@inproceedings{hildebrandt_bestimmung_elementarer_2023, 
author={Hildebrandt, L. and Fensky, F. and Klein, O. and Zimmermann, T. and Pröfrock, D.},
title={Bestimmung elementarer Fingerabdrücke von Korrosionsschutzbeschichtungen mittels ICP-MS/MS als wichtiger Baustein für die Mikroplastikanalytik},
year={2023},
booktitle = {Wasser 2023 - Jahrestagung der Wasserchemischen Gesellschaft},
note = {Hildebrandt, L.; Fensky, F.; Klein, O.; Zimmermann, T.; Pröfrock, D.: Bestimmung elementarer Fingerabdrücke von Korrosionsschutzbeschichtungen mittels ICP-MS/MS als wichtiger Baustein für die Mikroplastikanalytik. In: Wasser 2023 - Jahrestagung der Wasserchemischen Gesellschaft. Augsburg (DEU), 15.05.2023 - 17.05.2023, 2023.}}
@inproceedings{klein_using_icpmsms_2023, 
author={Klein, O. and Zimmermann, T. and Hildebrandt, L. and Pröfrock, D.},
title={Using ICP-MS/MS in complex environments - spatial distribution and possible sources of technology-critical elements},
year={2023},
booktitle = {European Winter Conference on Plasma Spectrochemistry},
note = {Klein, O.; Zimmermann, T.; Hildebrandt, L.; Pröfrock, D.: Using ICP-MS/MS in complex environments - spatial distribution and possible sources of technology-critical elements. In: European Winter Conference on Plasma Spectrochemistry. Ljubljana (SVN), 29.01.2023 - 03.02.2023, 2023.}}
@inproceedings{ebeling_from_offshore_2023, 
author={Ebeling, A. and Wippermann, D. and Zonderman, A. and Zimmermann, T. and Klein, O. and Erbslöh, H. and Kirchgeorg, T. and Weinberg, I. and Pröfrock, D.},
title={From offshore wind to green Power-to-X products – how ICP-MS can help to monitor potential emerging chemical emissions},
year={2023},
booktitle = {European Winter Conference on Plasma Spectrochemistry 2023},
note = {Ebeling, A.; Wippermann, D.; Zonderman, A.; Zimmermann, T.; Klein, O.; Erbslöh, H.; Kirchgeorg, T.; Weinberg, I.; Pröfrock, D.: From offshore wind to green Power-to-X products – how ICP-MS can help to monitor potential emerging chemical emissions. In: European Winter Conference on Plasma Spectrochemistry 2023. Ljubljana (SVN), 29.01.2023 - 03.02.2023, 2023.}}
@article{hildebrandt_spatial_distribution_2022, 
author={Hildebrandt, L. and El Gareb, F. and Zimmermann, T. and Klein, O. and Kerstan, A. and Emeis, K. and Pröfrock, D.},
title={Spatial distribution of microplastics in the tropical Indian Ocean based on laser direct infrared imaging and microwave-assisted matrix digestion},
year={2022},
journal = {Environmental Pollution},
volume = {307},
pages = {119547},
doi = {10.1016/j.envpol.2022.119547},
abstract = {Suspended particulate matter was collected from subsurface (6 m) water along an E-W transect through the tropical Indian Ocean using a specialized inert (plastic free) fractionated filtration system. The samples were subjected to a new microwave-assisted “one-pot” matrix removal (efficiency: 94.3% ± 0.3% (1 SD, n = 3)) and microplastic extraction protocol (recovery: 95% ± 4%). The protocol enables a contamination-minimized digestion and requires only four filtration steps. In comparison, classical sample processing approaches involve up to eight filtration steps until the final analysis. Microplastics were identified and physically characterized by means of a novel quantum cascade laser-based imaging routine.

LDIR imaging facilitates the analysis of up to 1000 particles/fibers (<300 μm) within approximately 1–2 h. In comparison to FTIR and Raman imaging, it can help to circumvent uncertainties, e. g. from subsampling strategies due to long analysis and post-processing times of large datasets. Over 97% of all particles were correctly identified by the automated routine - without spectral reassignments. Moreover, 100% agreement was obtained between ATR-FTIR and LDIR-based analysis regarding particles and fibers >300 μm.

