Preparation of stir bars for sorptive extraction based on monolithic material

A stir bar for sorption extraction based on monolithic material (SBSEM) was prepared in this study. The monolithic material was obtained by in situ copolymerization of octyl methacrylate and ethylene dimethacrylate in the presence of a porogen solvent containing 1-propanol, 1,4-butanediol, and water with azobisisobutyronitrile as the initiator. The influences of polymerization parameters and the thickness of monolithic materials on the adsorption and desorption efficiencies were investigated, using naphthalene, phenanthrene and fluoranthene as detected solutes. The results show that monolithic material possessed good permeability resulting in fast adsorption and desorption for detected solutes. Spiked seawater samples containing eight polycyclic aromatic hydrocarbons (PAHs) and urine samples containing four anabolic steroids were preliminarily analyzed by using the sorptive bars and liquid desorption followed by high performance liquid chromatography with diode array detection. The results demonstrate that prepared stir bar was suitable for preconcentration of both apolar and polar analytes. The enrichment factors for phenanthrene, anthracene and pyrene were 150, 134 and 189, respectively. The SBSEM shows good batch-to-batch reproducibility and good stability, and can be reused a least 10 times for the extraction of polycyclic aromatic hydrocarbons in seawater.