7 research outputs found
Quantitative Identification of Biogenic Nonextractable Pesticide Residues in Soil by <sup>14</sup>C‑Analysis
Quantification
of nonextractable residues (NER) of pesticides in
soil is feasible by use of radioactively labeled compounds, but structural
information on these long-term stabilized residues is usually lacking.
Microorganisms incorporate parts of the radiolabeled (<sup>14</sup>C−) carbon from contaminants into microbial biomass, which
after cell death enters soil organic matter, thus forming biogenic
nonextractable residues (bioNER). The formation of bioNER is not yet
determinable in environmental fate studies due to a lack of methodology.
This paper focuses on the development of a feasible analytical method
to quantify proteinaceous carbon, since proteins make up the largest
mass portion of bacterial cells. The test substance <sup>14</sup>C-bromoxynil
after 56 days forms more than 70% of NER in soil. For further characterization
of NER the amino acids were extracted, purified, and separated by
two-dimensional thin-layer chromatography (TLC). Visualization of
the <sup>14</sup>C-amino acids was performed by bioimaging, unambiguous
identification by GC-MS and LC-MS/MS. Our analysis revealed that after
56 days of incubation about 14.5% of the <sup>14</sup>C-label of bromoxynil
was incorporated in amino acids. Extrapolating this content based
on the amount of proteins in the biomass (55%), in total about 26%
of the NER is accounted for by bioNER and thus is not environmentally
relevant