|Reddy, C.M., Xu, L., O'Neil, G.W., Nelson, R.K., Eglinton, T.I., Faulkner, D.J., Norstrom, R., Ross, P.S., Tittlemier, S.A., Radiocarbon evidence for a naturally-produced, bioaccumulating halogenated organic compound., Env. Sci. and Technol., 2004; v38, 1992-1997.|
Halogenated org. compds. (HOCs) such as 1,1'-dimethyl-3,3',4,4'-tetrabromo-5,5'-dichloro-2,2'-bipyrrole (DBP-Br4Cl2) and heptachloro-1'-methyl-1,2'-bipyrrole (Q1) have been detected worldwide, sometimes at high levels in Antarctic air, seabird eggs, the blubber of marine mammals, and, most notably, even human milk. To date, it has been difficult to det. whether these compds. are natural products or derived from industrial synthesis. Mol.-level 14C anal. of these compds. is particularly appealing because most industrial compds. are manufd. from petrochems. (14C-free) and natural compds. should have "modern" or "contemporary" 14C levels. To investigate the source of DBP-Br4Cl2, the authors isolated 600 mg of this compd. (150 mg of carbon) from marine animal exts. by employing gel permeation chromatog., Florisil column chromatog., and two-dimensional preparative capillary gas chromatog. The purified DBP-Br4Cl2 was split into two samples (75 mg of carbon each) and analyzed by accelerator mass spectrometry for 14C content. The D14C values were -449.permill. and -467.permill., corresponding to conventional 14C ages of 4740 and 5000 yr before present (BP), resp. The presence of detectable 14C in the DBP-Br4Cl2 strongly points to at least a natural or biogenic source. However, these D14C values for DBP-Br4Cl2 are more depleted than expected for a recently synthesized natural product. Several explanations are discussed, but addnl. samples from discrete locations need to be analyzed before a clear understanding of the source (or sources) of this compd. (and other unknown HOCs) is fully detd.