HPLC problems

Peter pxpst2 at vms.spam.suxs.cis.pitt.edu
Fri Apr 3 09:03:29 EST 1998

In article <199804030350.TAA00239 at norway.it.earthlink.net>,
stsiembieda at EARTHLINK.NET ("Siembieda family") wrote:

> Does anyone separate low molecular weight DNA by HPLC.  I am currently
> working with a  DEAE TSK NPR column and having trouble with back pressure
> increases. 

If you are noticing the pressure increasing and decreasing by more than
~50 psi then you probably have air in the column.  I am assuming that you
are using a two piston pump.  For single piston pumps you may see pressure
increases >50 psi.  
Another possibility is that your outlet/inlet checkvalves may not be
seated corectly or they are dirty.  Consult your manual for cleaning

Since your most probable problem is air in the column, I would suggest you
reveiw your procedure for solvent degassing and sample preperation.  It is
sometimes possible to reverse the column and purge the air out but this
will decrease the life of the column.  Also air in the column will
decrease the capacity of the column due to channelling.  With your column,
you sould have gotten instructions as to its care and maintinance.  It
should give you detailed instructions on its "revitalization".


"Don't you eat that yellow snow
            watch out where the Huskies go"    FZ


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