Common Terminology for Solid Phase Extraction

Aimed Compounds:

Compounds that are intended to be separated from complex sample matrices.

Matrix:

The environment in which the target compound is placed. The matrix usually contains a large number of interferents.

Interferential Compounds: Compounds that affect the analysis of a target compound or that can cause damage to an analytical instrument, usually a generic term for all compounds in the matrix other than the target compound.

Sorbent:

A filler in a solid phase extraction column selectively extracts certain compounds from a sample solution.

Capacity:

The total mass of a compound (including target compounds and some interferents) that a certain mass of adsorbent can retain under certain conditions.

Selectivity:

The ability of an adsorbent to treat a target compound and all other sample components differently, that is, the ability to retain the target compound while excluding other components, and high selectivity for better purification.

pH:

The negative logarithm of the proton (H+) concentration in the solution. The smaller the value, the greater the concentration of protons in the solution.

pKa:

The negative logarithm of the acidic compound dissociation constant (Ka), the smaller the value, the stronger the dissociation of the acidic compound. When the pH value of the sample solution is equal to pKa, the concentration of the undissociated compound and the dissociated compound are equal.

Analysts also commonly use pKa to represent the dissociation of basic compounds, but the pKa value at this time represents the negative logarithm of the dissociation constant of the conjugate acid of the basic compound. The larger the value, the stronger the ability of the basic compound to bind protons, and the stronger the basicity.

Interaction:

The attraction or repulsive force between two chemicals (such as between a target compound and an adsorbent, between a target compound and a solvent molecule) in a specific chemical environment.

Non-Polar Interaction:

The force between a non-polar functional group on a target compound and a non-polar sorbent. This force is better reflected in a polar solvent environment, especially in a water environment. And thus also known as hydrophobic interactions, such as the interaction between phthalate compounds and C18 in aqueous environments.

Equilibrium:

Remove the activation solvent to create a suitable solvent environment for the sample. The solvent used is usually the same as the solvent of the sample solution. For the ion exchange column, if the sample is a basic compound, it is necessary to add acid if the sample is acidic. It is often necessary to add a base to the compound balance solution.

Retention:

When the sample solution passes through the adsorbent, and the force of the adsorbent and certain compounds exceeds the force of the latter and the solvent, these compounds are fixed by the adsorbent, and the process is called retention;

Washing:

After loading, some of the interferents are retained at the same time as the target compound. It is necessary to add a suitable solution to remove the interferences without affecting the retention of the target compound. Usually, the sample solvent is used for loading. Washing does not affect the recovery rate, but the solvent with higher elution intensity can remove the interference. When choosing the eluent, it is necessary to find a balance between the recovery rate and the purification effect;

Elution:

Allows a solvent with a strong elution ability to pass through the adsorbent, interrupting the interaction between the adsorbent and the retained compound, allowing these compounds to flow out of the adsorbent with the solvent; usually, it is just right The elution solvent for eluting the target compound is selected, and at this time, less interferent is washed off, and a balance point between the recovery rate and the purification effect is also required when selecting the eluent;

Breakthrough:

When the retention capacity of the adsorbent is weak or the mass of the compound exceeds the capacity of the adsorbent, some or all of the target compounds are not retained and flow out of the cartridge during the loading process; this phenomenon is an operational accident and should be avoided. occur.

Conditioning:

The initial step in preparing the SPE sorbent by running a solvent through it to activate and equilibrate the sorbent.

Sample Loading:

The step in which the sample is introduced onto the SPE sorbent, allowing the target analytes to interact and be retained.

Recovery:

The percentage of the target analytes that are successfully eluted from the SPE sorbent and collected for analysis.

Retention Time:

The time it takes for a compound to move through the SPE sorbent during sample loading, often influenced by the affinity between the compound and the sorbent.

Selective Retention:

The ability of the sorbent to preferentially retain certain analytes over others based on chemical interactions.

Interference:

Unwanted substances in the sample that may affect the accuracy of the analysis or the performance of the SPE.

Guard Column:

A short column placed in front of the analytical column to protect it from contamination or damage, especially in reversed-phase chromatography.

Reversed-Phase:

A type of SPE sorbent where the stationary phase is less polar than the mobile phase, often used for the retention of nonpolar and moderately polar compounds.

Ion Exchange:

A type of SPE sorbent that uses charged functional groups to selectively retain ions based on their charge.

Normal-Phase:

A type of SPE sorbent where the stationary phase is more polar than the mobile phase, suitable for the retention of polar compounds.

SPE Disk:

A solid phase extraction device that consists of a disk-shaped sorbent material, commonly used in disk-based extraction techniques.