The mean microplastic concentration of the analyzed samples was 50 ± 30 particles/fibers m−3 (1 SD, n = 21). Number concentrations ranged from 8 to 132 particles/fibers m−3 (20–300 μm). The most abundant polymer clusters were acrylates/polyurethane/varnish (49%), polyethylene terephthalate (26%), polypropylene (8%), polyethylene (4%) and ethylene-vinyl acetate (4%). 96% of the microplastic particles had a diameter <100 μm. Though inter-study comparison is difficult, the investigated area exhibits a high contamination with particulate plastics compared to other open ocean regions. A distinct spatial trend was observed with an increasing share of the size class 20–50 μm from east to west.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.envpol.2022.119547} (DOI). Hildebrandt, L.; El Gareb, F.; Zimmermann, T.; Klein, O.; Kerstan, A.; Emeis, K.; Pröfrock, D.: Spatial distribution of microplastics in the tropical Indian Ocean based on laser direct infrared imaging and microwave-assisted matrix digestion. In: Environmental Pollution. Vol. 307 (2022) 119547. (DOI:  /10.1016/j.envpol.2022.119547)}}
@inproceedings{klein_technologiekritische_elemente_2022, 
author={Klein, O. and Zimmermann, T. and Ebeling, A. and Kruse, M. and Kirchgeorg, T. and Pröfrock, D.},
title={Technologie-kritische Elemente - Entwicklung und Anwendung einer ICP-MS/MS basierten Methode zur Messung ihrer zeitlichen Variationen in Nordsee Sedimenten },
year={2022},
booktitle = {Wasser 2022 - Jahrestagung der Wasserchemischen Gesellschaft},
note = {Klein, O.; Zimmermann, T.; Ebeling, A.; Kruse, M.; Kirchgeorg, T.; Pröfrock, D.: Technologie-kritische Elemente - Entwicklung und Anwendung einer ICP-MS/MS basierten Methode zur Messung ihrer zeitlichen Variationen in Nordsee Sedimenten . In: Wasser 2022 - Jahrestagung der Wasserchemischen Gesellschaft. Wiesbaden (DEU), 23.05.2022 - 25.05.2022, 2022.}}
@article{ebeling_analysis_of_2022, 
author={Ebeling, A. and Zimmermann, T. and Klein, O. and Irrgeher, J. and Pröfrock, D.},
title={Analysis of Seventeen Certified Water Reference Materials for Trace and Technology-Critical Elements},
year={2022},
journal = {Geostandards and Geoanalytical Research},
volume = {46},
number = {2},
pages = {351 - 378},
doi = {10.1111/ggr.12422},
abstract = {Concentrations of elements in the aquatic environment are a key parameter for various scientific fields such as biogeochemistry, biology and environmental science. Within this context, the scientific community asks for new analytical protocols to be able to quantify more and more elements of the periodic table. Therefore, the requirements for aqueous reference materials have increased drastically. Even though a wide variety of CRMs of different water matrices are available, certified values of many elements (e.g., rare earth elements, technology-critical elements, such as Ga and In, and generally those elements which are not part of current monitoring regulations) do not yet exist. Therefore, the scientific community relies on published elemental concentrations of many CRMs provided by other researchers. Some elements of interest, such as the rare earth elements, are well studied and plenty of literature values exist. However, less studied elements, such as Ga and In, are rarely studied. In this study, an 'externally' calibrated quantification method based on an optimised online pre-concentration method, coupled with ICP-MS/MS, is used for the quantification of thirty-four elements. The method is applied to seventeen water CRMs covering freshwater, brackish water and seawater. The measured data is combined with a comprehensive literature review on non-certified values in selected water CRMs and new consensus values are suggested for various non-certified elements.},
note = {Online available at: \url{https://dx.doi.org/10.1111/ggr.12422} (DOI). Ebeling, A.; Zimmermann, T.; Klein, O.; Irrgeher, J.; Pröfrock, D.: Analysis of Seventeen Certified Water Reference Materials for Trace and Technology-Critical Elements. In: Geostandards and Geoanalytical Research. Vol. 46 (2022) 2, 351 - 378. (DOI:  /10.1111/ggr.12422)}}
@article{klein_occurrence_and_2022, 
author={Klein, O. and Zimmermann, T. and Ebeling, A. and Kruse, M. and Kirchgeorg, T. and Pröfrock, D.},
title={Occurrence and Temporal Variation of Technology-Critical Elements in North Sea Sediments - A Determination of Preliminary Reference Values},
