Waters offers PoraPak™ Rxn, a family of polymer-based chromatography products for superior cleanup of synthetic reactions. PoraPak Rxn products are available in two chemistries: PoraPak Rxn CX, a strong cation-exchange sorbent and PoraPak Rxn RP, a reversed-phase sorbent.
PoraPak Rxn sorbents are based on copolymers that exhibit the following properties:
Choose the best product and technique for your cleanup
PoraPak Rxn products are available in two sorbents: CX, a strong Cation-eXchange resin and RP, a Reversed-Phase resin. The illustrations below recommend the sorbent to use and the separation technique to apply during cleanup. The choice of the appropriate sorbent and technique depends upon the nature of the reaction products, reactants, solvents, and/ or preparative columns.
Catch and Elute
In the "catch and elute" technique, the reaction mixture is loaded onto the cartridge; the analytes of interest are retained by the sorbent. A wash step follows to remove additional reaction components from the cartridge. A strong solvent is used to elute the analytes from the cartridge. Sample concentration results when the final elution volume is smaller than the load volume.
In the pass-through technique, the sorbent does not retain the compounds of interest, but does retain some class(es) of compounds and impurities, that can be discarded with the column. Fractionation is achieved by the interaction between the impurities in the reaction mixture and the sorbent. No sample enrichment occurs during the solid-phase extraction (SPE) step.
In the adsorption chromatography technique on a reversed-phase sorbent, the neutral compounds are moving down the chromatographic column in the presence of organic solvent, albeit slowly, for small-percent organic washes. Load the reaction mixture in high water content (75% water for example), wash to remove polar compounds, and then increase the organic content in large increments to elute neutrals. The increase is determined by the hydrophobicity and MW of the compounds.
Using PoraPak Rxn CX: Strong Cation-Ion Exchange Catch-and-Elute and Pass-Through Protocols
Using PoraPak Rxn RP: Reversed-Phase Protocol
For a compound to be retained, a reaction, carried out in a polar organic solvent will have to be concentrated by evaporation and/or diluted with water (3-to-1 or greater). This dilution brings the organic content down to 25% or less so as to enable reversedphase retention. The generic protocol, shown to the right, can be used as a starting point to clean up reaction mixture.