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

Q. Is it necessary to filter with 0.45um or 0.22um filter after purification? If it is used, is there any adsorption on the pesticide? Is it not harmful to the column?

A: This question depends on personal thoughts. The membrane will definitely have a little protection for the column. We have been using the membrane, and there is no obvious adsorption of the pesticide on the membrane.

Q. If it is a sample with less water content, such as tea, I am now weighing 3.75g of tea and adding 11.25g of water to make the water content high. Is this reasonable?

A: For dry samples, especially tea-based matrices, I generally take the reduction of sample weight and water soaking. We have been doing this.

Q. Is the graphitized carbon black powdery or granulated? Which type of effect is better when the sample is pretreated (especially to remove the pigment)?

A: At present, the graphitized carbon we use is fine particles with a particle size between 120 and 400 mesh. In pre-treatment, if matrix-dispersed solid phase extraction is used, the fine-grain effect of the particles should be better. In the case of conventional SPE, the particles are too fine to cause too much back pressure, which usually results in the sample not passing. At present, the average particle size is between 120-400 mesh.