Filtern
Erscheinungsjahr
- 2016 (3) (entfernen)
Dokumenttyp
- Posterpräsentation (2)
- Vortrag (1)
Sprache
- Englisch (3)
Referierte Publikation
- nein (3)
Schlagworte
- Pesticides (3) (entfernen)
Eingeladener Vortrag
- nein (1)
The occurrence of persistent organic pollutants like polychlorinated biphenyls (PCB) and organochlorine pesticides (OCP) in the environment is still a matter of concern, even years after their use was abolished. Hence, threshold values are regulated by law which reference a number of national and international standards for determination of said contaminants. In this context, soil is an especially difficult matrix, because several defining parameters can vary in a wide range. Organic matter content in particular has a crucial influence on extractability of contaminants because it largely governs formation of non-extractable or bound residues.
For this study, four soils of different total organic carbon (TOC) content were generated from uncontaminated reference soil (RefeSol 01-A) and compost which were spiked to contaminant levels representative of the Bundes-Bodenschutz-Verordnung (BBodSchV). These test materials were extracted using accelerated solvent extraction (ASE), Soxhlet extraction, and liquid-liquid extraction. For the latter method, samples were initially extracted for 15 minutes employing acetone. The follow-up extraction step was carried out using cyclohexane and the extraction time varied between 15 minutes and 16 hours. After clean-up, extracts were analysed via gas chromatography-mass spectrometry (GC MS) and with a gas chromatograph equipped with an electron capture detector (GC ECD).
Statistical analysis of the experimental values showed that recovery was not dependent on matrix TOC content. Also, no clear preference for a single method could be detected. Concerning liquid-liquid-extraction, it is merely observed that prolonged extraction time results in slightly higher recoveries, while moderate extraction times appear to yield the most robust results. Although Soxhlet and ASE show high recoveries, they also lead to larger standard deviations and are not suitable for determination of thermolabile pesticides.
In addition to recovery by different extraction methods, the agreement of values obtained by ECD and MS was evaluated. For ECD, standard deviations are generally higher but overall the values obtained by MS and ECD are comparable.
Metabolic transformation products of pesticides by electrochemical cell coupled to LC-MS (EC-LC-MS)
(2016)
Metabolic transformation products (TPs) of the insecticide chlorpyrifos (CPF), the new fungicide fluopyram (FLP) and the broad-spectrum herbicide, glyphosate (GLP), were studied by electrochemistry coupled to mass spectrometry (EC-MS) for the first time. Phase I metabolites of the three pesticides from rat liver in-vitro assay experiments were studied by LC-MS/MS and compared to electrochemically oxidized products from EC-MS.
Known metabolites from S-oxidation, O-dealkylation and hydroxylation of the insecticide chlorpyrifos have been identified by EC-MS and simulated to in-vitro assays. Chlorpyrifos-oxon (CPF-oxon), diethylthiophosphate (DETP), 3,5,6-trichloropiridinol (TCP), diethylphosphate (DEP) and 2,3,5-trichloropyridine (TCPy) were the main EC oxidative TPs and in-vitro assay metabolites of CPF which was also reported by Choe et al.. Fluopyram was extensively converted to a number of electrochemical products including mono- and dihydroxylated derivatives and yet unidentified TPs. Rat liver microsomal assay experiments showed mainly hydroxylated metabolites of FLP which was also reported by the European Food Safety Agency (EFSA). Aminomethyl phosphonic acid (AMPA) was the main TP of glyphosate detected from both EC-MS analysis and in-vitro assay tests.
A number of TPs of CPF, FLP and GLP have been identified by electrochemistry online mass spectrometry and compared to in-vitro assays. Using electrochemistry upfront MS enables fast and matrix free prediction of metabolic pathways, transformation products and/or fate of pesticides. Further studies will focus on structural characterization of detected compounds, phase II metabolites and investigation of real samples.
Among major food contaminants agrochemicals (including insecticides, fungicides and herbicides) are a threat for food safety in many countries. Once they entered the food chain or the environment, the parent compound can be transformed into different products by manmade and natural processes. The transformation products (TPs) might be more toxic and stable than the parent compound. In addition to this the transformation products might undergo conjugation with different compounds and/or changed to phase II metabolites.
Conventional in-vivo or in-vitro methods to study phase I and II metabolism have drawbacks of long-time sample preparation and matrix complexity. Online coupling of an electrochemical cell with liquid chromatography-mass spectrometry (EC–LC–MS) is a promising technique to study metabolites, fate and transformation products of pesticides. The new approach enables to identify metabolic transformation products by oxidizing analyte of interest on the EC, separate the metabolites on HPLC and identifying them by MS.
The aim of the present study is to identify/mimic pesticides phase I metabolites using electrochemical cell coupled to liquid chromatography-mass spectrometry (EC-LC-MS). Metabolic transformed products of two model compounds, fluopyram (fungicide) and chlorpyrifos (insecticide) were studied by EC upfront with MS. The results of EC-LC-MS are compared and discussed with those derived from in-vitro assays and the metabolites identified by LC-MS/MS.