Two factors will be considered generally when choosing the SPE cartridges, which are the selection of adsorbents and the selection of cartridge specification. The proper adsorbents will separate the interfering materials and the target substances better and satisfy the retrieving demands at the same time. And there exists upper limits of the quality of compounds adsorbed by adsorbents. Once the quality of adsorbed compounds exceeds, the target substances will pass over the SPE cartridge straightly instead of remaining in it.
The selection of adsorbents
Adsorbents should be selected according to the properties of target compounds and substrates. As to the examples, we can choose the adsorbents based on the principle that distinguishes target substances and the major interfering materials.
| Specification | Maximum sample size | Minimum elution volume |
| 50mg | 2.5mg | 125μL |
| 100mg | 5mg | 250μL |
| 150mg | 7.5mg | 375μL |
| 200mg | 10mg | 500μL |
| 500mg | 25mg | 1250μL |
| 1000mg | 50mg | 2500μL |
| Substrates | Target substances | Major Interfering Materials | SPE Cartridges |
| Soil, Sewage | hydrophobic organic pollutants | Humic substances | C18, SLC |
| Fruits, vegetables, Chinese medicine, fruits syrup | pesticide residues | Carbohydrates, pigments, organic acids, phenols | NH2、Carbon/NH2 |
| Pesticide residues with weak polarity | C18 | ||
| Alkaline drugs | PCX | ||
| Acidic drugs | PAX | ||
| Grease | Liposoluble vitamins, phospholipids, aflatoxins | fat | NH2、PSA |
The selection of cartridge specification
After choosing the proper adsorbent, we should choose the proper SPE cartridges with the best specification according to the volume of samples. And if the quality of the compounds to be measured is beyond the limit, the target substance will not be remained effectively, and the result of the elution is not good. Therefore, it is necessary to choose the proper specification.
| Specification | Maximum sample size | Minimum elution volume |
| 50mg | 2.5mg | 125μL |
| 100mg | 5mg | 250μL |
| 150mg | 7.5mg | 375μL |
| 200mg | 10mg | 500μL |
| 500mg | 25mg | 1250μL |
| 1000mg | 50mg | 2500μL |
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