Paper supported polystyrene membranes for thin film microextraction

Thin film microextraction (TFME), which is based on the retention of target analytes in a thin polymeric coating, is a powerful sample treatment technique with multiple applications. This article describes an easy and cheap procedure to synthesize polystyrene membranes which can be used as sorptive phases in TFME. The polymeric film is formed by the simple deposition of a thin polymeric layer over a conventional laboratory paper that acts as inert support. The synthesis has been studied and the resulting material has been characterized by infrared spectroscopy and scanning electron microscopy. The thin film has been analytically evaluated using the determination of methadone in urine samples by gas chromatography/mass spectrometry (GC/MS) as proof of concept problem. A pipette tip manifold, that allows the confinement of the film while permits the sample and solvents handling, has been designed for the extraction. The developed method provides a good linearity (R2 = 0.9986) and sensitivity (limit of quantification of 10 μg/L), especially if the low sample volume (200 μL) used is considered. The precision (relative standard deviation better than 14%) and relative recovery values (average value of 106% for five independent samples) demonstrated the potential of the approach.