Simultaneous preconcentration of a wide variety of organic pollutants in water samples. Comparison of stir bar sorptive extraction and membrane-assisted solvent extraction.

Stir bar soptive extraction (SBSE) coupled to thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) and membrane-assisted solvent extraction (MASE) coupled to large volume injection-programmed temperature vaporisation-GC-MS (LVI-PTV-GC-MS) were optimised for the simultaneous determination of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), phthalate esters (PEs), nonylphenols (NPs), polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers (PBDEs) in water samples. In the case of SBSE-TD, variables affecting the extraction (extraction time, addition of sodium chloride or methanol and sample volume) and desorption (cryofocusing temperature, desorption time and temperature, vent pressure and desorption flow) were fitted for the simultaneous determination. The extraction solvent nature (n-hexane, cyclohexane, n-heptane, ethyl acetate, toluene, dichloromethane or cyclohexane:ethyl acetate mixtures), as well as the addition of methanol (0-30%) and sodium chloride (0-20%), the extraction temperature (30-60 degrees C), shaking speed (250-750 rpm) and extraction time (5-150 min) were studied for the simultaneous membrane-assisted preconcentration. Finally, PTV-LVI variables such as injection volume (100-600 microL), injection speed (10-40 microL s(-1)), vent pressure (0-12.7 psi), vent time (0.05-0.8 min), vent flow (30-80 mL min(-1)), cryofocusing temperature (20-70 degrees C), split flow (20-100 mL min(-1)) and split time (1-5 min) were optimised. The optimisation was carried out by means of experimental design approaches in most of the cases. Precision (approximately 3-19% for both SBSE-TD and MASE-LVI-PTV), accuracy (approximately 80-120% for both SBSE-TD and MASE-LVI-PTV), limits of detection (LoDs) (0.1-222 ng L(-1) for MASE-LVI-PTV and 0.03-20.4 ng L(-1) for SBSE-TD in dependence of substance) and linearity (from 25 ng L(-1) up to at least 500 ng L(-1) for both procedures) were established for both procedures. Finally, the developed methods were applied to the determination of the free concentrations of PAHs, PCBs, PEs, NPs, PBBs and PBDEs in natural water samples (estuarine water and sea water) from the Bilbao estuary (Northern Spain) and comparable results were obtained with both procedures.