Normal Phase SPE Cartridge

A normal phase SPE cartridge is one in which the stationary phase is more polar than the mobile phase. It mainly utilizes the polar interaction between the polar surface of the solid phase extraction material and the polar functional group of the target.

Polar forces are stronger than nonpolar forces but less powerful than ionic forces. Common polar functional groups include hydroxyl, amine, mercapto, etc. A weakly polar matrix environment favors the formation of polar forces because weakly polar solvents do not have functional groups capable of forming hydrogen bonds with polar stationary phases.

Therefore, in the normal phase extraction of SPE, the sample matrix is mostly weak polarity, such as n-hexane, dichloromethane, rapeseed oil, etc., and most of the target objects contain polar functional groups.

Common polar stationary phases include silica gel, alumina, florisil, and bonded silica containing cyano (CN), and diol (2OH) groups.

In normal phase mode, the polarity of the solvent system should gradually increase in the order of sample solvent, eluting solvent, and elution solvent, and their elution strengths should also gradually increase. It must be ensured that the selected sample solvent cannot elute the target substance, and the selected eluent should elute the interfering substances to the maximum extent without eluting the target substance, so the eluent should be able to completely elute the target substance.