Residues of plant protection product co-formulants in food - Substance selection and method development

In order to be able to determine their residues in and/or on foods of plant origin, analytical methods were developed for selected co-formulants of plant protection products. The solvents N,N-dimethyldecanamide (DMDA), cyclohexanone and components of solvent naphtha (including 2-methylnaphthalene), as well as the surfactant dioctyl sulfosuccinate (docusate), can now be quantified specifically and sensitively with LC-MS/MS or GC-MS on apples and a variety of vegetables.

Currently, only active substances, their metabolites and/or breakdown or reaction products are regulated as ‘pesticide residues’ in and/or on foods of plant origin while potential residues of co-formulants are ignored. In order to identify potential risks from residues of co-formulants on food, analytical methods to quantify such residues were developed for a set of co-formulants, selected based on previous work (Report: Co-formulants in plant protection products: Initial study on the risk assessment of co-formulants in plant protection products). Furthermore, in laboratory studies apples, peppers and tomatoes were treated with selected plant protection products and stored for up to 3 days before the co-formulant residues were determined. Residues of all four co-formulants, i.e. N,N-dimethyldecanamide (DMDA), cyclohexanone, components of solvent naphtha (including 2-methylnaphthalene) and dioctyl sulfosuccinate (docusate) were detected at levels greater than 0.01 mg/kg. Additionally, the co-formulant dioctyl sulfosuccinate was found on several types of vegetable purchased in retail trade (from a major Swiss distributor) at concentrations in the range from 0.002 to 0.1 mg/kg. The findings of this study form the basis for future field trials, which will allow gaining a sense of the actual quantity and the behavior of co-formulant residues under real agricultural conditions.