Evaluation of a solid-phase extraction dual-layer carbon/primary secondary amine for clean-up of fatty acid matrix components from food extracts in multiresidue pesticide analysis.

The use of dual-layer solid-phase extraction (SPE), a primary-secondary amine (PSA) in combination with graphitized carbon black (GCB), was evaluated for sample clean-up during multiresidue pesticide screening of agricultural and food products. The retention of fatty acids by the PSA sorbent was quantified and the effect of the elution solvent on the retention of fatty acid on the SPE cartridge was evaluated. The use of stronger elution solvents to elute certain pesticides from graphitized carbon was shown to interfere with the capacity of PSA to bind fatty acids. A suitable protocol was tested using GCB/PSA dual-layer SPE to clean-up several food matrices and to simultaneously screen multiple fortified pesticides with a wide range of physico-chemical properties. With a few exceptions, pesticide recoveries were between 85% and 110%, and sample-to-sample differences of less than 5% were achieved, demonstrating the versatile suitability of the dual-layer SPE to sample clean-up.