year={2022},
journal = {Archives of Environmental Contamination and Toxicology},
volume = {82},
number = {4},
pages = {481 - 492},
doi = {10.1007/s00244-022-00929-4},
abstract = {As interest in the investigation of possible sources and environmental sinks of technology-critical elements (TCEs) continues to grow, the demand for reliable background level information of these elements in environmental matrices increases. In this study, a time series of ten years of sediment samples from two different regions of the German North Sea were analyzed for their mass fractions of Ga, Ge, Nb, In, REEs, and Ta (grain size fraction < 20 µm). Possible regional differences were investigated in order to determine preliminary reference values for these regions. Throughout the investigated time period, only minor variations in the mass fractions were observed and both regions did not show significant differences. Calculated local enrichment factors ranging from 0.6 to 2.3 for all TCEs indicate no or little pollution in the investigated areas. Consequently, reference values were calculated using two different approaches (Median + 2 median absolute deviation (M2MAD) and Tukey inner fence (TIF)). Both approaches resulted in consistent threshold values for the respective regions ranging from 158 µg kg−1 for In to 114 mg kg−1 for Ce. As none of the threshold values exceed the observed natural variation of TCEs in marine and freshwater sediments, they may be considered baseline values of the German Bight for future studies.},
note = {Online available at: \url{https://dx.doi.org/10.1007/s00244-022-00929-4} (DOI). Klein, O.; Zimmermann, T.; Ebeling, A.; Kruse, M.; Kirchgeorg, T.; Pröfrock, D.: Occurrence and Temporal Variation of Technology-Critical Elements in North Sea Sediments - A Determination of Preliminary Reference Values. In: Archives of Environmental Contamination and Toxicology. Vol. 82 (2022) 4, 481 - 492. (DOI:  /10.1007/s00244-022-00929-4)}}
@inproceedings{elgareb_analyse_des_2022, 
author={El Gareb, F. and Hildebrandt, L. and Zimmermann, T. and Klein, O. and Kerstan, A. and Emeis, K. and Pröfrock, D.},
title={Analyse des Vorkommens und der Verteilung von Mikrokunststoffen im tropischen Indischen Ozean mittels Laser Direct Infrared (LDIR) Chemical Imaging und mikrowellenunterstützter Probenaufbereitung},
year={2022},
booktitle = {Wasser 2022 - Jahrestagung der Wasserchemischen Gesellschaft},
note = {El Gareb, F.; Hildebrandt, L.; Zimmermann, T.; Klein, O.; Kerstan, A.; Emeis, K.; Pröfrock, D.: Analyse des Vorkommens und der Verteilung von Mikrokunststoffen im tropischen Indischen Ozean mittels Laser Direct Infrared (LDIR) Chemical Imaging und mikrowellenunterstützter Probenaufbereitung. In: Wasser 2022 - Jahrestagung der Wasserchemischen Gesellschaft. Wiesbaden (DEU), 23.05.2022 - 25.05.2022, 2022.}}
@inproceedings{prfrock_icpmsms_and_2022, 
author={Pröfrock, D. and Hildebrandt, L. and El Gareb, F. and Nack, F. and Zimmermann, T. and Klein, O.},
title={ICP-MS/MS and LDIR as complementary technique in small micro- and nanoplastic Research - From method optimization to the study of environmentally relevant polymers as vector for trace metals},
year={2022},
booktitle = {Analytic Conference},
note = {Pröfrock, D.; Hildebrandt, L.; El Gareb, F.; Nack, F.; Zimmermann, T.; Klein, O.: ICP-MS/MS and LDIR as complementary technique in small micro- and nanoplastic Research - From method optimization to the study of environmentally relevant polymers as vector for trace metals. In: Analytic Conference. München (DEU), 21.06.2022 - 24.06.2022, 2022.}}
@article{klein_technologycritical_elements_2022, 
author={Klein, O. and Zimmermann, T. and Hildebrandt, L. and Pröfrock, D.},
title={Technology-critical elements in Rhine sediments - A case study on occurrence and spatial distribution},
year={2022},
journal = {Science of the Total Environment},
volume = {852},
pages = {158464},
doi = {10.1016/j.scitotenv.2022.158464},
abstract = {Despite their presence in almost every technical device, little is known about the occurrence, distribution, and fate of technology-critical elements (TCEs) within the environment. Due to high economic demands and short product lifespans as well as low recycling rates, many TCEs appear to become emerging contaminants.

