Development of a selective sorbent for the solid-phase extraction of terbuthylazine in olive oil samples: a molecular imprinting strategy.

Aiming to implement an analytical methodology that is highly selective for the extraction and quantification of terbuthylazine from olive oil, we successfully achieved: (i) the development of a molecularly imprinted polymer by bulk polymerization using terbuthylazine as template molecule, methacrylic acid as functional monomer, ethylene glycol dimethacrylate as cross-linker, and dichloromethane as porogen; (ii) characterization of the imprinting material using Fourier transform infrared spectroscopy, thermogravimetric analysis, nitrogen adsorption at 77 K, and scanning electron microscopy; (iii) their molecular recognition for the template molecule using high-performance liquid chromatography, and (iv) optimization of a solid-phase extraction procedure using as sorbent the synthesized molecularly imprinted polymer for the selective extraction and clean-up of terbuthylazine from spiked organic olive oil and further quantification of the pesticide levels by high-performance liquid chromatography. The suitability of the implemented analytical methodology was demonstrated, as concentrations of terbuthylazine below the tolerated maximum residue limits in the spiked organic olive oil samples could be satisfactorily analyzed with good precision/accuracy with high recovery rates (96%). Overall, the implemented methodology has proven to be reliable and robust and is highly promising in the field of sample preparation, particularly for the isolation/preconcentration of terbuthylazine in complex food samples.

Volatile organic compound adsorption on a nonporous silica surface: how do different probe molecules sense the same surface?

In this work, we compare experimental results to molecular simulation results of volatile organic compound (VOC) adsorption on nonporous silica. We adopted an effective model for the rough solid surface, obtained by a temperature annealing scheme, plus an experimental/simulation nitrogen adsorption tuning process over the silica energetic oxygen parameter. The measurement/prediction of selected VOCs, specifically, n-pentane and methylcyclohexane, is presented in terms of adsorption isotherms, with an emphasis on the angle distribution analysis of the three studied probe molecules with respect to the same modeled surface.