Help needed-- understanding POROS / Perfusion chromatography

Amos Heckendorf nestgrp at
Sun Mar 12 17:31:08 EST 1995

In article <01HNZ1025JVQ9I67YO at>, RMARTINQFD at BIOTECHNET.COM wrote:

> 1.  For what applications is the POROS  
> chromatography material especially suited for? 

I think they have a very good hardware package (no relationship) but I
continually argue against their separation materials, not because I don't
think they are good, but because I think we should be able to discuss
other alternatives that achieve the same goals.  They have a wide range of
chemistries for most applications.

The application Poros materials are overall are useful for is--fast
assays.  The defining arguements for Poros vis a vis NPR resins (nonporous
resins from several sources, which also give flattened Van Deempter
curves, and 1-3 min separations), resolve themselves down to the flow rate
(solvent consumption on perfusion is higher) and the pressures (once again
higher at optimum flow rate).  They would counter that the NPR resins
don't have the capacity, but that is not necessarily the case, since
comparable capacities by frontal analysis have shown that some NPR
materials compare equally with laod to some Poros materials.  What NPR has
that Poros doesn't is very sharp peaks (resulting in lower levels of
detection, smaller recovery volumes, etc).  Any time you have pores you
will have a diffusion contribution to the peak width. We recommend NPR
resins when the molecules are large and have a low difusion constant which
causes broadening.

We distribute medias and educate scientists on their other choices of
media. If you want to call or email me I can give you the various choices
available to you.  We think there are other options to choose from, though
one may not want to choose them.

> 3.For what applications is POROS not the 
> best choice?  What are it's disadvantages?
Process chromatography requires in many cases too much documentation of
batch history to justify the use of small columns which through multiple
runs can process a batch(es) of material.  When compared to using a larger
column (nonperfusive) but porous, which in a single run ccould process the
whole lot and thus would not push the documentation costs off into a
different department, we feel that the total operating costs would be
lower in a nonperfusive environment, unless the material being purified is
so labile or if there are no other longer processing steps in the process
to justify not shortening this purification step. The ratio of the
particle size (cost) to column length is fairly constant, so a large
particle long column will cost pretty much the same as a short column of
smaller particle size.  If you then argue that why not use perfusion in a
process, you then have to look at the capital costs of higher pressure
operation vis a vis lower pressure and those costs are substantial.

Call me if you want to discuss this further.

Amos Heckendorf (nestgrp at 800-347-6378 ; 508-481-6223
The Nest Group , Value Added Resellers for:
PolyLC, mfg of HPLC packings for Biomolecule Separations
The Separations Group, mfg of Vydac
Hydrocell NPR gels for ion exchange and HIC

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