Chemische Charakterisierung und Spurenanalytik
Filtern
Dokumenttyp
- Zeitschriftenartikel (41)
- Vortrag (24)
- Posterpräsentation (22)
- Sonstiges (4)
- Beitrag zu einem Tagungsband (2)
- Dissertation (1)
- Forschungsdatensatz (1)
Sprache
- Englisch (80)
- Deutsch (14)
- Mehrsprachig (1)
Schlagworte
- Immunoassay (9)
- ICP-MS (8)
- Amperometry (7)
- ELISA (6)
- Estrogens (5)
- LA-ICP-MS (5)
- LC-MS/MS (5)
- Laser ablation (5)
- Nanoparticle (5)
- Antikörper (4)
- Cell (4)
- Mass Spectrometry (4)
- Transformationsprodukte (4)
- Warfarin (4)
- Amoxicillin (3)
- BFR (3)
- Comparability (3)
- Cyclic voltammetry (3)
- Diclofenac (3)
- Effect based Method (3)
- GC-MS (3)
- MS based method (3)
- Mass spectrometry (3)
- Metabolomics (3)
- Metrology (3)
- Nontarget analysis (3)
- Ochratoxin A (3)
- Reliable measurements (3)
- Umweltsimulation (3)
- Wastewater (3)
- XRF (3)
- Abwasser (2)
- Accurate mass (2)
- Benz[a]anthracene (BaA) (2)
- Benzo[a]pyrene (BaP) (2)
- Biosensor (2)
- Cancer (2)
- Combustion Ion Chromatography (2)
- Compound annotation (2)
- E. coli (2)
- Electrochemistry (2)
- Electrospray ionization (2)
- Environmental simulation (2)
- Fertilizer (2)
- Finow Canal (2)
- Food analysis (2)
- Gas chromatography (GC) (2)
- Heart failure (2)
- Imaging (2)
- Isotope dilution (2)
- Isotope dilution (ID) (2)
- Legacy pollution (2)
- Liquid chromatography (LC) (2)
- Magnetic beads (2)
- Mass Spectroscopy (2)
- Mass spectrometry (MS) (2)
- Metformin (2)
- Method development (2)
- Methylmercury (2)
- Mobile phase (2)
- Multicellular spheroid (2)
- Nickel (2)
- PBFSM (2)
- PEG (2)
- Peptide analysis (2)
- Per- and Polyfluoroalkyl substances (PFAS) (2)
- Pollutants (2)
- Polycyclic aromatic hydrocarbon (PAH) (2)
- Polyethylene glycole (2)
- Polymer (2)
- Polypropylen (2)
- Polystyrol (2)
- Probenvorbereitung (2)
- Purity assessment (2)
- R package (2)
- RFA (2)
- Retrospective analysis (2)
- SARS-CoV-2 (2)
- Schadstoffaustrag (2)
- Schadstoffe (2)
- Sewage sludge (2)
- Umweltverhalten (2)
- Validation (2)
- WFD (2)
- Whole water samples (2)
- 6xHis (1)
- ACE2-Rezeptor (1)
- ATCUN (1)
- Adsorption (1)
- Affinity chromatography (1)
- Affinitätschromatographie (1)
- Aluminum oxide (1)
- Amino acid analysis (1)
- Analytical Sciences (1)
- Analytical methods (1)
- Antibiotics (1)
- Antibodies (1)
- Antibody (1)
- Antibody Quantification (1)
- Antibody quantification (1)
- Arzneimittel (1)
- Automation (1)
- BPA (1)
- Bacterial lysates (1)
- Bakterien (1)
- Basic solvent (1)
- Bead injection spectroscopy (1)
- Bewitterung (1)
- Biomarker (1)
- Biomarkers (1)
- Bioseparation (1)
- Bisphenol A (1)
- Bisphenol-A (1)
- Bisphenols (1)
- Bivalves (1)
- Blood-brain barrier (1)
- CCQM (1)
- CCQM key comparison (1)
- COVID-19 (1)
- Cardiolipins (1)
- Carrier (1)
- Chemical coverage (1)
- Chromatography (1)
- Chronic kidney disease (1)
- Climate Changes (1)
- Clinical samples (1)
- Cocaine (1)
- Copper (1)
- Corona (1)
- Corundum (1)
- Cyclization (1)
- Cylic Voltammetry (1)
- Cytoplasm (1)
- D-glucose (1)
- DCF (1)
- Data Analyses (1)
- Degradation (1)
- Diastolic dysfunction (1)
- Downstream processing (1)
- Dynamische Lichtstreuung (1)
- EDC (1)
- EDTAD (1)
- EPR spectroscopy (1)
- EQS (1)
