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Organisationseinheit der BAM
HBCD stereoisomer pattern in mirror carps following dietary exposure to pure Gamma-HBCD enantiomers
(2010)
Der Einsatz aktiver (Pumpprobennahme,
Schöpfprobennahme) und passiver (Diffusionsprobennahme)
Probennahmetechniken zur Gehaltsbestimmung von
LHKW sowie Ethen und Methan in Grundwasser wird aus
ordnungsbehördlicher Sicht hinsichtlich der Vergleichbarkeit
von Analysendaten untersucht. Am Beispiel einer Kontamination
mit Trichlorethen sowie 1,2-Dichlorethen und
Vinylchlorid kann deutlich gemacht werden, dass die Einsatzmöglichkeit
der passiven Probennahme durch unzureichende
Strömungsverhältnisse im Aquifer sowie biologische
Aktivität im Pegelrohr begrenzt ist. Der aktiven Probennahme
ist bei ungeklärten oder unzureichenden Strömungsverhältnissen
im Grundwasserleiter daher der Vorzug
zu geben. Das gaschromatographische Verfahren für Vinylchlorid
mittels Dampfraumtechnik wird um die Quantifizierung
von Methan und Ethen erweitert. Dabei werden für
die Bewertung von Altlasten relevante Bestimmungsgrenzen
von 0,1 µg/l (Vinylchlorid, Ethen) sowie 5 µg/l (Methan)
erreicht.
Aus der Validierung der Analysenmethode und den
Ergebnissen verschiedener Probennahmen werden Toleranzbereiche
für die Ergebnisse eines Grundwassermonitorings
abgeschätzt. Diese Streubreiten von Monitoring-
Ergebnissen sollten von Ingenieurbüros und zuständigen
Ordnungsbehörden bei der Bewertung der komplexen Abbauprozesse
eines LHKW-Grundwasserschadens beachtet
werden.
A number of currently recommended sampling techniques for the determination of hydrogen in contaminated groundwater were compared regarding the practical proficiency in field campaigns. Key characteristics of appropriate sampling procedures are reproducibility of results, robustness against varying field conditions such as hydrostatic pressure, aquifer flow, and biological activity. Laboratory set-ups were used to investigate the most promising techniques. Bubble stripping with gas sampling bulbs yielded reproducible recovery of hydrogen and methane which could be verified for groundwater sampled in two field campaigns. The methane content of the groundwater was confirmed by analysis of directly pumped samples thus supporting the trueness of the stripping results. Laboratory set-ups and field campaigns revealed that bubble stripping of hydrogen may be restricted to the type of used pump. Concentrations of dissolved hydrogen after bubble stripping with an electrically driven submersible pump were about one order of magnitude higher than those obtained from diffusion sampling. The gas chromatographic determination for hydrogen and methane requires manual injection of gas samples and detection by a pulsed discharge detector (PDD) and allows limits of quantification of 3 nM dissolved hydrogen and 1 µg L-1 dissolved methane in groundwater. The combined standard uncertainty of the bubble stripping and GC/PDD quantification of hydrogen in field samples was 7% at 7.8 nM and 18% for 78 nM.
High-performance liquid chromatography tandem mass spectrometry (HPLC–MS/MS) was applied to sterospecifically quantify the content of α-, β-, and γ-hexabromocyclododecane (HBCD) in six fish species from the Norwegian Etnefjorden. A combination of a β-PM cyclodextrin and an achiral column enabled the paired chromatographic separation of the stereoisomers in the order (-)-α-, (+)-α-, (-)-β-, (+)-β-, (+)-γ- and, (-)-γ-HBCD. The limits of detection were in the range of 6–21 pg g-1 depending on the stereoisomer and the concentrations of α-, β-, and γ-HBCD in fillets ranged from <5.4 ng g-1 to 11.1 µg g-1 lipid weight. α-HBCD enantiomers were throughout dominating, and in most cases the accumulation of the respective first eluted enantiomers ((-)-α-, (-)-β- and (+)-γ-HBCD) was observed. Deviations from the racemic EF-value were considered to be significant if it was outside of the expanded uncertainty range for each of the racemic HBCD-ratios. The composition of HBCD isomers varied between the investigated fish species and the relative high values for the γ-HBCD concentrations for the bottom-dwellers flounder and thorny skate seems to echo the HBCD pattern of ocean sediments.
