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  • Carbon and nitrogen isotope effects associated with the dioxygenation of aniline and diphenylamine.

Carbon and nitrogen isotope effects associated with the dioxygenation of aniline and diphenylamine.

Environmental science & technology (2012-09-29)
Sarah G Pati, Kwanghee Shin, Marita Skarpeli-Liati, Jakov Bolotin, Soren N Eustis, Jim C Spain, Thomas B Hofstetter
ABSTRACT

Dioxygenation of aromatic rings is frequently the initial step of biodegradation of organic subsurface pollutants. This process can be tracked by compound-specific isotope analysis to assess the extent of contaminant transformation, but the corresponding isotope effects, especially for dioxygenation of N-substituted, aromatic contaminants, are not well understood. We investigated the C and N isotope fractionation associated with the biodegradation of aniline and diphenylamine using pure cultures of Burkholderia sp. strain JS667, which can biodegrade both compounds, each by a distinct dioxygenase enzyme. For diphenylamine, the C and N isotope enrichment was normal with ε(C)- and ε(N)-values of -0.6 ± 0.1‰ and -1.0 ± 0.1‰, respectively. In contrast, N isotopes of aniline were subject to substantial inverse fractionation (ε(N) of +13 ± 0.5‰), whereas the ε(C)-value was identical to that of diphenylamine. A comparison of the apparent kinetic isotope effects for aniline and diphenylamine dioxygenation with those from abiotic oxidation by manganese oxide (MnO(2)) suggest that the oxidation of a diarylamine system leads to distinct C-N bonding changes compared to aniline regardless of reaction mechanism and oxidant involved. Combined evaluation of the C and N isotope signatures of the contaminants reveals characteristic Δδ(15)N/Δδ(13)C-trends for the identification of diphenylamine and aniline oxidation in contaminated subsurfaces and for the distinction of aniline oxidation from its formation by microbial and/or abiotic reduction of nitrobenzene.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Diphenylamine, ReagentPlus®, 99%
Sigma-Aldrich
Diphenylamine, ACS reagent, ≥99%
Supelco
Diphenylamine, PESTANAL®, analytical standard
Sigma-Aldrich
Diphenylamine, puriss. p.a., redox indicator, ACS reagent, reag. Ph. Eur., ≥98% (GC)
Supelco
Diphenylamine solution, certified reference material, 5000 μg/mL in methanol