The message posted by Michael as a follow-up to Wagner's question about
Sephasyl shows that there are not really bad stationary phases around. If
one chooses carefully and knows what he or she is looking for,
satisfaction is pretty likely.
The thing with Sephasyl is that it has very specific selectivity -- for
certain compounds quite different from what one is used from other C18 RP
sorbents. That doesn't mean that this stationary phase is better or
worse, it's just different. It could perform exceptionally well on a
peptide the investigator is focusing his or her research. And that's
something that has to be considered: if one commits to such a material he
or she probably will have to stick with it in order to be able to compare
separations of different proteins or peptides.
As far as life expectancy is concerned it is in general rather the usage
that kills a column and not poor construction of the column or unstable
sorbent. As we often have very diluted samples -- see Deb McMillan's
answer on "AAA perspective" and she is right -- loading of such a huge
sample especially on a smaller column often rocks the whole bed of the
column. One has to consider that the loop volume is not under pressure.
Hence, once the loop is switched into the system, this generates a sudden
decompression which eventually will damage the column and shorten its
life.
Of course there will always be evolution -- a recent one was RP sorbents
that still give good separation without the use of TFA, this to avoid
signal suppression in ESI-MS generated by TFA.
Wagner: to know if Sephasyl is for you or not, give Pharmacia a few
typical samples of yours, tell'em your conditions and have them separate
these samples -- if you like what you see, well then Sephasyl and you
would probably make a good match, if you don't like it, keep going with
what you are using or try something else.
I know that this answer is not very conclusive, but I hope it gives you
an understanding of the implications of choosing a material.
Best regards: Jean-Pierre
******************************************************
Jean-Pierre Salzmann
Project Manager
LC Packings (USA) Inc.
80 Carolina Street
San Francisco, CA 94103
Phone (415) 552-1855
Fax (415) 552-1859
E-mail: jpsalzmann@earthlink.net
www.lcpackings.com
*******************************************************