title: Multiresidue analysis of acidic and polar organic contaminants in water samples by stir-bar sorptive extraction-liquid desorption-gas chromatography-mass spectrometry.
abstract: The feasibility of stir-bar sorptive extraction (SBSE) followed by liquid desorption in combination with large volume injection (LVI)-in port silylation and gas chromatography-mass spectrometry (GC-MS) for the simultaneous determination of a broad range of 46 acidic and polar organic pollutants in water samples has been evaluated. The target analytes included phenols (nitrophenols, chlorophenols, bromophenols and alkylphenols), acidic herbicides (phenoxy acids and dicamba) and several pharmaceuticals. Experimental variables affecting derivatisation yield and peak shape as a function of different experimental PTV parameters [initial injection time, pressure and temperature and the ratio solvent volume/N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (MTBSTFA) volume] were first optimised by an experimental design approach. Subsequently, SBSE conditions, such as pH, ionic strength, agitation speed and extraction time were investigated. After optimisation, the method failed only for the extraction of most polar phenols and some pharmaceuticals, being suitable for the determination of 37 (out of 46) pollutants, with detection limits for these analytes ranging between 1 and 800 ng/L and being lower than 25 ng/L in most cases. Finally, the developed method was validated and applied to the determination of target analytes in various aqueous environmental matrices, including ground, river and wastewater. Acceptable accuracy (70-130%) and precision values (<20%) were obtained for most analytes independently of the matrix, with the exception of some alkylphenols, where an isotopically labelled internal standard would be required in order to correct for matrix effects. Among the drawbacks of the method, carryover was identified as the main problem even though the Twisters were cleaned repeatedly.
authors.affiliation: IUMA - University Institute of Environment, University of A Coruña, Pazo da Lóngora, Liáns, 15179 Oleiros (A Coruña), Spain.
authors.forename: José Benito
authors.initials: JB
authors.lastname: Quintana
authors.forename: Rosario
authors.initials: R
authors.lastname: Rodil
authors.forename: Soledad
authors.initials: S
authors.lastname: Muniategui-Lorenzo
authors.forename: Purificación
authors.initials: P
authors.lastname: López-Mahía
authors.forename: Darío
authors.initials: D
authors.lastname: Prada-Rodríguez
mesh_terms: D000085:Acetates / Q000737:chemistry; D002733:Chlorophenols / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D008970:Molecular Weight; D009930:Organic Chemicals / Q000032:analysis*; D015203:Reproducibility of Results; D052616:Solid Phase Extraction / Q000379:methods*; D013997:Time Factors; D014865:Waste Disposal, Fluid; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D000085:Acetates; D002733:Chlorophenols; D009930:Organic Chemicals; D014874:Water Pollutants, Chemical; D014867:Water; C007650:ethyl acetate