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The effect of different storage conditions on the stability of 21 organic compounds selected from the EU list of priority substances in the field of water policy was investigated after their sorption from water onto polydimethylsiloxane-coated stir bars. After stir bar sorptive extraction (SBSE) of a model aqueous solution the stir bars were placed into glass thermal desorption tubes, closed with locking cones and stored a) at 25 °C and day light, b) in a refrigerator in dark at 4 °C, and c) in a freezer at -22 °C in dark during different time periods up to 8 weeks. Maximum holding times obtained for storage at laboratory temperature showed that no significant loss of any analyte occurred up to 4 days of storage. The storage of loaded stir bars in the refrigerator and freezer prolonged the maximum holding times to at least 24 and 40 days, respectively. The evaluation of stability was precluded for chlorfenvinphos and p,p'-DDT due to a poor method precision achieved in the test. In general, SBSE has been confirmed to be a suitable technique for analyte preservation when storage of samples prior to analysis is required. [ABSTRACT FROM AUTHOR]

A rapid method is proposed for the determination of selected H₂SO₄ stable organic compounds-eight organochlorines (OCs; hexachloro-1,3-butadiene, pentachlorobenzene, hexachlorobenzene, hexachlorocyclohexane-HCH-isomers, heptachlor) and six polybrominated diphenyl ethers (PBDEs; BDE-28, 47, 99, 100, 153, 154)-in fish samples. In the method, a modified QuEChERS (quick, easy, cheap, effective, rugged and safe) sample preparation using pH-tuned dispersive liquid⁻liquid microextraction (DLLME) and H₂SO₄ digestion fish extract clean-up is followed by gas chromatography⁻triple quadrupole tandem mass spectrometry (GC⁻QqQ-MS/MS) analysis. The method was validated in terms of linearity, limits of the method, recovery, accuracy, analysis of standard reference material (NIST SRM 1946), and estimation of combined uncertainty of the measurement (top-down approach). For validation, chub composite samples were used, and subsequently, the method was successfully applied to analysis of real samples of eight fish species. Finally, the method passed the analytical Eco-Scale evaluation as "an acceptable green analysis method", and showed its advantages (simplicity, rapidity, low cost, high extract clean-up efficiency, good sensitivity) when compared to other reported QuEChERS based methods., Competing Interests: The authors declare no conflict of interest.