Determination of nitrophenols in environmental samples using stir bar sorptive extraction coupled to thermal desorption gas chromatography-mass spectrometry.

This paper presents a procedure for the determination of seven nitrophenols (NPs) in water and soil samples using stir bar sorptive extraction (SBSE) coupled to gas chromatography with mass spectrometry (GC-MS) by means of a thermal desorption unit (TDU). Microwave assisted extraction (MAE) is proposed to release the NPs from the soil matrices into an aqueous phase, prior to their acetylation. The different variables affecting the preconcentration efficiency of SBSE, during both the adsorption and the thermal desorption steps, are studied. As regards the analytical characteristics of the method, the accuracy was measured through recovery studies, recovery percentages in all cases being in the 79-120% range, as well as by analyzing a certified reference material. The precision was evaluated in terms of relative standard deviation, which provided values lower than 15% for both repeatability and reproducibility. The limits of detection were between 0.001 and 0.031 µg L-1 for water and 0.020-0.107 ng g-1 for soil samples. When environmental samples of different origins were analyzed, contents in the 0.01-1.0 µg L-1 and 0.7-40 ng g-1 ranges were obtained for waters and soils, respectively.