Method development guidelines: SPE using ISOLUTE® SAX and ISOLUTE® PE-AX SPE sorbents for the extraction of aqueous samples

ISOLUTE® SAX and PE-AX, the strong anion exchangers, are quaternary amines and therefore have a permanent positive charge under all pH conditions. Since this amine is tethered to the silica surface through a propyl linkage, these phases have limited non-polar character, and so secondary non-polar interactions with analytes are weak. This means that it may not be necessary to add an organic fraction to the elution solvent, which is often necessary when eluting from more hydrophobic sorbents in order to overcome non-polar retention mechanisms.
These two phases differ only in that ISOLUTE® SAX has a chloride counter ion while ISOLUTE® PE-AX has an acetate counter-ion.

Literature number: TN103.V.1