Choosing Solid Phase ExtractionColumns: A Concise Guide

These factors often pose challenges in sample pre-processing experiments, making the selection of solid phase extraction columns a daunting task.

So, how to choose the appropriate solid phase extraction column?

1. Selecting the Solid Phase Extraction Sorbent Based on Sample Matrix

Begin by assessing whether the sample matrix falls within the category of aqueous solution, polar organic solvents, or non-polar organic solvents.

When dealing with a sample matrix composed of non-polar organic solvents, it is common to opt for a polar column. If the desired outcome is not achieved, one can resort to evaporating the organic solvent and reconstituting it in water for subsequent treatment as an aqueous solution.

For sample matrices containing polar organic solvents, dilution with deionized water or evaporation followed by reconstitution in water allows for aqueous solution processing.

In the case of water-based sample matrices, it is imperative to ascertain whether the target analyte can undergo ionization. If the target analyte remains in a neutral state in the aqueous solution, a hydrophobic non-polar sorbent is chosen. If the target analyte undergoes ionization, consideration should be given to whether the primary interfering substances exist in an ionic or neutral state. When interfering substances are ionized, a hydrophobic non-polar sorbent is selected, while for those in a neutral state, an ion exchange column is chosen.

Reference Guide for Commonly Used Solid Phase Extraction Sorbent Selection

2. Selecting the Column Specification Based on Sample Load

The capacity of a solid-phase extraction (SPE) column refers to the adsorption capacity of the column packing material.

For silica gel-based SPE columns, their capacity typically ranges from 1 to 5 mg/100 mg, with a column capacity of 1% to 5% of the packing material mass. For instance, a 100 mg/mL C18 column can retain up to 5 mg of compounds.

Polymeric-based SPE columns have a capacity three times that of silica gel-based columns, generally around 15% of the packing material. For example, a 100 mg/mL HLB column can retain up to 15 mg of compounds.

The capacity of ion exchange adsorbent packing is expressed in meq/g, representing the capacity of the packing material in milliequivalents per gram. The capacity of such materials typically ranges from 0.5 to 1.5 meq/g.

When selecting the specifications of an SPE column, it is essential to consider not only the target compounds but also potential interferents that may be adsorbed under extraction conditions. Therefore, the selection should be based on the total amount of both, and it is generally recommended that the column capacity be at least twice the content of the target compounds to avoid overload issues.