High temperature water extraction combined with solid phase microextraction

Abstract

Solid phase microextraction (SPME) was coupled with high temperature water extraction for the determination of non-polar semivolatile compounds in solid matrices. Two different SPME approaches, dynamic and static, are described. In the dynamic extraction technique, analytes leached by hot water from a matrix were collected in a vial and simultaneously extracted from the water with SPME fibre. The collection vial was cooled using a bath to avoid analyte loss by evaporation. The optimized method using water extraction and SPME allowed quantitation based on external calibration with polycyclic aromatic hydrocarbons (PAHs) extracted from spiked sand. In the static approach, the water extraction of solids was performed using a high pressure cell with an SPME fibre inserted in the vessel. During the extraction process analytes were released from the matrix and then partitioned into the fibre coating as the cell was cooling down. In this technique isotopically labeled analogs of target analytes were used to compensate for the partial re-adsorption of analytes on the solid matrix at lower temperatures. The effects of different experimental conditions on the static high temperature water–SPME fibre extraction of NIST certified reference material, urban air particulates, were investigated. For quantitation the SPME fibre was removed from the collection water or the high pressure cell, and was immediately transferred to a gas chromatograph injection port to analyse extracts without any clean-up or pre-concentration. Both methods enable the determination of PAHs in solid matrices without use of organic solvent. Static high temperature water–SPME has an additional advantage since it does not require a high pressure pumping system.