FIG. 2.

Mass spectra of identified metabolites of anaerobic p-ethylphenol degradation and their 2,3,5,6-d₄-isotopomers derived from 2,3,5,6-d₄-p-ethylphenol utilization. (A) Benzoic acid methyl ester. (B) 2,3,5,6-d₄-Benzoic acid methyl ester (please note that the MS evidence demonstrates four d atoms on the aromatic ring but does not necessarily prove the depicted labeling pattern). (C) p-Hydroxyacetophenone. (D) 2,3,5,6-d₄-p-Hydroxyacetophenone. (E) p-Hydroxybenzoic acid methyl ester. (F) 2,3,5,6,-d₄-p-Hydroxybenzoic acid methyl ester.