The distribution of 19 azole class pesticides in hexane/aqueous–organic mixtures systems and rapeseed
oil (or oil solution in hexane)/organic solvents has been studied at 20 ± 1 C. The distribution constants
(P) and coefficients (D) between hydrocarbon and polar phase are calculated. It is found that all the studied
pesticides are hydrophobic, i.e., in hexane–water system logP0. Replacement of water by organic
solvents results in sharp logP falling, and their values become negative. It is revealed that solutions of
strong inorganic acids in anhydrous acetonitrile extract azole class pesticides from hexane and vegetable
oils most fully and selectively. In particular, the acidification of acetonitrile causes a drop of D values in
50–2000 times for the majority of the studied pesticides. This phenomenon was used for the development
of the improved technique for the quantitative analysis of a widely used azole class pesticides,
which can be presented at trace levels in rapeseed oil. The proposed methodology is based on dissociation
extraction (DE) of azoles using perchloric acid in anhydrous acetonitrile, with following clean-up of acetonitrile
extract from organic impurities by hexane and aqueous solution of dipotassium hydrogen orthophosphate,
and final GC–ECD (gas chromatography with electron capture detection) determination of
azole fungicides. The values of obtained recoveries were between 85% and 115% with RSD values below
10%. The obtained limits of quantitation, ranged from 3.0 to 300 lg kg1, are below the maximum residue
levels (MRLs) set by the European Union for the majority of pesticides. The developed method was successfully
applied to different rapeseed oil samples