Optimization by factorial design of focused microwave assisted extraction of polycyclic aromatic hydrocarbons from marine sediment

The Focused Microwave (FMW) assisted extraction for organic contaminant ana lysis, such as polycyclic aromatic hydrocarbons (PAHs), in environmental ma trices, was studied and optimized using a factorial design. The effects and interactions of five parameters on the extraction recovery were investigat ed in a few experiments with a good accuracy: irradiation power and time, v olume and nature of solvent, and percentage of moisture of the matrix. The results show that the percentage of water added to the freeze-dried mat rix can significantly increase the extraction recovery. The irradiation pow er has also a positive effect. The choice of solvent is significant: a mixt ure of heptane/ethanol (80/20, v/v) allows better results than dichlorometh ane. Some interactions between percentage of moisture and the two previous parameters have been demonstrated: the effect of power and nature of solven t depends on the water content. Some optimal conditions have been establish ed: 10 mt of heptane/ethanol (80/20, v/v), extraction time of 2 min, and di fferent possible pairs of moisture content and irradiation power (140 W and 0% of moisture or 20 W and 40% of moisture) according to the need and wish of the experimentalist; or 10 mt of dichloromethane, extraction time of 2 min, 20 W and 40% of moisture. These optimized conditions provide very good recoveries compared to convent ional extraction such as Soxhlet (near 100%) for the model matrix (a marine sediment) used for the factorial design. FMW extraction is a good alternat ive to Soxhlet extraction with reduction of time and reduction of solvent v olume. This study show's that it is possible to substitute chlorinated solv ent by a less toxic solvent, like a mixture of heptane and ethanol.