Simultaneous electron capture detection of chlorpyrifos and 3, 5, 6-trichloro-2-pyridinol residues in peach and bahia grass field samples following gel permeation cleanup.

: A recently published method involving the simultaneous extraction, gel permeation cleanup, and electron capture gas chromatographic detection of residues of the insecticide and acaricide chlorpyrifos and its principal metabolite 3,5,6-trichloro-2-pyridinol is successfully applied to Lorsban-treated peach and Bahia samples. Previous quantitation of these compounds has required 2 separate analytical procedures. Multilevel temperature programming and manipulation of the gel permeation column effluent rate are the only adjustments of experimental parameters necessary to avoid large amounts of gas chromatographic interferences. Chromatographic peaks are more clearly defined and easier to integrate with the multilevel program than they are with 2-step or linear programs. This is one reason that recovery data are improved over those reported for the method as applied in the pea vine work. Residue analysis conducted on field-treated peaches and Bahia grass show the newly published procedure to be sensitive and effective.