The Complex Analysis of Chloroparaffins

Mass spectrometry is a powerful analytical method for the absolute determination of practically any chemical compound. The related spectra provide compositional as well as structural information. This wealth of valuable information benefits from instrumental and data-treatment achievements to enhance the mass-to-charge resolution as well as the detection power.
High resolution mass spectrometry for understanding hazardous pollutants

Persistent organic pollutans (POPs) are hazardous for the environment and living beings. The main research subject is to monitor POPs and investigate their potential transformation processes. Knowledge about transformation processes of these toxic, bioaccumulating and persistent compounds is important to understand their behavior in materials and environment. We do not shy away to investigate these contaminants under real processes be it metal drilling or in living bacterial cultures. To facilitate this research, we develop and apply state of the art analysis methods.

Abundances of the investigated contaminants are usually very low (ppm to ppb range), therefore sensitive analysis methods need to be applied. Our method of choice is high resolution mass spectrometry, which is a versatile technique to investigate composition of materials. First molecules or atoms are made to carry a charge to form ions. The mass of these ions in relation to the charge they carry are measured by a detector. Other substances than expected analytes in matrices can interfere. Instrumentations with highest resolutions can resolve these interferences. These mass spectra contain lots of information and their evaluation is demanding. Self-developed data processing tools help us to master the flood of information. We combine state of the art instrumentation and data evaluation methods to provide knowledge about hazardous contaminants. With the help of our mass spectrometric methods, we can prove that some transformation processes of persistent contaminants exist. 

Transformation of short-chain chlorinated paraffins by the enzyme LinB
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Figure 1: Schematic representation of the transformation of short-chain chlorinated paraffins catalyzed by LinB. Chloride (green) is substituted by a hydroxygroup (blue) forming mono- and di-hydroxylated transformation products.

In this study, the players short-chain chlorinated paraffins (SCCPs) and the enzyme LinB play the key roles (figure 1). SCCPs are polyhalogenated n-alkanes with carbon chain-lengths of C10-C13. LinB is an enzyme from the Sphingomonadacea bacteria family and catalyzes the substitution of halides with hydroxy-groups. We hypothe-sized that LinB may transform SCCPs into hydroxylated transformation products. To test this hypothesis, we exposed chlorinated tridecans (chlorinated C13-alkanes) to isolated LinB. The analysis was done on a quadrupole time of flight (QToF) device coupled to a soft-ionization source (APCI) with a liquid chromatographic (LC) prese-peration (LC-APCI-QToF-MS). Mass spectrometric interferences with impurities contained in the starting material could be mathematically resolved with a self-developed deconvolution procedure. Indeed, could we show that LinB catalyzes the transformation of chlorinated tridecanes to chlorinated tridecanols. These substances may also form in the environment under LinB-alike reactions.

References

Knobloch, M. C.; Schinkel, L.; Schilling, I.; Kohler, H. P. E.; Lienemann, P.; Bleiner, D.; Heeb, N. V. Transformation of short-chain chlorinated paraffins by the bacterial haloalkane dehalogenase LinB – Formation of mono- and di-hydroxylated metabolites. Chemosphere 2021, 262, 128288 (13 pp.). https://doi.org/10.1016/j.chemosphere.2020.128288
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Heeb, N. V.; Iten, S.; Schinkel, L.; Knobloch, M.; Sprengel, J.; Lienemann, P.; Bleiner, D.; Vetter, W. Characterization of synthetic single-chain CP standard materials - removal of interfering side products. Chemosphere 2020, 255, 126959 (8 pp.). https://doi.org/10.1016/j.chemosphere.2020.126959
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Schinkel, L.; Lehner, S.; Knobloch, M.; Lienemann, P.; Bogdal, C.; McNeill, K.; Heeb, N. V. Transformation of chlorinated paraffins to olefins during metal work and thermal exposure – Deconvolution of mass spectra and kinetics. Chemosphere 2018, 194, 803-811. https://doi.org/10.1016/j.chemosphere.2017.11.168
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