Hadi Taban - Department of Environmental Geology, Research Institute of Applied Sciences (ACECR), Shahid Beheshti University, Tehran, Iran.
Ali Reza Fakhari - Department of Pure Chemistry, Faculty of Chemistry, Shahid Beheshti University, G. C., P.O. Box ۱۹۳۹۶-۴۷۱۶, Evin, Tehran, Iran

Introducing new sorbents is an interesting and debatable issuein the field sample preparation. In this study, for the first time, a pH-sensitive magnetic microgel, Fe3O4–SiO2–poly(4-vinylpyridine), was introduced as a smart sorbent The operating mechanism of this sorbent is based on changing the pH value of the sample and consequentto thatthe structure of this pH-sensitive microgelis changed. So that, in pH = 6 the microgel was ready to accept and load the analytes (partial swelling), and when the pH was raisedto 8.0, the microgel was closed and analytes were trapped insidethe sorbent (deswelling). In pH = 2 the microgel was opened and the analytes were released from the microgel (swelling). As the adsorption and desorption mechanism was based on changing the pH and only aqueous medium was used as effluent solvent, this method was introduced as a green extraction method. The use of this microgel resulted in excellent figures of merit. The limits of quantitation and detection for herbicides were obtained within the range of 10-30 and 3-10 ng mL-1, respectively. Finally, theproposedmethod was successfully applied to determine the oncentration of phenoxy acid herbicides as hazardous materials in environmental samples.

Capillary electrophoresis,Environmental samples,Phenoxy acid herbicides,pH-sensitive microgel, Smart sorbent