Water Soxhlet Extraction Assisted by Focused Microwaves:  A Clean Approach

A prototype of a Soxhlet extractor that enables the use of water as extractant and application of focused microwaves on the cartridge zone has been designed and checked. The approach consists of a single unit in which the shortening of the distillation glassware allows reception of the water vapor in a refrigerant connected to the top of the sample cartridge vessel, its condensation, and dropping on the solid sample. When the water into the cartridge has reached a given level, irradiation with focused microwaves during an optimized time accelerates the leaching of the target analytes. Then, a valve is actuated and the extract is driven to the distillation flask where the leached species are concentrated as new vapor is formed and sent to the refrigerant and then to the cartridge. This new hybrid discontinuous−continuous approach has been used for leaching acid herbicides from different types of soil. The time required for total removal of the target compounds was 48 min. A flow injection manifold made posible the integration of the subsequent steps (preconcentration, chromatographic separation, UV detection) for the determination of the analytes, the recoveries of which range from 105.24 to 96.44%.