Aligned porous structures of polystyrene prepared by directional freezing–phase separation for micro-solid phase extraction

In this work, a directional freezing-phase separation method for the preparation of aligned porous materials using polymers as an extracting medium is introduced. Phase separation method using anti-solvent of selected polymer in liquid nitrogen was used to fabricate the align structures [1]. These structures mostly contain well-aligned microchannels and exhibit good mechanical properties and high porosity. Many publications have been investigated the fabrication of align structures using different polymers such as polyurethane, polyvinyl alcohol and polystyrene [3]. For synthesizing the aligned porous materials, a polystyrene solution in dimethylformamid (5-15% wt%) was frozen using liquid nitrogen then in phase separation stage, methanol was used as anti-solvent [1,2]. Eventually, the aligned porous polystyrene was dried in air and used as a sorbent for extraction of polycyclic aromatic hydrocarbons from the aquatic media. After direct extraction, the extracted analytes were desorbed into acetonitrile by the ultrasonic radiation. The desorbing solvent was dried under the nitrogen flow and then sufficient amount of acetonitrile containing 100 mg L-1 linden as the internal standard was added. Finally, an aliquot of 2 µL of the solution was subsequently injected into GC-FID. The extraction efficiency of aligned porous polystyrene was compared with the granule polystyrene and the synthesized polystyrene by phase separation without exposing to the liquid nitrogen.