4 Tips on the Choice of SPE Cartridge

Before talking about the choice of SPE cartridge, HAWACH will discuss the SPE cartridge and its capacity first.

About the SPE cartridge and its capacity

SPE cartridge is a sample pretreatment equipment developed from chromatography columns for extraction, separation, and concentration. It is mainly used in sample pretreatment of target compounds in various food, agricultural, and livestock products, environmental samples, biological samples, etc.

The capacity of the SPE cartridge refers to the adsorption capacity of the cartridge packing. For an SPE cartridge based on silica gel, its capacity is generally 1~5 mg/100 mg, that is, the cartridge capacity is 1%~5% of the mass of the packing. The bonded silica gel ion exchange adsorbent packing capacity is meq/g, that is, the capacity of each gram of packing is X milliequivalents. The capacity of this type of packing is usually 0.5 to 1.5 meq/g.

C18A SPE Cartridges

How to choose the SPE cartridge

Choosing the right Solid Phase Extraction (SPE) cartridge is crucial for achieving efficient and selective sample preparation in chromatographic analyses. Here are four tips to guide you in the selection of SPE cartridges:

Understand Your Analytes:

Before choosing an SPE cartridge, thoroughly understand the properties of the analytes you are extracting. Consider factors such as polarity, charge, and solubility. Different SPE sorbent chemistries are designed to interact selectively with specific types of analytes. For example:
Reversed-Phase (RP) Sorbents (e.g., C18): Suitable for non-polar and moderately polar compounds.
Normal-Phase Sorbents (e.g., Silica): Effective for polar compounds.
Ion-Exchange Sorbents: Useful for separating charged compounds.

Evaluate Sample Matrix:

The nature of your sample matrix plays a significant role in choosing the right SPE cartridge. Biological fluids, environmental samples, and complex mixtures may require different sorbent chemistries. Ensure that the cartridge you select can effectively remove interfering substances from your sample matrix.

Consider Loading Capacity:

Evaluate the loading capacity of the SPE cartridge to ensure it can handle the volume of your sample. Overloading the cartridge can lead to reduced extraction efficiency and compromised results. Choose a cartridge with an appropriate bed mass or loading capacity based on your sample size.

Assess Particle Size:

The particle size of the sorbent in the SPE cartridge affects the surface area and, consequently, the extraction efficiency. Smaller particle sizes provide higher surface area but may result in increased backpressure during the extraction process. Consider the balance between particle size and backpressure to ensure optimal performance.

In short, the selection must be made according to the nature of the sample and the solvent background. Generally speaking, there is no uniform regulation about what solvent to be used for the activation and elution of the solid phase extraction packing. Please refer to the national standard, pharmacopeia, or validated method based on your analysis.

1. Activation: There are two purposes for the activation of the SPE cartridge, one is to infiltrate the packing so that the sample solution can flow through it; the second purpose is to clean the interfering impurities and solvent residues on the SPE cartridge.

2. Sample loading: Let the sample solution flow through the solid phase extraction column to allow the packing to adsorb the target substance. Generally, the flow rate should not be too fast, otherwise, the adsorption is not complete and the recovery rate will be below.

3. Washing: It is necessary to choose a suitable solvent, which will not wash off the target product adsorbed on the SPE cartridge packing, but also wash away some interfering impurities. This choice is also based on existing methods and there is no uniform standard.

4. Elution: Choose a suitable solvent to elute the target substance adsorbed on the SPE cartridge packing (most of the time you need to use a test tube to collect). This solvent is also determined according to the specific experimental method and cannot be uniformly specified.

If the above cannot clear your doubts, welcome to contact HAWACH for more, who has years of experimental experience.