For cleanup,a multi-layer Supelclean Envi Carb-II/PSA SPE cartridge was conditioned
with 5 ml of acetonitrile:toluene (3:1, v/v). Acetonitrile extract was loaded and the retained pesticide was eluted weakly, in a 40 mL glass vial, with a volume of 20 ml of acetonitrile:toluene
(3:1, v/v). The eluate was evaporated till dryness under a stream of nitrogen and filled up to a final volume of 2 mL with acetone containing the three analyte protectants (3-ethoxy-1,2-propanediol at 10 g/L; and D-sorbitol and L-gulonic acid c-lactone at 1 g/L; respectively).