Relation factor: a new strategy for quality control in the determination of pesticides in environmental aqueous matrices.

The effects promoted by environmental aqueous matrices on pesticide determinations have been assessed, and for the first time, a simple, low-cost and efficient strategy for the correction of analytical results has been determined. This method can be useful as a parameter of quality control in a quality assurance programs. Evaluation of the matrix effect showed that environmental aqueous matrices, e.g., estuarine water, promote a distinctive and significant effect on the determination of pesticides. The picloram, atrazine and methyl parathion pesticides suffered the smallest effects promoted by the estuarine matrix, whereas chlorpyrifos and cypermethrin suffer a significant effect. For picloram, the matrix effect was a function of its physiochemical properties. However, for atrazine, methyl parathion, chlorpyrifos and cypermethrin, the matrix effect was promoted by environmental matrix components. As strategy for analytical quality control, it has been determined that there are relation factors (RFs) between pesticides and the selected surrogates standards. These RFs are not altered by the complexities and compositions of simple and complex aqueous matrices. Predetermined RFs was applied to the picloram, atrazine and methyl parathion assessment in a real sample from the estuary of the Jaguaribe River, and the results showed that when no quality control was applied, the concentration levels would be underestimated, leading to incorrect results and inaccurate conclusions.