Within the scope of this work, 57 sediment samples from the German part of the Rhine river, as well as various tributaries, were collected to study the occurrence and distribution of TCEs. This specific catchment area has consistently been subjected to strong anthropogenic influences over the last century. Hierarchical Cluster analysis, as well as principal component analysis were used to gain first insights into the spatial distribution and possible sources of TCEs along the Rhine.

Obtained mass fractions in conjunction with corresponding geoaccumulation indices (Igeo) provide first indications of a possible enrichment along the Rhine for the TCEs of interest (Ga, Ge, Nb, In, Te, rare earth elements, and Ta). Especially the mass fractions of Zn, Ge, In, La, Sm, and Gd exhibit significant anthropogenic inputs. For stations characterized by high Ge and In mass fractions, element fingerprints imply possible atmospheric deposition stemming from e.g. combustion processes. Distinct anomalies of La and Sm most likely originate from discharges located at the city of Worms into the Upper Rhine. Statistical analysis of all analyzed 55 elemental mass fractions revealed similar behavior of TCEs compared to classical heavy metals. Diffuse as well as point sources of TCEs are likely. As a result, this study provides further insight into the role of TCEs as potential emerging contaminants in the environment.},
note = {Online available at: \url{https://dx.doi.org/10.1016/j.scitotenv.2022.158464} (DOI). Klein, O.; Zimmermann, T.; Hildebrandt, L.; Pröfrock, D.: Technology-critical elements in Rhine sediments - A case study on occurrence and spatial distribution. In: Science of the Total Environment. Vol. 852 (2022) 158464. (DOI:  /10.1016/j.scitotenv.2022.158464)}}
@inproceedings{klein_erschlieung_der_2022, 
author={Klein, O. and Stefan Kremmler, T. and Zimmermann, T. and Pröfrock, D.},
title={Erschließung der „urbanen Miene“ – Entwicklung einer Aufschlussmethode für Leiterplatinen zur Bestimmung der Metallgehälter mittels ICP-MS/MS},
year={2022},
booktitle = {ICP-MS Anwender*innen Treffen},
note = {Klein, O.; Stefan Kremmler, T.; Zimmermann, T.; Pröfrock, D.: Erschließung der „urbanen Miene“ – Entwicklung einer Aufschlussmethode für Leiterplatinen zur Bestimmung der Metallgehälter mittels ICP-MS/MS. In: ICP-MS Anwender*innen Treffen. Leoben (AUT), 05.09.2022 - 08.09.2022, 2022.}}
@inproceedings{prfrock_more_than_2022, 
author={Pröfrock, D. and Przibilla, A. and Klein, O. and Hildebrandt, L. and Ebeling, A. and El Gareb, F. and Zimmermann, T.},
title={More than trace elements – New Applications for ICP-MS to investigate the chemical anthropocene},
year={2022},
booktitle = {28. ICP-MS Anwender*innentreffen und 14. Symposium massenspektrometrische Verfahren der Elementspurenanalyse},
note = {Pröfrock, D.; Przibilla, A.; Klein, O.; Hildebrandt, L.; Ebeling, A.; El Gareb, F.; Zimmermann, T.: More than trace elements – New Applications for ICP-MS to investigate the chemical anthropocene. In: 28. ICP-MS Anwender*innentreffen und 14. Symposium massenspektrometrische Verfahren der Elementspurenanalyse. Leoben (AUT), 05.09.2022 - 08.09.2022, 2022.}}
@inproceedings{zonderman_turbinecolonizing_mussels_2022, 
author={Zonderman, A. and Wippermann, D. and Ebeling, A. and Klein, O. and Erbslöh, H. and Zimmermann, T. and Pröfrock, D.},
title={Turbine-colonizing mussels (Mytilus edulis) as an indicator for environmental impacts of offshore wind farms in the North Sea},
year={2022},
booktitle = {YOUMARES 13},
note = {Zonderman, A.; Wippermann, D.; Ebeling, A.; Klein, O.; Erbslöh, H.; Zimmermann, T.; Pröfrock, D.: Turbine-colonizing mussels (Mytilus edulis) as an indicator for environmental impacts of offshore wind farms in the North Sea. In: YOUMARES 13. Berlin (DEU), 11.10.2022 - 14.10.2022, 2022.}}
