Preparation and characterization of polydimethylsiloxane containing cyano/phenyl groups for potential use in sorptive extraction

A coating of poly(dimethylsiloxane) (PDMS) on a stir bar is typically used for sorptive extraction and preconcentration of nonpolar organic analytes from aqueous matrices. Here, we used sol–gel to synthesize three new coatings based on hydroxy-terminated PDMS crosslinked with 3-cyanopropyltriethoxysilane (CN) and phenyltriethoxysilane (PH) with three molar ratios of CN:PH (2:1, 1:1, and 1:2). The water contact angle of the coatings was below 90°. Cyanopropyl and phenyl groups were identified by infrared spectroscopy. The coatings were thermally stable up to 200°C. Also, they were stable to organic solvents and aqueous solutions at different pH. Glass stir bars were covered with the coatings to explore its potential application in stir-bar sorptive extraction. The test included polar antibiotics (sulfathiazole, sulfamethoxazole, trimethoprim, and chloramphenicol) dissolved in spiked water (pH 4.5) and organic solvent. Different experimental conditions were used to explore the capacity of the coatings to extract and preconcentrate the antibiotics. Unsatisfactory results of enrichment effect were obtained in aqueous solutions of antibiotics. In organic medium, the antibiotics were extracted and preconcentrated with the three coatings.