An environmentally friendly sample pretreatment system based on solid-phase microextraction (SPME) for the sensitive determination of bisphenol A (BPA), bisphenol S (BPS) and biphenol (BP) is described. Two derivatisation reactions to obtain volatile derivatives are compared. Derivatisation with acetic anhydride (AA) was performed in situ in a 5-mM Na2CO3/NaHCO3 buffer solution and analytes were extracted by direct immersion (DI) using a PA fibre (85 µm) at 90°C for 40 min with stirring at 1,500 rpm. For derivatisation with bis-(trimethylsilyl)trifluoroacetamide (BSTFA), the analytes were first extracted by DI using the PA fibre at 70°C for 40 min with stirring at 500 rpm. The fibre was then removed, dried in a nitrogen stream for 2 min and introduced into the headspace of BSTFA at 50°C for 30 s. After derivatisation, the analytes were desorbed in the injection port of the GC in the splitless mode at 280°C for 4 min. The separation was carried out by coupling gas chromatography with mass spectrometry in the selected ion monitoring mode, GC-MS(SIM). The method allowed the determination of the migrating levels of bisphenols found in food cans, and it was validated for linearity, detection and quantitation limits, selectivity, accuracy and precision. Detection limits ranged from 3 to 16 pg mL−1, depending on the compound, at a signal-to-noise ratio of 3. Recoveries obtained for spiked samples were satisfactory for all compounds. Levels of BPA were higher than those of BPS and the lowest contents were found for BP.
Gas chromatography–mass spectrometry Solid-phase microextraction On-fibre derivatisation Bisphenols Food cans
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The authors are grateful to the Spanish MEC (Project CTQ2009-08267/BQU) for financial support. N. Martínez-Castillo acknowledges a fellowship from Departamento de Formación del Personal Académico de la Universidad Centroccidental Lisandro Alvarado (Venezuela).