Role of nanoparticles in analytical solid phase microextraction (SPME)

Environmental context Organic hydrophobic compounds are present in water in low concentrations, and they can be analysed by means of a preconcentration technique called solid phase microextraction. We investigate the role of sorbing nanoparticles in the solid phase microextraction analysis of organic compounds. Our results show that nanoparticles are capable of partitioning between water and the solid phase and aggregate at the interface leading, most probably, to substantial overestimation of the original sample concentration. Abstract Solid phase microextraction (SPME) is commonly used to measure the free concentration of fairly hydrophobic substances in aqueous media on the basis of their partitioning between sample solution and a solid phase. Here we study the role of nanoparticles that may sorb the analyte in the sample medium. As an example case, the solid phase poly(dimethylsiloxane) (PDMS) is exposed to an aqueous dispersion containing silica nanoparticles with 10-nm radius. Confocal laser microscopic data show that these SiO2 nanoparticles do enter the PDMS and partition between the sample solution and solid phase. Moreover, they form aggregates at the surface of the solid phase. The overall partitioning of the SiO2 nanoparticles in the aqueous sample–PDMS system is examined and potential effects on the SPME analysis of organic analytes are indicated.