Solid-phase microextraction with simultaneous oxidative sample treatment for the sensitive determination of tetra- to hexa-brominated diphenyl ethers in sediments.
Solid-phase microextraction (SPME) is an effective technique for the extraction of polybrominated diphenyl ethers (PBDEs) from environmental water samples. Although it has been also applied to sediments, the organic content of this matrix causes an exponential decrease in the yield of the extraction. This work presents an improved SPME procedure for the sensitive determination of six PBDEs (tetra- to hexa-brominated congeners) in sediments containing up to 6% of total organic carbon (TOC). Samples (0.25-0.5g) were accurately weighed in 22mL glass vessels, mixed with a given amount of potassium permanganate, 0.5mL of sulphuric acid and 5mL of water. Extractions were performed at 100 degrees C, for 40min, using a polyacrylate (PA) coated fibre in the headspace (HS) mode. Potassium permanganate showed a dramatic, positive effect on the yield of the extraction. Its optimum amount was related to the TOC of the sediment, with overall highest responses attained for 40mg of oxidant per mg of organic carbon in the SPME vessel. Under final working conditions, the combination of SPME with gas chromatography coupled to tandem mass spectrometry (GC-MS/MS) provided relative standard deviations (RSDs) below 14%, relative recoveries from 76 to 111% and limits of quantification (LOQs) lower than 0.15ngg(-1) for all the investigated PBDEs in spiked river and marine sediments with different TOC. The performance of the method was also evaluated satisfactorily with a medium complexity (TOC 6.7%), real-life polluted sediment, previously analyzed in inter-laboratory comparison exercises.