There are many really great sample prep techniques out there for biological samples.  Many are “affinity-based,” meaning that they take advantage of some kind of binding effect between the bioparticles and some kind of “handle.”  These kinds of processes can not only concentrate biological samples, they can help purify them and get rid of interferents that spoil the identification method.  Of course, this is pretty difficult and expensive if the sample is very large (more than about a milliliter) because a lot of expensive reagents would be needed.  At least a dozen great examples of this sort of method were presented at this conference. 

 
Other sample prep techniques include charge-based or sonic focusing to clean up and concentrate samples.  Again, this is usually pretty hard to do with a sample more than about a milliliter, due to the physical scale of these effects.  Several examples of these techniques, and others, were presented at SamplePrep 2010. It was an excellent conference, by the way; Serge Pann at the Knowledge Foundation put it together.
 
The InnovaPrep physical concentration is a great way to bring the sample volume down to a milliliter or less, so these other techniques can be applied efficiently.  An example of where this works well is analysis of environmental waters for DNA, which is physically a lot like the humic acids that come from rotting vegetation (Slide 12).   First, concentrate the sample down from the initial size to a milliliter or less, then apply your secondary sample prep if needed.  
 
For my example, where the sample contains target DNA and non-target humic acids, we first concentrate samples using the InnovaPrep and then apply  the charge-based SCODA system that Dr. Marziali developed at Boreal Genomics.  Next, I’m going to talk a little bit about where Biodetection is headed in the future.

+Dave