Development of a stirring–assisted ferrofluid–based liquid phase microextraction method coupled with dispersive liquid–liquid microextraction for the extraction of some widely used pesticides from herbal distillates

In present study, a new sample pretreatment method based on the combination of stirring-assisted ferrofluid-based liquid phase microextraction and dispersive liquid–liquid microextraction has been developed for the extraction of some pesticides (diazinon, deltamethrin, fenpropathrin, phosalone, prometryn, simazine, and terbutryn) from herbal distillate samples. In this method, a few microlitre of a synthesised ferrofluid as an extraction solvent is added into the sample solution containing the analytes and the mixture is stirred at a high rate to increase the contact area between the ferrofluid and sample solution. Then the stirring procedure is stopped and the ferrofluid droplets containing the analytes are collected on the surface of stir bar. In the next step, the stir bar is washed with acetonitrile. In the following, the obtained mixture of acetonitrile and ferrofluid is rapidly injected into deionised water. The ferrofluid droplets are settled down at the bottom of a conical test tube and after back-extraction of the analytes into n-hexane, an aliquot of the extractant phase is injected into gas chromatography–mass spectrometry. Under optimum conditions, the introduced method offered high enrichment factors (1643−1884) and extraction recoveries (82–94%), low limits of detection (3.1–7.3 ng L–1) and quantification (10.3–24.3 ng L–1), and an acceptable repeatability (relative standard deviation ≤ 7.9%).