How to deal with the unsatisfactory effect of solid phase ex

Solid phase extraction (SPE) is a sample pretreatment method based on chromatographic separation, which is widely used in recent years. How to improve the effect of SPE purification? It is suggested to consider the following points:
1. Improvement of purification mode
Generally speaking, the purification effect of target compound retention mode is better than that of impurity retention mode. If the project under analysis is for a certain kind of compound analysis, it is better to adopt the purification mode of retaining target compound; for a simple example, the analysis of Carbendazim and thiabendazole (a kind of alkaline pesticide) in vegetables can be specific by using cation exchange column However, the use of normal phase adsorbent or graphitized carbon black can only remove the main interfering substances, and there are still many interfering substances left.
In addition, if more than one SPE column can be used for the purification of target compounds, the adsorbent with good selectivity should be selected; in terms of selectivity, ion exchange > normal phase > reverse phase.
2. Optimization of eluent and eluent
For the reverse phase mode and normal phase mode, the elution intensity of eluent should be increased and the elution intensity should be decreased without affecting the recovery rate.
For the reverse mode, the aqueous solution of the target compound can be loaded, and then eluted with 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100% methanol aqueous solution in turn. The eluent is collected for analysis, and the elution curve is established to find out the solvent system when the target compound is eluted. The methanol content in the eluent should be slightly lower than that when the target compound is just eluted When pure methanol can not elute the target compound, the elution curve of methanol methyl tert butyl ether mixed solution should be tested; for some ionic compounds which are neither soluble in water nor methanol, acid or alkali can be added into the solvent system.
For the normal phase system, the n-hexane solution of the target compound can be loaded, and then eluted with 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% n-hexane methyl tert butyl ether solution. The eluent was collected for analysis, and the elution curve was established to find out the solvent system when the target compound was eluted The content of MTBE in the eluent should be slightly higher than that in the solvent system when the target compound is just eluted.
3. Reasonable treatment of SPE column
There may be a small amount of interferents in the adsorbent of SPE column, which can be avoided by effective activation. The solvent system with strong elution intensity in the whole operation should be selected as the activation solution; in the reverse phase mode, 0% - 100% methanol aqueous solution is mainly involved from the sample solution to the eluent, so the pure methanol should be selected as the activation solution, when the target compound needs to use methanol methyl tert butyl In normal phase mode, 0% - 100% n-hexane methyl tert butyl ether solution is involved from sample solution to eluent, so pure MTBE should be selected as activation solution.
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