- EU-WFD (1)
- Einzelzellanalyse (1)
- Electrochemical (1)
- Endocrine disruptor (1)
- Endokrine Disruptoren (1)
- Environment (1)
- Environmental analysis (1)
- Enzyme Immobilisation (1)
- Ergot alkaloids (1)
- Escherichia coli (1)
- Ethylenediaminetetraacetic acid (1)
- Expression (1)
- FTIR spectroscopy (1)
- Fatty acid metabolism (1)
- Fenton (1)
- Festphasenextraktion (1)
- Fingerprint (1)
- Flammschutzmittel (1)
- Flux Analysis (1)
- Folic acid (1)
- Fow injection analysis (1)
- Glucose (1)
- Größenausschlusschromatographie (1)
- HPLC (1)
- HPLC-MS (1)
- HPLC–MS (1)
- Halomonas elongata (1)
- Hapten Immunoassay (1)
- HexaHis-Tag (1)
- High pH (1)
- High-resolution mass spectrometry (1)
- His6 (1)
- His8 (1)
- Hormone (1)
- Human serum (1)
- Hydrolysis (1)
- Hydrolysis products (1)
- Hypothalamus (1)
- ICP-ToF-MS (1)
- ILC (1)
- IMAC purification (1)
- Immunocapture (1)
- Interlaboratory comparison (1)
- Interlaboratory key comparison (1)
- Iron disorders (1)
- Isotopologue Distribution (1)
- Kläranlage (1)
- Konjugate (1)
- L-alanine (1)
- LC-MS/MS peptide quantification (1)
- LFIA (1)
- Lab-on-chip (1)
- Lactate (1)
- Laser Ablation/Imaging (1)
- Lebensmittel (1)
- Linear dynamic range (1)
- Lipidomic profile (1)
- Lipidomics (1)
- Lipids (1)
- Liquid chromatography (1)
- Liquid chromatography-mass spectrometry (1)
- Liver X receptor (1)
- MALDI-TOF-MS (1)
- MALDI-ToF-MS (1)
- MOF (1)
- MST (1)
- Magnetic nanocatalyst (1)
- Magnetpartikel (1)
- Maillard reaction (1)
- Mass Isotopomer Distribution (1)
- Massenspektrometrie (1)
- Matrixeffekte (1)
- Melanoidin (1)
- Melanoidine (1)
- Mercury speciation (1)
- Meta-study (1)
- Metabolic Flux (1)
- Metabolic stress (1)
- Metabolites (1)
- Metalloprotein (1)
- Microdialysis (1)
- Microfluidic (1)
- Microparticles (1)
- Migration (1)
- Molecular imprinted polymers (1)
- Monoamine oxidase B (1)
- Mycotoxin (1)
- Mycotoxins (1)
- Mykotoxine (1)
- N-capsid (1)
- NMR spectroscopy (1)
- NSO-Heterozyklen (1)
- Nanobody (1)
- Nanoparticles (1)
- Nanopartikel (1)
- Naphthalene (Nap) (1)
- Nickel chelate (1)
- Non-target (1)
- Non-targeted analysis (1)
- Nontargeted approach (1)
- Nuclear receptor (1)
- Oberflächenwasser (1)
- Organic calibration solution (1)
- Organic contaminants (1)
- PEGomics (1)
- PFAS (1)
- PFAS TOP Assay soil contamination (1)
- PP (1)
- PS (1)
- Parkinsons's disease (1)
- Peptide (1)
- Peptide losses (1)
- Periplasma (1)
- Pharmaceutical Drugs (1)
- Pharmazeutika (1)
- Photocatalysis (1)
- Photodegradation (1)
- Photodynamische Inaktivierung (1)
- Photokatalyse (1)
- Photooxidation (1)
- Photosensibilisator (1)
- Phthalocyanin (1)
- Polishing (1)
- Pollution (1)
- Porphyrin (1)
- Prussian blue (1)
- Purity (1)
- QC (1)
- Quality control (1)
- RBD (1)
- Recombinant protein (1)
- Recovery (1)
- Reference material (1)
- Rekombinante Antikörper (1)
- Round robin exercise (1)
- Round robin test (1)
- SDS-PAGE (1)
- Sample treatment (1)
- Sapphire (1)
- Screen-printed electrodes (1)
- Sensing (1)
- Sewage treatment plant (1)
- Silanization (1)
- Silbernanopartikel (1)
- Smartphone (1)
- Software (1)
- Solid-phase extraction (1)
- Sonochemical synthesis (1)
- Speroid (1)
- Spheroid (1)
- Spike-Protein (1)
