Field-based supercritical fluid extraction and immunoassay for determination of PAHs in soils

A field-compatible supercritical-fluid extraction (SFE) device and method for extraction of organic contaminants from soil has been developed and combined with field-based immunoassay for on-site PAH (polycyclic aromatic hydrocarbon) determination. The optimised extraction method was tested in field experiments on natural samples with varying water content (0-32% w/w) without any sample pretreatment, yielding an average PAH recovery of 80% versus Soxhlet. The immunoassay functioned in buffer-diluted 10% v/v MeOH SFE extracts, allowing direct determination of PAHs with minimum sample manipulation. Immunoassay served as a reliable semi-quantitative technique for rapid screening of PAHs in SFE preparations of natural samples extracted in the field. Poor performance of the commercial solvent-shake extraction (SSE) method further supported the on-site SFE/immunoassay method.