Sample Pretreatment Method for Determination of Indicator Polychlorinated Biphenyls in Seafood using Ultrasonic...

A simple, rapid and novel method has been developed and validated for the determination of seven indicator polychlorinated biphenyls (PCBs) in seafood samples by gas chromatography coupled to electron capture detector. Freeze-dried samples were done first ultrasonic extraction by n-hexane:methylene chloride:acetone (3:1:1, v/v), and then one-step clean-up (dispersive solid-phase extraction clean-up) or two-step clean-up (concentrated sulfuric acid purification and dispersive solid-phase extraction clean-up) was selected according to the lipid contents of the samples, if the lipid content was no more than 1%, one-step clean-up was used, otherwise, two-step clean-up was chose. The linearity of this method ranged from 1.25 to 100 μg/L, with regression coefficients ranging between 0.9991 and 0.9998. The limits of detection were in low ng/g level, ranging between 0.005 and 0.0076 ng/g (wet weight). The recoveries of spiked seven PCBs with external calibration method at different concentration levels in Pseudosciaena polyactis, Penaeus vannamei and Sinonovacula constricta were in the range of 78-105%, 73-110% and 75-107%, respectively, and with relative standard deviations of 3.3-5.1%, 3.5-6.3% and 3.4-5.1% (n = 5), respectively. The performance of the proposed method was also compared with traditional soxhlet extraction and column chromatography clean-up on the same real seafood samples and comparable efficiencies were obtained. It is concluded that this method can be successfully applied for the determination of PCBs in different seafood samples.