Characterization of fat soluble residues in biological matrices can be extremely challenging, especially when present at trace levels. Occasionally, residues present in fat tissues or lipid containing plant matrices can closely resemble natural fatty acids or other lipids. This structural homology, combined with large amounts of soluble natural products, makes separation via chromatographic methods, detection at low levels, and identification difficult. Guidelines for conduct of crop or livestock metabolism studies state that residues at levels between 0.01-0.05 mg/kg and representing &gt;10% of the total relative amount present should have significant attempts made to identify, but characterization might be accepted.  A review of different instrumentation and strategies utilized to characterize fat soluble residues will be presented. Examples will be discussed where residues near trigger values for identification are characterized or identified using various chromatographic and chemical modification techniques. A comparison of a few case studies will demonstrate examples of successful characterization/identification of metabolites in fractions containing endogenous lipids. Other examples will be presented in which metabolites are characterized, but techniques utilized were not successful at separating metabolites from natural products and identification.

Characterization of fat soluble metabolites of agrochemicals in biological matrices

254th National Meeting (2017)

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