Comparison of SFE, Soxhlet and sonication for the extraction of organic contaminants from sandstone

Supercritical Fluid Extraction (SFE), Soxhlet and a fast sonication procedure were compared for the extraction of representative creosote contaminants with special attention for NSO compounds, from dried sandstone aquifer materials. Spiking levels were 0.2, 1 and 10 mg/kg for 2 PAHs, 3 phenols and 6 NSO compounds. The 0.2 mg/kg level cannot be determined with accuracy whatever the method. SFE showed recoveries higher than 100% in most cases and 0% for 2,3-benzofuran. This method could only be recommended for PAHs recovery at 10 mg/kg level. On the whole, sonication and Soxhlet gave similar results for phenols and PAHs while sonication showed higher recoveries for NSO compounds. The choice of extraction procedure must rely on procedural characteristics such as processing time, ease of use, number of sample, analyte concentration. Sonication, being much shorter than Soxhlet, was therefore recommended for the extraction of creosote contaminants from sandstone.