Qiaex II Gel Extraction Kit

Patrick F.H. Lai the Graduate Student pfhlai at LOOKSMART.COM
Tue Sep 1 08:19:23 EST 1998

---- Begin Original Message ----
Dear all,
I am using Qiaex II Gel Extraction Kit to extract a very well amplified 500bp 
PCR product from agarose gels. Using special agarose (SEAKEM GTG), did not 
overdry the pellet, and was using TE buffer pH 8.0 (pH of MiliQ is too low) to 
redissolve the DNA...  changed all variables in the system...
However, final DNA yield was always very low  (aprox 7ng/ul), miles away from 
the 60%  efficiency given by Qiagen.
Does somebody have a solution to this problem? 

I appreciate your help!

---- End Original Message ----

Hi !  Dr. Beat,

My experience with the QIAEX II kit is that yield is always going to
be variable.
Some of the tricks that I have tried and seemed helpful include:
1.  Elute twice in T or TE at pH 8.5, with the second elution done
with SDDW at 50 deg C, then lyophilize and resuspend at the volume of
the T or TE in the first elution.
2.  Try the PCR purification Kit from QIAGEN, it often works more
 reliably, .... I don't know why, though.  Longer shelf live ?
3.  Re-amplify by PCR with whatever 7ng/uL DNA recovered as template,
and hope to get more DNA the second time purifying DNA with the kit.

I once talked to a QIAGEN rep about this same problem of yours.
He said TE often drops its pH if it has been left on the shelf too
long, and  this lowers the recovery.  
That's why new kits now come with T at pH 8.5.

Hope this is useful info.   :-)

Patrick F.H. Lai  < PFHLai at looksmart.com >
Graduate Student
University of Toronto
Toronto, Ontario, Canada

LookSmart … or keep looking.

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