Microwave-assisted extraction and dispersive liquid-liquid microextraction followed by gas chromatography-mass spectrometry for isolation and determination of polycyclic aromatic hydrocarbons in smoked fish
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A simple and efficient method was developed using microwave-assisted extraction (MAE) and dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry (GC-MS) for the extraction and quantification of 16 polycyclic aromatic hydrocarbons (PAHs) in smoked fish. Benzo[a]pyrene, chrysene and pyrene were employed as model compounds and spiked to smoked fish to assess the extraction procedure. Several parameters, including the nature and volume of hydrolysis, extracting and disperser solvents, microwave time and pH, were optimized. In the optimum condition for MAE, 1g of fish sample was extracted in 12mL KOH (2M) and ethanol with a 50:50 ratio in a closed-vessel system. For DLLME, 500μL of acetone (disperser solvent) containing 100μL of ethylene tetrachloride (extraction solvent) was rapidly injected by syringe into 12mL of the sample extract solution (previously adjusted to pH 6.5), thereby forming a cloudy solution. Phase separation was performed by centrifugation and a volume of 1.5μL of the sedimented phase was analyzed by GC-MS in select ion monitoring (SIM) mode. Satisfactory results were achieved when this method was applied to analyze the PAHs in smoked fish samples. The MAE-DLLME method coupled with GC-MS provided excellent enrichment factors (in the range of 244-373 for 16 PAHs) and good repeatability (with a relative standard deviation between 2.8 and 9%) for spiked smoked fish. The calibration graphs were linear in the range of 1-200ngg -1 , with the square of the correlation coefficient (R 2 ) > 0.981 and detection limits between 0.11 and 0.43ngg -1 . The recoveries of those compounds in smoked fish were from 82.1% to 105.5%. A comparison of this method with previous methods demonstrated that the proposed method is an accurate, rapid and reliable sample-pretreatment method that gives very good enrichment factors and detection limits for extracting and determining PAHs from smoked fish. © 2012 Elsevier B.V..