The simplest solid phase extraction can be done manually, that is, a syringe is connected to the upper end, and the liquid in the extraction column is squeezed out of the extraction column through the squeeze of the syringe. In addition, a positive or negative pressure solid phase extraction device can also be used to perform solid phase extraction operations on batch samples.
With the development of science and technology and the increase in the number of samples, more and more analytical laboratories have begun to use automatic solid phase extraction instruments, especially multi-channel solid phase extraction instruments to process batches of samples. After selecting the extraction column, the extraction process is carried out in four steps:
Step 1: Precondition the extraction cartridges. Before extracting the sample, in order to wet the solid phase extraction packing, flush the tube with a full tube of solvent. Reversed-phase silica gel and non-polar adsorbent media are usually pretreated with water-soluble organic solvents such as methanol, and then water or buffer solution. Methanol wets the surface of the adsorbent and penetrates the bonded alkyl phase to allow water to wet the silica surface more effectively.
Sometimes the pre-treatment solvent is used before methanol and solvents are usually the same as the elution solvents, to eliminate impurities on the SPE tube and their interference with the analyte or the impurities may only be dissolved in the strong elution solvent.
Normal phase type solid phase extraction silica gel and polar adsorbent media are usually pretreated with the organic solvent where the sample is located. The ion exchange packing will be used for samples in non-polar organic solvents, which are pretreated with 3-5ml of deionized water or low concentration ion buffer solution.
In order to keep the solid phase extraction packing wet from pretreatment to sample addition, allow approximately 1 ml of pretreatment solvent on the surface of the tube filter or extraction sheet. If the sample is introduced into the solid phase extraction tube from a liquid storage tube or filter tube, add 0.5 ml of the final pretreatment solvent to the 1 ml solid phase extraction tube, if it is 2 ml to 3 ml extraction column, more add 4 liters to 6 ml tube and so on.
This is to ensure that the extraction column is wet before the sample is added. If the packing in the extraction column is dry before the sample is added, repeat the pretreatment process. Rinse the buffer salts in the column with water, before reintroducing the organic solvent.
Step 2: Add the sample. Load the sample into the extraction column. At this time, the packing in the solid phase extraction cartridge will adsorb the compound of interest in the sample or the impurities in the sample.
Step 3: Rinse the packing. Use a compound rinse solution that is strong enough to wash out impurities but weak enough to retain the compound of interest to rinse impurities.
Step 4: Elute the compound of interest. The compound adsorbed on the extraction column is eluted into the solution with a solvent.