Determination of polychlorinated dibenzo-p-dioxins and dibenzofurans and comparison of extraction methods for edible freshwater fish and frogs in South Korea by using a high-resolution GC/MS

Three different extraction methods were evaluated: Soxhlet extraction, accelerated solvent extractor extraction and alkali digestion with high-resolution gas chromatography/high-resolution mass spectrometry, for the analysis of edible freshwater fish and frogs. The recovery efficiencies for the different extraction methods were also compared. Using these extraction methods, the concentrations and spatial distributions of these compounds in freshwater fish and frogs ( n = 99), collected from 31 locations on four major river systems (Han, Nakdong, Kum and Youngsan) and two wetlands in South Korea, were examined. The concentrations of total polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in all the freshwater fish and frog samples were analysed. The toxic equivalency (TEQ) concentration of PCDD/Fs in fish ranged from 0 ( n. d.) to 1.309 pg I-TEQ g(-1) wet weight. Detailed concentrations for different types of fish were as follows ( pg I-TEQ g(-1) wet weight): 0 ( n. d.) -1.309 for crucian ( mean 0.331, n = 28), 0.004 - 0.743 for carp (0.244, n = 10), 0.004 - 0.592 for dace (0.198, n = 8), 0.187 - 0.400 for cornet fish (0.287, n = 3), 0.164 - 0.410 for Korean piscivorous chub (0.303, n = 6), 0.105 - 0.516 for bass (0.310, n = 2), 0.451 - 0.812 for mullet ( 0.631, n = 2), 0.082 for long-nosed barbell, 0.100 for common Korean bitterling and 0.995 for dark chub. The total TEQ concentration ranged from 0 (n.d.) to 1.258 pg I-TEQ g(-1) wet weight for the two kinds of frogs (n = 36) investigated: 0 ( n. d.) - 1.258 pg I-TEQ g(-1) ( mean 0.346, n = 29) for the bullfrog and from 0 ( n. d.) - 0.474 pg I-TEQ g(-1) (0.185, n = 7) for the mountain frog.