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Re: extraction solvents for pesticides



For certain pesticides, the alternative is a different analytical method
that does not involve the use of solvents.  For example, California
water quality agencies have had good success with the ELISA method for
analyzing low concentrations of organophosphate pesticides in surface
water (rain, runoff, etc.).  The method is relatively accurate (accuracy
comparable to the EPA-approved method), significantly less expensive
than the EPA method, and does not require extractions.

FYI, if the laboratory needs to use an EPA-approved analytical method,
it must use the EPA-approved extraction solvent.  

Kelly Moran
TDC Environmental

Karl DeWahl wrote:
> 
> 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.