Retention and Determination of Polycyclic Aromatic Hydrocarbons from Urban Air Based on Recycled Polyurethane Foam Modified with Expanded Polystyrene

Expanded polystyrene (EPS) and polyurethane foams (PUFs) are widely produced and used due to their properties and, recently, it has been described that polystyrene present π–π interactions. Therefore, this work proposes to use recycled EPS to modify the surface of PUFs for the retention of 12 polycyclic aromatic hydrocarbons (PAHs) in air samples. PUF cylinders were modified with recycled polystyrene and characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and affinity experiments. The proposed material is suitable for the retention-elution of PAHs from air samples, and can be incorporated to liquid chromatography generating a quantitative methodology. This methodology is efficient, fast and use lower volumes of organic solvents compared with other methodologies. Eighteen urban air samples were collected and analyzed weekly, using principal component analysis (PCA), and a relation between meteorological parameters and concentration of PAHs was observed.</p

Effects of Bentonite on p-Methoxybenzyl Acetate: A Theoretical Model for Oligomerization via an Electrophilic-Substitution Mechanism

Tonsil Actisil FF, a commercial bentonitic clay, promotes the formation of a series of electrophilic-aromatic-substitution products from para-methoxybenzyl acetate in carbon disulfide. The molecules obtained correspond to linear isomeric dimers, trimers, tetramers and a pentamer, according to their spectroscopic data. A clear indication of the title mechanistic pathway for the oligomerization growth was obtained from the analysis of a set of computational-chemistry calculations using the density-functional-theory level B3LYP/6-311++G(d,p). The corresponding conclusions were based on the computed dipole moments, the HOMO/LUMO distributions, and a natural-populations analysis of the studied molecules