This Test Guideline describes how to plan and carry out processing studies, i.e. determine residue levels in primary processed commodities following pesticide application on raw agriculture commodities (RAC) under conditions likely to lead to maximum residues. It provides the distribution of residues (active ingredient, and/or metabolites, degradation products), and preferential accumulation in various processed products resulting from the processing of a commodity.

Used RACs (of plant origin and animal origin) should contain field-treated quantifiable residues, at sufficient levels so that concentration/dilution factors for the various consumed products and non-consumed intermediates can be determined. Pesticides residues to be measured are determined by the residue definition based on studies on the nature of the residue in processing and/or in plant and livestock. For each field test site (at least two independent) the processing factor (Pf) is calculated as the ratio between the residue level in the processed commodity and in the RAC or the commodity to be processed. If a given commodity has two or more significantly different commercial procedures, two trials for each procedure are necessary. Spiked samples should be run concurrently with those from the processing study to ensure the method validity.