Characterization of new bacterial transformation products of 1,1,1-trichloro-2,2-bis-(4-chlorophenyl) ethane (DDT) by gas chromatography/mass spectrometry

Abstract

The microbial transformation of DDT, DDD and DDE was studied in Gram‐negative strain B‐206 and a number of phenolic metabolites were identified as the trimethylsilyl derivatives in the bacterial extracts by gas chromatography/mass spectrometry. The major metabolites of DDT were DDD, DDE, DDMU, 1,1,1‐trichloro‐2‐(2‐hydroxy‐4‐chlorophenyl)‐2‐(4′‐chlorophenyl) ethane, 1,1,1‐trichloro‐2‐(2‐hydroxy‐4‐chlorophenyl)‐2‐(4′‐hydroxy phenyl) ethane, and 1,1,1‐trichloro‐2,2‐bis‐(2‐hydroxy‐4‐chlorophenyl) ethane. Conversely, DDD was mainly degraded into DDE, 1,1‐dichloro‐2‐(2‐hydroxy‐4‐chlorophenyl)‐2‐(4′‐cholorophenyl) ethane and 1,1‐dichloro‐2‐(2‐hydroxy‐4‐chloropheyl)‐2‐(4′‐hydroxyphenyl) ethane. Finally, DDE was transformed into DDMU, 1,1‐dichloro‐2‐(2‐hydroxy‐4‐chlorophenyl)‐2‐(4′‐chlorophenyl) ethylene, 1,1‐dichloro‐2‐(2‐hydroxy‐4‐chlorophenyl)‐2‐(4′hydroxyphenyl) ethylene and 1‐chloro‐2‐(2‐hydroxy‐4‐chlorophenyl)‐2‐(4′‐chlorophenyl) ethylene. The phenolic metabolites exhibited [M – TMSCl]^+., [M – HCl – TMSCl]^+. and/or [M – HCl – TMSCl – Me]⁺ fragment ions which reflect the presence of an ortho hydroxyl group in these molecules. Other mass spectral features used to determine their struture are presented and a metabolic scheme accounting for their formation is proposed.