As in-line filters, pre-columns and guard columns have many similarities and differences simultaneously.
How to Differentiate Pre-columns From Guard Columns?
Being connected before column, both pre-columns and guard columns can prevent solid impurities from blocking the frit. The only thing inside pre-column is a frit that filters impurities whose particles are larger than aperture of frit. One can clean pre-column by ultrasound with water and methanol for 10 min.
Cartridges are inside guard column holders and they remain replaceable. Packing materials inside cartridges can not only filter solid impurities, but also absorb weak polarity and non-polarity organic impurities, which avoids contamination of packing materials.
How to Select the Guard Column?
How to choose a guard column without influencing separation and analysis? First and foremost, internal diameters should match as closely as possible while packing materials should be of the same particle size as the analytical column. For most analysts, the principle of selection is to find a short guard column and packing materials with weak retention for samples on the premise of meeting the requirement of separation and analysis. Because the longer the guard column is, the more packing materials it contains, the longer retention time it takes for samples.
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