extraction solvents for pesticides

[Karl DeWahl <dewah001@tc.umn.edu>]

We have an intern looking for alternatives to methylene chloride used to 
extract a variety of pesticides from water (surface waters, run-off etc.). 
 The application is lab analysis occurring at the state Ag. Dept.  The 
extractant needs to be nearly insoluble in water,  needs affinity for a 
wide range of common pesticides, and it needs to be safe.  The scale of use 
is small - 300ml/sample,  300gal/year.

Does anyone know of an alternative being used in a similar application?

Any thoughts on a possible alternative?

These are two leads we are pursuing, any additional information on these 
would also be appreciated.
1. diethyl carbonate - water insoluble, has Hansen solubility parameters as 
close to MeCl as we were able to find for non-halogenated solvents. 
 Described as mildly toxic.  Does not appear to have an OSHA PEL.

2. Ionic liquids - these are organic salts that are liquid at near ambient 
conditions.  Research on them is being carried out at the University of 
Alabama (http://bama.ua.edu/~rdrogers/webdocs/RTIL/).  They are claimed as 
environmentally friendly, but they are expensive.  Its not clear if any 
developed would work for this application, or if they have moved out of the 
research phase at all.  We are trying to contact the Alabama researchers.