@inproceedings{klein_enhanced_detection_2021, 
author={Klein, O. and Zimmermann, T. and Pröfrock, D.},
title={Enhanced detection of technologically critical elements in sediment digestions via ICP-MS/MS utilizing N2O as a reaction gas},
year={2021},
booktitle = {6. Doktorandenseminar des DAAS},
note = {Klein, O.; Zimmermann, T.; Pröfrock, D.: Enhanced detection of technologically critical elements in sediment digestions via ICP-MS/MS utilizing N2O as a reaction gas. In: 6. Doktorandenseminar des DAAS. Virtual, 20.09.2021 - 21.09.2021, 2021.}}
@article{klein_improved_determination_2021, 
author={Klein, O. and Zimmermann, T. and Pröfrock, D.},
title={Improved determination of technologically critical elements in sediment digests by ICP-MS/MS using N2O as a reaction gas},
year={2021},
journal = {Journal of Analytical Atomic Spectrometry},
volume = {36},
number = {7},
pages = {1524 - 1532},
doi = {10.1039/D1JA00088H},
abstract = {The investigation of technologically critical elements (TCEs) as emerging pollutants is a constantly growing field of environmental research and societal concern. Nevertheless, existing data for most TCEs are still unsatisfactory for an accurate assessment of their potential (eco)toxicological effects on humans and the environment. The limited availability of data mainly results from the technically challenging analysis of selected TCEs. Low concentrations of TCEs in environmental matrices (μg kg−1 or lower) and the associated complex and time-consuming sample preparation pose the greatest challenges. This work aims at developing a new ICP-MS/MS-based multi-elemental approach targeting the analysis of all major TCEs (Sc, Ga, Ge, Nb, In, Te, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Yb, Lu, and Ta) in sediment, which represents one of the most important matrices for environmental research. N2O is applied as a reaction gas to overcome possible spectral interferences during ICP-MS/MS analysis. The use of N2O as a reaction gas for ICP-MS/MS analysis enabled higher oxide-product ion yields for many TCEs in comparison to the frequently used O2 cell gas. Hence, the selectivity and sensitivity of the method were improved. The presented multi-element method using N2O as a reaction gas achieved LODs between 0.00023 μg L−1 (Eu) and 0.13 μg L−1 (Te) for all analyzed TCEs. Likewise, for all analyzed elements, except for Te, recoveries between 80% and 112% were obtained for at least one of the analyzed reference materials (GBW 07313, GBW 07311, and BCR-2).},
note = {Online available at: \url{https://dx.doi.org/10.1039/D1JA00088H} (DOI). Klein, O.; Zimmermann, T.; Pröfrock, D.: Improved determination of technologically critical elements in sediment digests by ICP-MS/MS using N2O as a reaction gas. In: Journal of Analytical Atomic Spectrometry. Vol. 36 (2021) 7, 1524 - 1532. (DOI:  /10.1039/D1JA00088H)}}
@misc{hildebrandt_fast_automated_2020, 
author={Hildebrandt, L. and El Gareb, F. and Zimmermann, T. and Klein, O. and Emeis, K. and Pröfrock, D. and Kerstan, A.},
title={Fast, Automated Microplastics Analysis Using Laser Direct  Chemical Imaging : Characterizing and quantifying microplastics in water samples from marine environments},
year={2020},
howpublished = {Other: Sonstiges;},
abstract = {It is estimated that more than 75% of the 8.3 billion metric tons of plastic produced over the last 65 years have turned into waste (1). Up to 13 million metric tons of this waste ends up in the ocean every year (2) and recent calculations estimate that more than 5.25 trillion plastic particles float in the world’s oceans (3). Scientists have demonstrated the alarming environmental ubiquity and persistence of particulate plastic in aquatic ecosystems (4). Models predict that approximately 14% of the plastic debris in the ocean surface layer can be classified as so-called microplastics (often referred to as particles between 1 μm and 5 mm in size) (5).  These ingestible and potentially harmful particles have been formed by UV-induced, mechanical, or biological degradation of larger debris items (6). To verify the estimates and to meet upcoming regulatory measures (e.g., California Senate  Bill 1422) and directives (MSFD, 2008/56/EC), accurate, time-efficient, and robust analytical workflows and techniques are required.},
