The recently published guidance from EFSA on risk assessments for active substances that contain stereoisomers provides recommended approaches to address and assess data requirements for active substances with the same molecular formula but different three-dimensional orientations. The approach of synthesizing and testing each isomer individually is both costly and time consuming.
To optimize stereoisomer evaluation, advances in chromatographic separation techniques and instrumentation were applied by Rory Mumford, Senior Manager of Accurate Mass Spectrometry from the Smithers laboratory in Harrogate, UK. 2D-HPLC uses reverse phase columns attached in series to reverse phase chiral columns. Using sophisticated sample switching, peaks containing multiple stereoisomers from the first reverse phase column can be routed to the second chiral column for deconvolution – enabling subsequent identification by tandem mass spectrometry.
This approach provides robust investigation of chiral profiles of agrochemicals and their metabolites without the need for separate isomer studies or extensive sample isolation, workup, and subsequent chiral chromatography. The solution provides a routine, accurate quantitation of stereoisomer levels in environmental fate, metabolism, ecotoxicology and residue studies.
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