RESUMEN
An in-situ formed polymer-based dispersive solid phase extraction in combination with solidification of floating organic droplet-based dispersive liquid-liquid microextraction was developed for the extraction of neonicotinoid pesticides from milk samples. The extracted analytes were determined using high-performance liquid chromatography-diode array detector. In this approach, after precipitating the proteins of milk using a zinc sulfate solution, the supernatant phase (containing sodium chloride) was transferred into another glass test tube, and a homogenous solution of polyvinylpyrrolidone and a suitable water-miscible organic solvent was rapidly injected into it. By this step, the polymer particles were re-produced and the analytes were extracted onto the sorbent surface. In the following step, the analytes were eluted with an appropriate organic solvent to use in the following solidification of floating organic droplet-based dispersive liquid-liquid microextraction step that was done to acquire the low limits of detection. Under the optimized conditions, satisfactory results consisting of low limits of detection (0.13-0.21 ng/ml) and quantification (0.43-0.70 ng/ml), high extraction recoveries (73%-85%), and enrichment factors (365-425), and good repeatability (relative standard deviations equal or less than 5.1% and 5.9% for intra- and inter-day precisions, respectively) were obtained.