The objective of this work was to assess the effect of adjuvants in the sorption in soils of the fungicides, cyprodinil and fludioxonil, usually applied together in a mixture commonly called 'Switch'. Water suspensions of a commercial formulation of Switch were used in phase partition experiments for a set of selected soils from vineyards. A clean-up procedure of the supernatant was developed for the phase separation in presence of the adjuvants prior to quantification of cyprodinil and fludioxonil. The maximum sorption on the solid phase (which includes soil and other solids from the commercial formulation of Switch) was 2000 mg kg(-1) for fludioxonil and 3000 mg kg(-1) for cyprodinil after incubation with 800 mg L(-1) of Switch. However, adsorption to soil particles were lower; fludioxonil concentrations adsorbed in soils range from 50 to 80 mg kg(-1) of soil and cyprodinil concentrations range from 120 to 260 mg kg(-1) of soil. Adjuvants increased the solubility of fludioxonil in pure water at 25 degrees C up to 5 times that of the pure substance (from 1.8 to 9 mg L(-1) in control samples), and show a strong influence on the adsorption in soil. Soil pH, effective cation exchange capacity and copper content due to past anti fungal copper-based sprays, have also influence on the adsorption of the active ingredients in presence of adjuvants. (C) 2011 Elsevier B.V. All rights reserved.