note = {Hildebrandt, L.; El Gareb, F.; Zimmermann, T.; Klein, O.; Emeis, K.; Pröfrock, D.;  Kerstan, A.: Fast, Automated Microplastics Analysis Using Laser Direct  Chemical Imaging : Characterizing and quantifying microplastics in water samples from marine environments. 2020.}}
@inproceedings{zimmermann_nontraditional_stable_2020, 
author={Zimmermann, T. and Klein, O. and Reese, A. and Wieser, M. and Mohamed, F. and Irrgeher, J. and Pröfrock, D.},
title={“Non-Traditional” Stable Isotope Analysis as Tracer so Identify Sources and Sinks of Inorganic Contaminants in Riverine Environments},
year={2020},
booktitle = {Goldschmidt 2020},
doi = {10.46427/gold2020.3228},
abstract = {Environmental monitoring of complex ecosystems requires reliable and sensitive techniques in order to identify the source, fate and sink of inorganic, anthropogenic contaminants in e.g. aquatic ecosystems. 
This contribution presents large scale isotopic data of B, Zn, Sr, Nd and Pb, measured via MC ICP-MS, for water and sediment samples of two major Europaen rivers (Rhine, Elbe). The aim was to apply stable isotope analysis as new, potential tracer to elucidate processes involving anthropogenic metal emissions, as well as to characterize the catchment areas for further studies. 
Within this context we analyzed the Zn isotopic composition, to potentially trace anthropogenic Zn emission on a large regional scale. The combination of dissolved B and Sr isotopic compositions may be used to distinguish different inputs into river systems, and provide insight into possible sources of B inputs. Furthermore, Sr, Nd and Pb isotope data can give valuable information for source attribution of sediment masses 
Our results clearly indicate that the exclusive focus on the quantitative analysis of metal contamination within the context of environmental research provides only limited information. The progress achieved in isotope ratio analysis over the last decade therefore opens valuable additional information for environmental scientists.},
note = {Online available at: \url{https://dx.doi.org/10.46427/gold2020.3228} (DOI). Zimmermann, T.; Klein, O.; Reese, A.; Wieser, M.; Mohamed, F.; Irrgeher, J.; Pröfrock, D.: “Non-Traditional” Stable Isotope Analysis as Tracer so Identify Sources and Sinks of Inorganic Contaminants in Riverine Environments. In: Goldschmidt 2020. Virtual, 21.06.2020 - 26.06.2020, 2020. (DOI:  /10.46427/gold2020.3228)}}
@inproceedings{zimmermann_boron_and_2020, 
author={Zimmermann, T. and Klein, O. and Reese, A. and Irrgeher, J. and Pröfrock, D.},
title={Boron and strontium isotope ratio analysis of the Rhine river – tracer for anthropogenic boron emissions?},
year={2020},
booktitle = {53rd Annual Conference of the German Society for Mass Spectrometry DGMS including 27th ICP-MS User´s Meeting},
abstract = {Environmental monitoring of complex ecosystems requires reliable and sensitive techniques in order to identify the source, fate and sink of anthropogenic contaminants in e.g. aquatic ecosystems. Within this context, the analysis of stable isotope ratios has been proved a valuable tool. Amongst other applications, the analysis of B and Sr isotope ratios has evolved as promising tracer to differentiate water bodies of different origin and their corresponding mixing processes of e.g. freshwater and seawater.

