Efficient extraction of fuel oil hydrocarbons from wood

Sequential cold (room temperature) extraction from aged contaminated wood samples (southern yellow pine) with acetone followed by n-pentane (upon a 3-4 days of sample incubation with each solvent) yielded more than 90% analyte recovery for both ambient (natural moisture content) and water-submerged wood, significantly exceeding the recoveries obtained with one-step extraction using single solvents and/or their mixtures. By contrast, a much faster ultrasound/Soxhlet extraction led to a virtually complete analyte recovery while using a 1: 1 mixture of these two solvents. Evidence obtained indicates that a possible role for the first solvent, acetone (in addition to collection of loose analyte), is the removal of an aqueous barrier surrounding the strongly adsorbed hydrocarbon, thus enabling its extraction by the second (non-polar) solvent. For larger analyte concentrations (>60 mg n-hexadecane/g wood), the high-affinity binding sites became saturated (yielding 5-10 mg unrecovered analyte/g wood), and then a single solvent was sufficient for a near-quantitative extraction.