Selective extraction of Bactrocera oleae sexual pheromone from olive oil by dispersive magnetic microsolid phase extraction using a molecularly imprinted nanocomposite

Bactrocera oleae Gmelin, also known as olive fruit fly, is the main olive tree pest. It produces a severe effect not only on the productivity but also on the quality of the olive-related products. In fact, the oil obtained from infected olives has a lower antioxidant power. In addition, an increase of the oil acidity, peroxide index and UV-absorbance can also be observed. 1,7-dioxaspiro-[5,5]-undecane (DSU), is the main component of the sexual pheromone of this pest and may be used as marker of the pest incidence. In this context, the development of new methods able to detect the pheromones in several samples, including agri-food or environmental ones, is interesting. In this work, we synthesized a molecularly imprinted polymer (MIPS) layer over magnetic nanoparticles (Fe3O4@SiO2@MIP) for the selective recognition of DSU. They were prepared using DSU as template and 3-aminopropyltriethoxysilane (APTES) to associate the target analyte on the surface of the magnetic substrate and the later polymerization of ethylene glycol dimethacrylate (EGDMA) in presence of 2,2-azobisisobutyonnitrile (AIBN). The resulting Fe3O4@SiO2@MIP composite was characterized by different techniques. The maximum adsorption capacity of DSU on Fe3O4@SiO2@MIP in hexane was 32 mg/g (5.3 times than that obtained for the non-imprinted composite). In addition, Fe3O4@SiO2@MIP showed a short equilibrium time (45 min) and potential reusability. The combination of dispersive magnetic microsolid phase extraction and gas chromatography with mass spectrometric detection allows the determination of DSU in real samples at concentrations as low as 10 μg/L with precision better than 7.5% (expressed as relative standard deviation). The relative recoveries are in the range between 95 and 99%, which indicates the potential of the methodology. Finally, it has been applied to real olive oil samples being the presence of the pest detected is some of them.