Approach for independent-matrix removal of polycyclic aromatic hydrocarbons from solid samples based on microwave-assisted Soxhlet extraction with on-line fluorescence monitoring

A flow injection interface for fluorometric monitoring of focused microwave-assisted Soxhlet extraction (FMASE) is presented. This assembly allows real-time on-line monitoring of the PAHs extracted from solid samples in each Soxhlet cycle and provides qualitative and semi-quantitative information from natural and spiked samples. Hence, the extraction kinetics can be followed and the end of the leaching step determined independently of the sample matrix, thus avoiding excessive extraction times. The research also involves the study of the multivariate effects of the FMASE parameters by a central composite design. The method was applied to a certified reference material (CRM 524, BCR, industrial soil/organics) for quality assurance/validation. The total content of each analyte was determined by HPLC-fluorometric detection, and the results obtained demonstrated that FMASE is a technique as efficient as conventional Soxhlet to extract PAHs from soils but with a drastic reduction of both extraction time and organic solvent disposal.