Enhanced Bioaccessibility Extraction (MEBE) of hydrophobic soil pollutants - Using a semipermeable membrane for separating desorption medium and acceptor solvent

Abstract

[eng] Bioaccessibility extractions are increasingly applied to measure the fraction of pollutants in soil, sedi-ment and biochar, which can be released under environmentally or physiologically relevant conditions.However, the bioaccessibility of hydrophobic organic chemicals (HOCs) can be markedly underestimatedwhen the sink capacity of the extraction medium is insufficient. Here, a novel method called"MembraneEnhanced Bioaccessibility Extraction"(MEBE) applies a semipermeable membrane to physically separatean aqueous desorption medium that sets the desorption conditions from an organic medium that servesas acceptor phase and infinite sink. The specific MEBE method combines HOC (1) desorption into a 2-hydroxypropyl-b-cyclodextrin solution, (2) transfer through a low-density polyethylene (LDPE) mem-brane and (3) release into ethanol, serving as analytical acceptor phase. The surface to volume ratiowithin the LDPE membrane is maximized for rapid depletion of desorbed molecules, and the capacityratio between the acceptor phase and the environmental sample is maximized to achieve infinite sinkconditions. Several experiments were conducted for developing, optimizing and pre-testing the method,which was then applied to four soils polluted with polycyclic aromatic hydrocarbons. MEBE minimizedsample preparation and yielded a solvent extract readily analyzable by HPLC. This study focused on theproof-of-principle testing of the MEBE concept, which now can be extended and applied to other samplesand desorption media.