- Stability (1)
- Standardization (1)
- Surface water (1)
- TMB (1)
- Terbutryne (1)
- Therapeutic Drug Monitoring (1)
- Toxikologie (1)
- Transcriptomic (1)
- Transformation products (1)
- Transformations products (1)
- Triazine herbicide (1)
- Tumor metabolism (1)
- UV Bestrahlung (1)
- Validation trial (1)
- Validierung (1)
- Vhh (1)
- Vibrational Sum-Frequency Generation Spectroscopy (1)
- Virus (1)
- Wasser (1)
- Wasserproben (1)
- Water analysis (1)
- Weathering (1)
- Yerba mate tea (1)
- Zebrafisch (1)
- Zyklisierung (1)
- β-lactam (1)
Organisationseinheit der BAM
- 1.8 Umweltanalytik (95) (entfernen)
Paper des Monats
- ja (1)
Eingeladener Vortrag
- nein (24)
The CCQM-K148.a comparison was coordinated by the BIPM on behalf of the CCQM Organic Analysis Working Group for NMIs and DIs which provide measurement services in organic analysis under the CIPM MRA. It was undertaken as a "Track A" comparison within the OAWG strategic plan. CCQM-K148.a demonstrates capabilities for assigning the mass fraction content of a solid organic compound having moderate molecular complexity, where the compound has a molar mass in the range (75 - 500) g/mol and is non-polar (pKow < −2), when present as the primary organic component in a neat organic solid and where the mass fraction content of the primary component in the material is in excess of 950 mg/g.
Participants were required to report the mass fraction of Bisphenol A present in one supplied unit of the comparison material. Participants using a mass balance method for the assignment were also required to report their assignments of the impurity components present in the material. Methods used by the seventeen participating NMIs or DIs were predominantly based on either stand-alone mass balance (summation of impurities) or qNMR approaches, or the combination of data obtained using both methods. The results obtained using thermal methods based on freezing-point depression methods were also reported by a limited number of participants. There was excellent agreement between assignments obtained using all three approaches to assign the BPA content.
The assignment of the values for the mass fraction content of BPA consistent with the KCRV was achieved by most of the comparison participants with an associated relative standard uncertainty in the assigned value in the range (0.1 - 0.5)%.
The comparison required the assignment of the mass fraction of folic acid present as the main component in the comparison sample. Performance in the comparison is representative of a laboratory's measurement capability for the purity assignment of organic compounds of medium structural complexity [molecular weight range 300–500] and high polarity (pKOW < −2).
Methods used by the eighteen participating NMIs or DIs were based on a mass balance (summation of impurities) or qNMR approach, or the combination of data obtained using both methods. The qNMR results tended to give slightly lower values for the content of folic acid, albeit with larger associated uncertainties, compared with the results obtained by mass balance procedures. Possible reasons for this divergence are discussed in the report, without reaching a definitive conclusion as to their origin.
