I'm trying to find sample preparation cartridges based on size exclusion. I'm extracting additives from polymers. In case of some materials the polymer is co-extracting and interfering LC detection. I would like to get rid of the polymer by size exclusion before LC analysis but haven't yet find this kind of product. Please let me know if you know a manufacturer. I would also be grateful to here if somebody has similar experiences.

What are the molecular weights of the additives and the polymer? What is the polymer? Or what is the stuff soluble in?

Might it be possible to do your work in one step with restricted access columns?

Theoretically, you can try ANY polar-bonded silica-based SPE device provided your loading solvent is sufficienty polar such that there is no normal-phase retention of your compound (water would be the best). Solubility will need to be confirmed. If you believe that a 300A pore size material is appropriate, Waters offers a 300A diol-bonded Sep-Pak(R) device. The material is the same that is used in may SEC applications for protein samples. For 125A pore size material, I would recommend the amino-propyl (NH2) bonded Waters Sep-Pak(R) device. The true issue will be one of separation efficiency, as size-exclusion will be inherently LOW efficency (and with low plate SPE devices, you may not observe any usable separation between the large and small compounds). You may be better off with a reversed-phase or normal-phase SPE clean up approach, wherein you adsorb the smaller compound of interest and the larger compounds may be excluded from the pores of the SPE device material (I would recommend the smaller 125A pore size materials for this), and you can then elute your smaller compounds in a cleaner fraction. The choice of normal- vs. reversed-phase approaches may come down to solubility (if your sample is water-soluble, reversed-phase would be a good choice; if your sample is only soluble in non-polar solvents like hexane, etc, then normal-phase would be the way to go). Good luck.

Dear Anonymus;

It sounds like you can use some adsorbent that combines GPC and RP modes. Give a call to Diazem Corp.(989-832-3612). They manufacture many different types of restricted access materials for sample cleanup problems, such as metabolites in plasma or similar. It is possible they have a material you can use of the right porosity and surface treatment.

Good luck;

Benjamin

In size exclusion, the separation takes place within one column volume. The SPE cartridges have low efficiency and the separation is usually based on step gradient elution, although some SPE for desalting of proteins (usually longer bed length - 5 -10 cm) based on SEC exists. I doubt SPE based on SEC for your application can be found. Besides, the interfering substances can be monomers or oligomers not different sufficiently in size.

In case the previously recommended approaches are not suitable, preparative SEC/GPC cleanup commonly used for isolation of PAH/PCB/pesticides from oils/fats may help. Please contact me for more details.