Validation of a method for the analysis of PAHs in bulk lake sediments using GC-MS

This work presents the validation procedures of an analytical method to determine the 16 PAHs from the US EPA's priority pollutants list in sediment samples using ultrasonic extraction coupled to gas chromatography-mass spectrometry. The extraction techniques are altered by the construction of an extraction flask adapted to the ultrasonic bath that greatly reduces losses and increases extraction efficiency of the volatile compounds, especially naphthalene. Cleanup procedures are also altered to change the polarity of the solvent mixture that contributes to reducing the elution of undesirable compounds. The PAH spiked sediment at 100 microg/kg level shows recovery rate of 68% to 108%. A certified reference material has been analyzed for those compounds showing results conforming to certified values. The optimized procedure is applied to sediment samples from different areas across Southeast Brazil and presents the results from the Ibirité Reservoir (MG, Brazil), a eutrophic water body. The total PAH concentration in these sediment samples varies between 103.96 and 180.87 microg/kg (dry weight). As the detected concentrations are relatively low, the acute toxicity detected in sediment and its pore water is not due to these compounds, but to high concentrations of ammonia, copper, and nickel according to TIE procedures.