The comparison demonstrates that for a structurally complex polar organic compound containing a high water content and presenting a number of additional analytical challenges, the assignment of the mass fraction content property value of the main component can reasonably be achieved with an associated relative standard uncertainty in the assigned value of 0.5%
Immobilized metal affinity chromatography (IMAC) is a widely used technique for purifying polyhistidine-tagged recombinant proteins. However, it often has practical limitations that require complex optimizations and additional steps for purification. In this study, we introduce functionalized corundum particles as a novel, efficient, and economical method for purifying recombinant proteins in a column-free format. The corundum surface is modified with amino silane APTES, followed by EDTA dianhydride, and then loaded with nickel ions. We used the Kaiser test to monitor the modification process and ICP-MS to quantify the metal-binding capacity. To evaluate the system, we used His-tagged protein A/G (PAG) mixed with bovine serum albumin (BSA). The corundum particles exhibited a binding capacity of approximately 3 mg of protein per gram of corundum or 2.4 mg per 1 mL of corundum suspension. We also examined cytoplasm obtained from different E. coli strains as an example of a complex matrix. Varying the imidazole concentration in the loading and washing buffers showed that higher concentrations during loading improved purity. Even with sample volumes as large as one liter, we successfully isolated recombinant proteins down to a concentration of 1 µg/mL. We found higher purity levels with corundum when comparing the corundum material to standard Ni–NTA agarose beads. We successfully purified His6-MBP-mSA2, a fusion protein comprising monomeric streptavidin and maltose-binding protein, from E. coli cytoplasm, demonstrating the method's applicability. We also purified SARS-CoV-2-S-RBD-His8 expressed in human Expi293F cells, confirming its suitability for mammalian cell culture supernatants. The material cost of the nickel-loaded corundum material (without regeneration) is estimated to be less than 30 cents per gram of functionalized support or 10 cents per milligram of isolated protein. Another advantage of this system is the exceptional physical and chemical stability of corundum particles. Overall, we have demonstrated that this novel material offers an efficient, robust, and cost-effective purification platform for His-tagged proteins, even in challenging, complex matrices and large sample volumes with low product concentrations. This method has potential applications in both small laboratories and large-scale industrial settings.
Warfarin ist seit den 1950er Jahren einer der bekanntesten Gerinnungshemmer. Beim Menschen wird es bis heute zur Vorbeugung von Thrombose und der Behandlung von Vorhofflimmern und Arrhythmie eingesetzt. Doch schon einige Jahre vor der FDA Zulassung (U. S. Food and Drug Administration) als Medikament wurde es zur Bekämpfung von Nagetieren eingesetzt. Bis heute wurde es nur teilweise durch weitaus wirksamere antikoagulante Rodentizide (ARs) der zweiten Generation, sogenannte Superwarfarine, ersetzt.
In der Fachliteratur finden sich zahlreiche Beispiele für sekundäre und tertiäre Vergiftung mit ARs bei Wildtieren und anderen Nichtzieltieren. Bisher ist relativ wenig über die Bioakkumulation, Persistenz und Toxizität von ARs und deren Transformationsprodukten (TPs) in der terrestrischen und aquatischen Umwelt, sowie der Nahrungskette bekannt.
Um Einblicke in mögliche Transformations- und Abbauprozesse von Warfarin unter umweltrelevanten Bedingungen zu erhalten und um diese Einflüsse zu simulieren, wurde hierzu eine elektrochemische Reaktorzelle in Kopplung mit einem Massenspektrometer verwendet. So können mögliche Phase-I-Metabolite und sogenannte „oxidation products“ vorausgesagt werden. Hinsichtlich des Verhaltens während der Wasseraufbereitung in Kläranlagen wurden technisch relevante Prozesse wie Chlorung, UV-Bestrahlung und Ozonung in Modellen simuliert, um hier potenzielle Abbauwege und -prozesse aufzuklären. Gebildete Transformationsprodukte wurden daher mittels unterschiedlicher chromatografischer Verfahren getrennt und massenspektrometrisch identifiziert, charakterisiert und verglichen.
