How to Use the SPE Cartridge(Reversed Phase, Normal Phase, and Ion Exchange Cartridge)?

Solid phase extraction cartridge
The solid phase extraction column or cartridge is a sample pretreatment device for extraction, separation, and concentration developed from a chromatography column. Most of the common SPE cartridges are syringe-type devices made of polyethylene. The device is equipped with two plugs made of polypropylene or glass fiber, and a certain amount of chromatographic adsorbent (filler) is filled between the two plugs. In recent years, the application of solid phase extraction cartridges has been rapidly developed and has been widely used in food, environmental, pharmaceutical, and other industries, becoming one of the effective means of sample pretreatment and purification.

In the process of solid phase extraction, the attractive force of the solid compared to the analyte is greater than the sample mother liquor. When the sample passes through the SPE column, the analyte is adsorbed on the solid surface, and other components pass through the column with the sample mother liquor and then use an appropriate solvent to remove the elutes.

SPE cartridge can be divided into four types according to its principle: reverse, normal, adsorption, and ion exchange. The normal phase cartridge, it extracts polar samples from non-polar matrices, and the reversed phase extracts non-polar samples from polar matrices, such as Normal Phase Diol SPE Cartridge. The Ion exchange cartridge extracts charged samples. For the reverse, normal, and adsorption type, the mass of the extracted sample does not exceed 5% of the amount of packing in the column. That is to say, if you use a 100 mg/1ml solid phase extraction column, the analytical substance does not exceed 5 mg, such as Reversed Phase C18 SPE Cartridges. For the Ion exchange process, we must consider the capacity of ion exchange:SCX SPE Cartridges, SAX SPE Cartridges have an adsorbent capacity of 0.2 meq/g.

Please choose the appropriate cartridge size based on the sample volume. Check the following table for better understanding. If you still cannot decide, please contact HAWACH team directly.

4 Steps to Use SPE Cartridges

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: Pre-treat the extraction column.
As we know, the SPE cartridge needs to be pretreated with a suitable solvent to achieve good reproducibility and a high recovery rate by removing the possible packing impurities. Another purpose for the SPE cartridge pretreatment is to solvate the filler and improve the SPE reproducibility.

Before extracting the sample, flush the tube with a full tube of solvent to wet the solid phase extraction column packing. Reversed-phase type silica gel and non-polar adsorbent media are usually pretreated with water-soluble organic solvents such as methanol, and then use water or buffer solution. Methanol wets the surface of the adsorbent and penetrates the bonded alkyl phase to allow water to wet the surface of the silica gel more effectively.

Sometimes the pre-pretreatment solvent is used before methanol. These solvents are usually the same as the elution solvents, which are used to eliminate impurities on the solid phase extraction tube and their interference with the analyte and it is also possible that the impurities are only soluble in the strong elution solvent.

Pretreat the SPE normal phase silica gel and polar adsorbent media with the organic solvent. For non-polar organic solvents, Ion exchange packing will be used. Pretreat it with a low-concentration ion buffer solution or 3-5ml of deionized water. In order to keep the solid phase extraction packing moist from pretreatment to sample addition, allow approximately 1 ml of pretreatment solvent on the surface of the frit or extraction sheet.

When introducing the sample from a filter tube or a liquid storage tube into an SPE tube, 0.5 ml final pretreatment solvent will be added to the 1 ml solid phase extraction tube; if it is a 2 ml to 3 ml extraction column, add 4 ml to the 6 ml into the tube. By doing so, it aims to keep the extraction column wet before the sample is added. If becomes dry, repeat the above process. Before reintroducing the organic solvent, rinse the salt of the buffer solution in the column with water.

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 samples.
Load the sample into the extraction column and the cartridge packing will absorb the sample impurities or the compound of interest. In this way, when the sample flows out, the selected compounds (including impurities) are left on the extraction column.

Step 3: Rinse the filler.
Use a wash solution that is able to elute impurities but also can retain the compound of interest to wash out impurities.

Step 4: Elute the compound of interest.
The compound adsorbed on the extraction column is eluted in the solution with a solvent.