Synthesis and application of molecularly imprinted silica for the selective extraction of some polar organophosphorus pesticides from almond oil

The aim of this work was to prepare and evaluate molecularly imprinted polymers obtained by a sol-gel approach for the selective solid-phase extraction (SPE) of organophosphorus pesticides (OPs) from almond oil. The performances of molecularly imprinted silicas (MISs), prepared using different conditions of synthesis, were studied by applying different extraction procedures in order to determine the ability of the MISs to selectively extract ten target OPs. For this, the retention of OPs on MISs in pure media was compared with the retention on a non-imprinted silicas (NISs), used as control sorbent, to prove the presence of specific cavities. The most promising MIS allowed the selective extraction of the 3 most polar OPs among the 10 studied. The capacity was studied and the repeatability of the extraction recovery yield was demonstrated both in pure and real media. This MIS was able to selectively extract fenthion sulfoxide and dimethoate contained in almond oil extract after applying the optimized extraction procedure with recovery yields between 100 and 114%. The estimated limit of quantification (LOQ, S/N = 10), thanks to LC/MS analysis in MRM mode, between 1.2 and 4.6 μg/kg for those OPs in the almond fruits, was more than 10 times lower than the Maximum Residue Levels (MRLs) established by the European Commission. This MIS therefore shows a high potential for the analysis of those two polar OPs at trace levels from almond oils.