Warfarin ist seit den 1950er Jahren einer der bekanntesten Gerinnungshemmer. Beim Menschen wird es bis heute zur Vorbeugung von Thrombose und der Behandlung von Vorhofflimmern und Arrhythmie eingesetzt. Doch schon einige Jahre vor der FDA Zulassung (U. S. Food and Drug Administration) als Medikament wurde es zur Bekämpfung von Nagetieren eingesetzt. Bis heute wurde es nur teilweise durch weitaus wirksamere antikoagulante Rodentizide (ARs) der zweiten Generation, sogenannte Superwarfarine, ersetzt. In der Fachliteratur finden sich zahlreiche Beispiele für sekundäre und tertiäre Vergiftung mit ARs bei Wildtieren und anderen Nichtzieltieren. Bisher ist relativ wenig über die Bioakkumulation, Persistenz und Toxizität von ARs und deren Transformationsprodukten (TPs) in der terrestrischen und aquatischen Umwelt, sowie der Nahrungskette bekannt.
Um Einblicke in mögliche Transformations- und Abbauprozesse von Warfarin unter umweltrelevanten Bedingungen zu erhalten und um diese Einflüsse zu simulieren, wurde hierzu eine elektrochemische Reaktorzelle in Kopplung mit einem Massenspektrometer verwendet. So können mögliche Phase-I-Metabolite und sogenannte „oxidation products“ vorausgesagt werden. Hinsichtlich des Verhaltens während der Wasseraufbereitung in Kläranlagen wurden technisch relevante Prozesse wie Chlorung, UV-Bestrahlung und Ozonung in Modellen simuliert, um hier potenzielle Abbauwege und -prozesse aufzuklären. Gebildete Transformationsprodukte wurden daher mittels unterschiedlicher chromatografischer Verfahren getrennt und massenspektrometrisch identifiziert, charakterisiert und verglichen.
Solid wastewater-based fertilizers were screened for per- and polyfluoroalkyl substances (PFAS) by the extractable organic fluorine (EOF) sum parameter method. The EOF values for ten sewage sludges from Germany and Switzerland range from 154 to 7209 mg kg−1. For thermal treated sewage sludge and struvite the EOF were lower with values up to 121 mg kg−1. Moreover, the application of PFAS targeted
and suspect screening analysis of selected sewage sludge samples showed that only a small part of the EOF sum parameter values can be explained by the usually screened legacy PFAS. The hitherto unknown part of EOF sum parameter contains also fluorinated pesticides, pharmaceutical and aromatic compounds. Because these partly fluorinated compounds can degrade to (ultra-)short PFAS in wastewater treatment plants they should be considered as significant sources of organic fluorine in the environment. The combined results of sum parameter analysis and suspect screening reveal the need to update current regulations, such as the German fertilizer ordinance, to focus not solely on a few selected PFAS such as perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) but
consider an additional sum parameter approach as a more holistic alternative. Moreover, diffusion gradient in thin-films (DGT) passive samplers were utilized as an alternative simplified extraction method for PFAS in solid wastewater-based fertilizers and subsequently quantified via combustion ion chromatography. However, the DGT method was less sensitive and only comparable to the EOF values
of the fertilizers in samples with >150 mg kg−1, because of different diffusion properties for various PFAS, but also kinetic exchange limitations.
