Issue 3, 2023

Silylation: a reproducible method for characterization of non-extractable residues (NER) of organic chemicals in the assessment of persistence

Abstract

Most, if not all, chemicals, biocides, pharmaceuticals and pesticides are known to produce non-extractable residues (NER) in solid environmental media like soil and sediment during degradation testing to various extents. Since it has been found that parent substances and relevant metabolites can be contained and potentially released from NER there is currently much debate on how to include NER in the environmental persistence assessment. Using radioactive or stable isotope labelled test substances, three types of NER can be experimentally discriminated: entrapped, sorbed or heavily sorbed (type I) having the potential to be released from the matrix. Type II NER, i.e. residues covalently bound to organic matter in soils or sediments, are being considered to have very low remobilisation potential. Type III NER (bioNER) are formed after degradation of the xenobiotic chemical and incorporation into natural biomolecules (anabolism) like amino acids and other biomass compounds, and are, thus, of no environmental concern. Silylation has been suggested as a methodology to differentiate types I and II NER but concern has been addressed that this procedure is not suitable for routine analysis, e.g. in the context of studies for authorisation and registration of chemicals. Here, we describe a readily applicable and reproducible experimental procedure to apply this method for the analysis of NER derived from bromoxynil, sulfadiazine and isoproturon, respectively. This method is able to distinguish between heavily sorbed and covalently bound residues of chemicals, biocides, pharmaceuticals and pesticides in soils and to subsequently identify residues of the parent substance entrapped in type I NER.

Graphical abstract: Silylation: a reproducible method for characterization of non-extractable residues (NER) of organic chemicals in the assessment of persistence

Supplementary files

Article information

Article type
Paper
Submitted
13 Dec 2022
Accepted
12 Jan 2023
First published
20 Jan 2023
This article is Open Access
Creative Commons BY license

Environ. Sci.: Adv., 2023,2, 424-432

Silylation: a reproducible method for characterization of non-extractable residues (NER) of organic chemicals in the assessment of persistence

D. Hennecke, M. Kruse, J. Bräutigam, B. Meisterjahn, J. Klein, D. Claßen, S. Trapp, M. Kästner, A. L. Brock and A. Schäffer, Environ. Sci.: Adv., 2023, 2, 424 DOI: 10.1039/D2VA00314G

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