13 c bde 209

The concentration of 29 BDE congeners in liver samples collected at sacrifice were determined using gas chromatography/mass spectrometry operated in electron capture negative ionization mode (ECNI) as previously described^{94 (link)}. Samples were analyzed for nine congeners that comprise the DE-71 lot used as described^{17 (link)} (BDE-17, 28/33, -47, -85/155, -99, -100, -138, 153, -154) as well as -25, -30, -49, -66, -71, -75, -116, -119, -156, -181, -183, -190, -191, -200/203, -205, -206, -209 that are commonly monitored in the environment. There are only 6 congeners that make up the great majority (96%) of the DE-71 mixture used here: BDE-99 > -47 > -100 > -153 > -154 > -85 that range from 45.0 to 2.54% w/w^{17 (link)}. Similarly, 5 of these are the most prevalent BDE congeners found in human tissues: BDE-28, -47, -99, -100, and -153^{95 (link)} (Center for Disease Control and Prevention, NHANES, 2015). Prior to extraction, two internal standards were spiked into the homogenized tissue, including a monofluorinated BDE congener (F-BDE-69; Accustandard Inc.) and isotopically labeled BDE-209 (¹³C BDE-209; Wellington Laboratories). BDE congeners were extracted from liver tissues (approximately 1 g) using sonication and an aliquot of the extract was used for gravimetric analysis of lipid content. The remaining extract was purified using a Florisil solid phase extraction cartridge. Extracts were spiked with a third standard, isotopically labeled chlorinated diphenyl ether (¹³C CDE-141; Wellington Laboratories) to measure recovery of the internal standards and then analyzed via gas chromatography mass/ spectrometry using ECNI with methane as a reagent gas as previously described. BDE concentrations are expressed as ng/g lipid weight. The method detection limit (MDL) was calculated using 3 times the standard deviation of the laboratory blanks and was equivalent to 0.5 ng/g lw. Recoveries of F-BDE-69 averaged 90.9% ± 6.9% while ¹³C BDE 209 averaged 106% ± 19%.