Per- and polyfluoroalkyl substances (PFAS) are chemicals which were developed to improve humanity’s quality of life. Due to their high chemical stability and resistance to degradation by heat or acids, PFAS were used in a variety of consumer products. The continuous use of PFAS in household products and the discharge of PFAS from industrial plants into the sewer system resulted in the contamination of effluents and sewage sludge from wastewater treatment plants (WWTPs) (Roesch et al. 2022). Since sewage sludge is often used as fertilizer, its application on agricultural soils has been observed as a significant entry path for PFAS into the environment, specifically in our food chain. In Germany the sewage sludge/biosolid application on agricultural land was banned with the amendment of the German Sewage Sludge Ordinance and by 2029 sewage sludge application will be totally prohibited. However, phosphorus (P) from sewage sludge should still be recycled in WWTPs of cities with a population larger than 50,000 residents. To produce high-quality P-fertilizers for a circular economy, PFAS and other pollutants (e.g. pesticides and pharmaceuticals) must be separated from sewage sludge. Due to the strong diversity of industrial PFAS usage it is not clear if a safe application of novel recycled P-fertilizers from WWTPs can be guaranteed. Therefore, we analyzed various sewage sludges and wastewater-based fertilizers. Sewage sludge (SL) samples from various WWTPs in Germany and Switzerland, six sewage sludge ashes (SSA) from Germany, six thermally treated SL and SSA samples with different additives (temperatures: 700-1050 °C), two pyrolyzed SL samples (temperature: 400 °C) and two struvite samples from Germany and Canada were analyzed. The goal was to quantify PFAS in sewage sludges and wastewater-based P-fertilizers with the sum parameter extractable organic fluorine (EOF) by combustion ion chromatography (CIC). The results were compared with data from classical LC-MS/MS target analysis as well as selected samples by HR-MS suspect screening. The EOF values of the SLs mainly range between 154 and 538 µg/kg except for one SL which showed an elevated EOF value of 7209 µg/kg due to high organofluorine contamination. For the SSA samples the EOF values were lower and values between LOQ (approx. 60 µg/kg) and 121 µg/kg could be detected. For the pyrolyzed SLs no EOF values above the LOQ were detected. Moreover, the two wastewater-based struvite fertilizers contain 96 and 112 µg/kg EOF, respectively. In contrast to the EOF values, the sum of PFAS target values were relatively low for all SLs. Additional applied PFAS HR-MS suspect screening aimed to tentatively identify PFAS that could contribute to the hitherto unknown part of the EOF value. The majority of the detected fluorinated compounds are legacy PFAS such as short- and long-chain perfluorocarboxylic acids (PFCA), perfluorosulfonic acids (PFSA), polyfluoroalkyl phosphate esters (PAPs) and perfluorophosphonic acids (PFPA). Moreover, fluorinated pesticides, pharmaceutical as well as aromatic compounds were also identified, which are all included in the EOF parameter. Our research revealed that the current PFAS limit of 100 µg/kg for the sum of PFOS + PFOA in the German Fertilizer Ordinance is no longer up to date. Since the number of known PFAS already exceeds 10,000, the ordinance limit should be updated accordingly. Recent regulations and restrictions on using long-chain PFAS (≥C8) have resulted in a significant shift in the industry towards (ultra-)short-chain alternatives, and other, partly unknown, emerging PFAS. Ultimately, also fluorinated pesticides and pharmaceuticals, which end up as ultrashort PFAS in the WWTPs, have to be considered as possible pollutants in fertilizers from wastewater, too.
Mykotoxine sind sekundäre Stoffwechselprodukte, die von Schimmelpilzen gebildet werden. Sie sind unvermeidliche Lebensmittelkontaminanten und stellen daher ein ernstes Gesundheitsrisiko für Mensch und Tier dar. Aus diesem Grund hat die Europäische Kommission Vorschriften erlassen, die Höchstwerte für Mykotoxine in bestimmten Lebensmitteln vorsehen. Um die gesetzlichen Grenzwerte einzuhalten, müssen in der Lebensmittelindustrie Mykotoxinanalysen der eingehenden Waren durchgeführt werden.
Gegenwärtig umfasst die Analyse zeitaufwändige Probenvorbereitungsschritte, denen in der Regel eine chromatographische Analyse folgt.
