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Stir membrane extraction: a useful approach for liquid sample pretreatment.

In this paper, a novel extraction approach based on the use of a polymeric membrane as the extraction medium is described. For this aim, an original unit which allows the magnetic stirring of the membrane during the extraction process has been designed, optimized, and practically evaluated. On one hand, the main variables affecting the extraction process such as the unit design, the stirring rate, the extraction time, the sample volume, and the elution conditions were deeply studied. Once optimized, a model analytical problem, the determination of polycyclic aromatic hydrocarbons in water samples, was selected for practical evaluation of the stir membrane extraction procedure. The method was characterized on the basis of its linearity, precision, and limits of detection. The novel approach was sensitive and precise enough for the detection of the target analytes in the low nanogram per liter range using 25 mL of sample. In fact, limits of detection ranged from 0.8 ng/L (fluoranthene) to 7.6 ng/L (benzo-anthracene) with relative standard deviations lower than 8%.