Hexabromocyclododecane enantiomers: microsomal degradation and patterns of hydroxylated metabolites
(2011)
The degradation of the enantiomers of α-, β-, and γ-hexabromocyclododecane (HBCD) by phase I metabolism was investigated using induced rat liver microsomes. HBCD isomers were quantified using HPLC-MS/MS (ESI-) after separation on a combination of a reversed phase and a chiral analytical column. The degradation of all six isomers followed first-order kinetics and the estimated half-lives ranged from 6.3 min for both β-HBCD enantiomers to 32.3 min in case of (+)-γ-HBCD. (+)-α- and (–)-γ-HBCD displayed significantly shorter half-lives than their corresponding antipodes. It could be shown that this degradation led to a significant enrichment of the first eluting enantiomers (–)-α- and (+)-γ-HBCD. Individual patterns of mono- and dihydroxylated derivatives obtained from each α- and γ-HBCD enantiomer were seen to be distinctly characteristic. The patterns of monohydroxylated HBCD derivatives detected in liver and muscle tissues of pollack, mackerel and in herring gull eggs were largely similar to those observed in the in vitro experiments with rat liver microsomes. This enabled individual hydroxy-HBCDs to be assigned to their respective parent HBCD enantiomers.
Levels of α-, β-, and γ-hexabromocyclododecane (HBCD) were determined in pooled eggs from herring gulls (Larus argentatus) sampled on three bird sanctuaries near the German North Sea coast between 1988 and 2008 (Mellum and Trischen) and the German Baltic Sea coast between 1998 and 2008 (Heuwiese) and archived by the German Environmental Specimen Bank. Pressurized fluid extraction, gel permeation chromatography, and LCMS/MS using 13C12-labelled isotope standards and a chiral column were applied. α-HBCD was the dominating diastereomer and ranged between 3.7 and 107 ng g-1 lw while β- and γ-HBCD were throughout close to LOQ. The highest α-HBCD concentration was found in eggs from Mellum sampled in the year 2000. Interestingly, HBCD in eggs from the three islands displayed similar time courses with levels increasing to a peak contamination around 2000 and decreasing levels ever since. Chiral signatures of α-HBCD in eggs differed among the islands but indicated a preferential enrichment of the first eluting enantiomer (-)-α-HBCD.
The reliability in measurement results obtained during environmental monitoring is crucial for the assessment and further planning of remediation efforts on the respective contaminated sites by the responsible authorities. A case study concerned with groundwater contaminated with perchloroethylene, trichloroethylene and 1,1,2-trichlorotrifluoroethane including their degradation products which involves private contract laboratories and an independent provider of quality assurance (QA) is presented. The experience gained with biannual monitoring campaigns over 14 years indicates that the selection of contractors on basis of accreditation status and successful performance in interlaboratory comparisons are not sufficient. Rather the auditing of the contractors by the QA provider prior to each campaign and the crosschecking of selected monitoring samples by the QA provider led to a lasting improvement of reliability in the contractors' measurement results. A mean deviation of 20% from the reference value determined by the QA provider for the crosschecked samples was reached.
Aim: The objective of the study was to provide conclusive evidence for the effect of particle size reduction as by milling on the extractable content of ethyl glucuronide (EtG) of hair samples. Methods: A number of real case hair samples and two pooled hair materials with EtG contents in the range of 1030 pg/mg were systematically compared with regard to the extraction yield of EtG after cutting to 23 mm length and pulverization with a ball mill. After the respective treatment the samples were submitted to aqueous extraction followed by quantification of EtG using HPLC-MS/MS. Results: It was unequivocally demonstrated that milling of hair samples prior to aqueous extraction significantly increases the extractable EtG content compared with cut hair. The effect ranged between 137 and 230% and was seen to occur regardless of the extent of pulverization. Cooling of samples was not necessary to prevent partial degradation of EtG during the grinding procedure. Conclusion: The options currently employed at choice in analytical practice (cutting or milling) were seen to significantly affect the extractable amount of EtG in hair. This is suspected to influence the degree of equivalence of quantification results obtained in different laboratories as well as their respective classification of a test subject's drinking behaviour on the basis of currently recommended cut-off values.