Immunoassays ermöglichen eine Vor-Ort-Analyse, aber in der Regel sind für feste Lebensmittelproben lösungsmittelbasierte Extraktionsschritte erforderlich. Da Immunoassays in der Regel nicht mit den hohen Lösungsmittelkonzentrationen kompatibel sind, die üblicherweise für die Mykotoxinextraktion verwendet werden (z.B. Acetonitril oder Methanol), war es das Ziel dieser Arbeit, ein Extraktionsverfahren für die Mykotoxine Deoxynivalenol und Ochratoxin A aus Weizenmehl und Getreide zu entwickeln, das für Immunoassays und -sensoren verwendet werden kann. Vier verschiedene Lösungsmittel, Methanol (10 %), Ethanol (5 %) und Acetonitril (10 %) sowie Milli-Q-Wasser wurden für die Extraktion des Analyten Deoxynivalenol getestet. Um negative Umweltaspekte zu vermeiden und aufgrund der vergleichbaren Extraktionseffizienz von Milli-Q-Wasser gegenüber den anderen Lösungsmitteln, wurde Milli-Q-Wasser als Extraktionslösung im optimierten Extraktionsprotokoll für Deoxynivalenol verwendet.
Es wurden verschiedene Extraktionsbedingungen, wie die Extraktionszeit, das Lösungsmittel-Feststoff-Verhältnis, der Filtrationsschritt, der Zentrifugationsschritt sowie die Zusammensetzung des Wassers untersucht. Auf der Grundlage der Ergebnisse wurde ein Extraktionsprotokoll festgelegt, mit dem Wiederfindungsraten in einem Bereich von x bis x erzielt wurden. Das Extraktionsprotokoll umfasste die Extraktion von 2 g Weizenmehl mit 40 ml Milli-Q-Wasser für 30 Minuten, die anschließende Zentrifugation bei 3000 U/min für 15 Minuten bei 4 °C und die Filtration des Überstands.
Metformin is widely used as a first-line treatment for type 2 diabetes, but central effects of metformin have received little attention. When metformin (200 mg/kg i.p.) was administered to C57Bl6 mice, metformin concentration in cerebrospinal fluid peaked at 29 μM after 30 min but dropped quickly and was low at 90 min. In mouse hypothalamus sampled by microdialysis, systemically administered metformin caused minor and transient increases of acetylcholine, glucose and lactate while choline levels decreased. When metformin (0.2−10 mM) was locally infused via retrodialysis, there was a short-lasting increase of acetylcholine in the hypothalamus. Extracellular lactate levels in hypothalamus showed a massive increase upon metformin infusion while glucose levels decreased. In isolated mitochondria of mouse brain, metformin inhibited oxygen consumption and the activity of complex I. Inhibition of mitochondrial respiration likely explains lactate formation in the brain during metformin infusion which may cause lactic acidosis during metformin intoxication. The changes of cholinergic activity in the hypothalamus may be associated with appetite suppression observed during metformin treatment.
Estrogens are endocrine disrupting chemicals and of high concerns due to demonstrated harmful effects on the environment and low effect levels. For monitoring and risk assessment, several estrogens were included in the "watch list" of the EU Water Framework Directive which sets very low environmental quality standard (EQS) levels for Estrone (E1) and 17β-Estradiol (E2) of 0.4 ng L−1 and for 17α-Ethinylestradiol (EE2) of 0.035 ng L−1 requiring sensitive detection methods, as well as extensive sample preparation. A sensitive, derivatization-free, isotope dilution calibration HPLC-MS/MS method for a panel of 5 selected estrogens (including the 3 estrogens of the EU WFD watchlist), and a procedure for the reproducible preparation of a representative whole water matrix including mineral water, humic acids and solid particulate matter are presented. These are used in a diligent comparison of classical solid phase extraction (SPE) on hydrophilic-lipophilic balanced (HLB) phase to SPE on an estrogen-specific molecularly imprinted polymer phase (MISPE) for ultra-trace levels of the analytes (1–10 ng L−1). Additionally, a two-step procedure combining HLB SPE disks followed by MISPE is evaluated. The tow-step procedure provides superior enrichment, matrix removal and sample throughput while maintaining comparable recovery rates to simple cartridge SPE. Estimated method quantification limits (MQLs) range from 0.109–0.184 ng L−1 and thus meet EQS-levels for E1 and E2, but not EE2. The representative whole water matrix provides a reproducible comparison of sample preparation methods and lays the foundation for a certified reference material for estrogen analysis. The presented method will serve as the basis for an extended validation study to assess its use for estrogen monitoring in the environment.