the recovery rate of acid pesticides such as folpet, and bacteriostatic, and GCB will adsorb flat structural compounds and reduce the recovery rate of pesticides such as hexachlorobenzene and thiabendazole. C18 will adsorb some pesticides such as diazinon and tebuconazole, reducing its recovery rate.

In order to improve the recovery rate of these susceptible pesticides, the researchers tested the combination of these three adsorbents in different proportions, and also tried a variety of different materials, and achieved satisfactory results. The purification optimization includes adjusting the content of PSA, GCB, C18, and other adsorbents according to different substrates and using other adsorbent materials to purify the substrate.

1. Adjust the content of the adsorbent and other experimental conditions
The researchers used statistical software to examine the influencing factors such as solvent volume, buffer salt, and the content of various adsorbents from a theoretical point of view and obtained variables that have a greater correlation with the results, and then used the optimization software to fit a curve to calculate the best solution.
Manav et al. used Plackett-Burman experimental design (PBD) to screen for variables such as acetonitrile volume, formic acid content, sodium chloride, anhydrous sodium sulfate, sodium acetate, diatomaceous earth, anhydrous magnesium sulfate, and quality of C18. The Behnken design (BBD) method is optimized to determine the best combination of extraction and purification effects.

The results showed that when measuring 25 pesticide residues in dairy products, the sampling volume was 10g, 10 ml of acetonitrile (containing 1% formic acid) was added, and extracted with 5.7g of sodium chloride, 6g of anhydrous sodium sulfate, and 4.2g of sodium acetate. After shaking and centrifugation, take 7 ml of supernatant and purify with 0.5 g of diatomaceous earth, 300mg of anhydrous magnesium sulfate, and 150mg of C18, and use GC-MS to obtain satisfactory results.

Viera et al. used a full factorial design to screen: 3g samples were extracted with 10 ml acetonitrile containing 5% formic acid, separated with 1.5g sodium chloride, 4g anhydrous magnesium sulfate, and 2ml were taken after shaking centrifugation. The purification of 300 mg anhydrous magnesium sulfate, 50 mg C18, and 10 mg GCB in the clear solution can obtain good results and meet EU requirements.

2. Use new materials as adsorbents
The purification process plays a very critical role in the QuEChERS method, so a large number of researchers are constantly exploring new materials as adsorbents. Some reported materials include Z-Sep, chitosan, magnetic nanoparticles (MNPs, graphene) Oxides tri-Bua-rGO, fluorinated adsorbents, phenolic resin-based activated carbon fibers (ACFs), etc. These materials have achieved good results as adsorbents in the purification process.

Moreno-González et al. determined the pesticide residues in various edible oils. In the case of using acetonitrile as the extraction solvent, the purification effect of the combination of Z-Sep Plus and C18 + PSA was compared. It was found that the former can significantly reduce the matrix effect, which is Z-Sep Plus is better at removing lipids than C18 and PSA.

The selection and use of new materials not only obtain better experimental results but also enriches the reserve of QuEChERS adsorbent materials, which provides a basis for the expansion of its scope of use and enables it to have a wider application range.