Due to its versatile use in industries e.g. as sodium perborate, or more recently as dopant for semiconductors, analysis if boron isotope ratios may be of value as a new tracer for anthropogenic B emissions into the aquatic environment.

This contribution aims to investigate, whether it is possible to distinguish between the different discharges of a river on the basis of their B and Sr isotopic signatures, in order to distinguish between natural and human input sources of B into the aquatic environment. Therefore, 76 freshwater samples from one of the most anthropogenically influenced rivers in Germany, the Rhine, were analyzed for their Sr and B isotopic composition. The B isotope composition assessed in the Rhine River shows a large variability of δ11B/10BNIST951a of ca. 30‰, and a B concentration ranging from 11.6 µg L-1 ± 1.3 µg L-1 to 65 µg L-1 ± 6 µg L-1. In contrast to that. the Rhine tributaries are characterized by significantly higher B loads. Additionally, tributaries are characterized by Sr concentrations and Sr isotope ratios significantly different from those of the Rhine.

The combination of Sr and B isotopic compositions can be used to distinguish different inputs into a complex river system, and can therefore provide a better insight into possible sources and distribution of anthropogenic B inputs.},
note = {Zimmermann, T.; Klein, O.; Reese, A.; Irrgeher, J.; Pröfrock, D.: Boron and strontium isotope ratio analysis of the Rhine river – tracer for anthropogenic boron emissions?. In: 53rd Annual Conference of the German Society for Mass Spectrometry DGMS including 27th ICP-MS User´s Meeting. Münster (DEU), 01.03.2020 - 04.03.2020, 2020.}}
@article{zimmermann_substituting_hf_2020, 
author={Zimmermann, T. and von der Au, M. and Reese, A. and Klein, O. and Hildebrandt, L. and Pröfrock, D.},
title={Substituting HF by HBF4 – an optimized digestion method for multi-elemental sediment analysis via ICP-MS/MS},
year={2020},
journal = {Analytical Methods},
volume = {12},
number = {30},
pages = {3778 - 3787},
doi = {10.1039/D0AY01049A},
abstract = {Determination of elemental mass fractions in sediments plays a major role in evaluating the environmental status of aquatic ecosystems. Herewith, the optimization of a new total digestion protocol and the subsequent analysis of 48 elements in different sediment reference materials (NIST SRM 2702, GBW 07313, GBW 07311 and JMC-2) based on ICP-MS/MS detection is presented. The developed method applies microwave acid digestion and utilizes HBF4 as fluoride source for silicate decomposition. Similar to established protocols based on HF, HBF4 ensures the dissolution of the silicate matrix, as well as other refractory oxides. As HBF4 is not acutely toxic; no special precautions have to be made and digests can be directly measured via ICP-MS without specific sample inlet systems, evaporation steps or the addition of e.g. H3BO3, in order to mask excess HF. Different acid mixtures with and without HBF4 were evaluated in terms of digestion efficiency based on the trace metal recovery. The optimized protocol (5 mL HNO3, 2 mL HCL, 1 mL HBF4) allows a complete dissolution of the analyzed reference materials, as well as quantitative recoveries for a wide variety of certified analytes. Low recoveries for e.g. Sr, Ba and rare earth elements due to fluoride precipitation of HF-based digestions protocols, can be avoided by the usage of HBF4 instead. Based on the usage of high purity HBF4 all relevant trace, as well as matrix elements can be analyzed with sufficiently low LOQs (0.002 μg L−1 for U up to 6.7 μg L−1 for Al). In total, 34 elements were within a recovery range of 80%–120% for all three analyzed reference materials GBW 07313, GBW 07311 and JMC-2. 14 elements were outside a recovery range of 80%–120% for at least one of the analyzed reference materials.},
note = {Online available at: \url{https://dx.doi.org/10.1039/D0AY01049A} (DOI). Zimmermann, T.; von der Au, M.; Reese, A.; Klein, O.; Hildebrandt, L.; Pröfrock, D.: Substituting HF by HBF4 – an optimized digestion method for multi-elemental sediment analysis via ICP-MS/MS. In: Analytical Methods. Vol. 12 (2020) 30, 3778 - 3787. (DOI:  /10.1039/D0AY01049A)}}
@misc{klein_untersuchung_von_2019, 
author={Klein, O.},
title={Untersuchung von Borisotopenfraktionierung in verschiedenen Flusssystemen als potenzieller neuer Tracer fuer anthropogene Kontaminationsquellen (Masterarbeit)},
year={2019},
howpublished = {Master Thesis: Technische Hochschule Luebeck, FB Angewandte Naturwissenschaften},
note = {Klein, O.: Untersuchung von Borisotopenfraktionierung in verschiedenen Flusssystemen als potenzieller neuer Tracer fuer anthropogene Kontaminationsquellen (Masterarbeit). 2019.}}
@inproceedings{zimmermann_element_und_2019, 
author={Zimmermann, T. and Reese, A. and Retzmann, A. and Orth, T. and Klein, O. and Irrgeher, J. and Prohaska, T. and Proefrock, D.},
title={Element- und Isotopenanalytik in der marinen Umweltanalytik – Anwendungsgebiete und neue Entwicklungen zur Probenvorbereitung},
year={2019},
booktitle = {Vortrag im Rahmen eines Arbeitskreisseminars},
note = {Zimmermann, T.; Reese, A.; Retzmann, A.; Orth, T.; Klein, O.; Irrgeher, J.; Prohaska, T.; Proefrock, D.: Element- und Isotopenanalytik in der marinen Umweltanalytik – Anwendungsgebiete und neue Entwicklungen zur Probenvorbereitung. In: Vortrag im Rahmen eines Arbeitskreisseminars. Leoben (A), 13.03.2019, 2019.}}
@inproceedings{zimmermann_analysis_of_2019, 
author={Zimmermann, T. and Klein, O. and Orth, T. and Oppermann, B. and Retzmann, A. and Irrgeher, J. and Proefrock, D.},
title={Analysis of anthropogenic Gd emissions into the German North Sea and potential new insights by the analysis of Gd isotope ratios in MRI contrast agents},
year={2019},
booktitle = {European Winter Conference on Plasma Spectrochemistry 2019},
note = {Zimmermann, T.; Klein, O.; Orth, T.; Oppermann, B.; Retzmann, A.; Irrgeher, J.; Proefrock, D.: Analysis of anthropogenic Gd emissions into the German North Sea and potential new insights by the analysis of Gd isotope ratios in MRI contrast agents. In: European Winter Conference on Plasma Spectrochemistry 2019. Pau (F), 03.-08.02.2019, 2019.}}
@misc{klein_vergleichende_untersuchung_2017, 
author={Klein, O.},
title={Vergleichende Untersuchung von Multi-Elementfingerprints zweier Flusssysteme (Weser und Ems) unter besonderer
Beruecksichtigung der Metalle der Seltenen Erden (Bachelorarbeit)},
year={2017},
howpublished = {Bachelor Thesis: Fachhochschule Luebeck, FB Chemie- und Umwelttechnik},
note = {Klein, O.: Vergleichende Untersuchung von Multi-Elementfingerprints zweier Flusssysteme (Weser und Ems) unter besonderer
Beruecksichtigung der Metalle der Seltenen Erden (Bachelorarbeit). 2017.}}