Effect of TiO2 nanoparticles and UV radiation on extracellular enzyme activity of intact heterotrophic biofilms.

When introduced into the aquatic environment, TiO2 NP are likely to settle from the water column, which results in increased exposure of benthic communities. Here, we show that the activity of two extracellular enzymes of intact heterotrophic biofilms, ß-glucosidase (carbon-cycling) and l-leucin aminopeptidase (nitrogen-cycling), was reduced following exposure to surface functionalized TiO2 NP and UV radiation, depending on the particles' coating. This reduction was partially linked to ROS production. Alkaline phosphatase (phosphorus-cycling) activity was not affected, however in contrast, an alkaline phosphatase isolated from E. coli was strongly inhibited at lower concentrations of TiO2 NP than the intact biofilms. These results indicate that enzymes present in the biofilm matrix are partly protected against exposure to TiO2 NP and UV radiation. Impairment of extracellular enzymes which mediate the uptake of nutrients from water may affect ecosystem function.

Endocrine disrupting compounds affecting corticosteroid signaling pathways in Czech and Swiss waters: potential impact on fish.

This study investigated the occurrence of corticosteroid signaling disruptors in wastewaters and rivers in the Czech Republic and in Switzerland. 36 target compounds were detected using HPLC-MS/MS, with up to 6.4 µg/L for azole antifungals that indirectly affect corticosteroid signaling. Glucocorticoid receptor (GR)-mediated activity was determined using the GR-CALUX bioassay with dexamethasone equivalent concentrations ranging from

LC-MS/MS determination of potential endocrine disruptors of cortico signalling in rivers and wastewaters.

A targeted analytical method was established to determine a large number of chemicals known to interfere with the gluco- and mineralocorticoid signalling pathway. The analytes comprise 30 glucocorticoids and 9 mineralocorticoids. Ten out of these corticosteroids were primary metabolites. Additionally, 14 nonsteroids were included. These analytes represent a broader range of possible adverse modes of action than previously reported. For the simultaneous determination of these structurally diverse compounds, a single-step multimode solid-phase extraction and pre-concentration was applied. Extracts were separated by a short linear HPLC gradient (20 min) on a core shell RP column (2.7 µm particle size) and compounds identified and quantified by LC-MS/MS. The method provided excellent retention time reproducibility and detection limits in the low nanograms per litre range. Untreated hospital wastewater, wastewater treatment plant influent, treated effluent and river waters were analysed to demonstrate the applicability of the method. The results show that not all compounds were sufficiently eliminated by the wastewater treatment, resulting in the presence of several steroids (∼20 ng/L) and nonsteroids in the final effluent, some of them at high concentrations up to 200 ng/L. Most of the detected mono-hydroxylated steroidal transformation products were found at significantly higher concentrations than their parent compounds. We therefore recommend to include these potentially bioactive metabolites in environmental toxicity assessment.

Inductively coupled plasma mass spectrometry (ICP MS): a versatile tool.

Inductively coupled plasma (ICP) mass spectrometry (MS) is routinely used in many diverse research fields such as earth, environmental, life and forensic sciences and in food, material, chemical, semiconductor and nuclear industries. The high ion density and the high temperature in a plasma provide an ideal atomizer and element ionizer for all types of samples and matrices introduced by a variety of specialized devices. Outstanding properties such as high sensitivity (ppt-ppq), relative salt tolerance, compound-independent element response and highest quantitation accuracy lead to the unchallenged performance of ICP MS in efficiently detecting, identifying and reliably quantifying trace elements. The increasing availability of relevant reference compounds and high separation selectivity extend the molecular identification capability of ICP MS hyphenated to species-specific separation techniques. While molecular ion source MS is specialized in determining the structure of unknown molecules, ICP MS is an efficient and highly sensitive tool for target-element orientated discoveries of relevant and unknown compounds. This special-feature, tutorial article presents the principle and advantages of ICP MS, highlighting these using examples from recently published investigations.

Multimode gradient high performance liquid chromatography mass spectrometry method applicable to metabolomics and environmental monitoring.

Metabolomics or environmental investigations generate samples containing very large numbers of small molecular weight analytes. A single mode chromatographic separation excludes a substantial part of such complex analyte mixtures. For instance, a reversed-phase separation would not retain ionic species, resulting in a correspondingly huge front peak. To address this problem, we used two commercially available mixed-mode ion-exchange reversed-phase columns (WAX-1 and WCX-1) in sequence in a novel multimode separation method. After trapping hydrophobics on a C18-trap in loop position, hydrophilics passing the trap are separated by a simultaneous gradient for HILIC, anion and cation exchange chromatography. This gradient ends in a washout phase with a high percentage of water, the correct starting conditions for a reversed-phase gradient eluting hydrophobics from the trap in a second step of the run. Amino acids (9), organic acids (2), sugars (8), fatty acid derived compounds (11), antioxidants (4), miscellanea (6) and xenobiotics (4) were analyzed. Compounds were separated after a single sample injection during a 50min run. Lipids derived small fatty acids up to a chain length of 12 carbons were also accessible within this run time.

Determination of strong binding chelators and their metal complexes by anion-exchange chromatography and inductively coupled plasma mass spectrometry.

Based on the negative charge of polycarboxylic chelators, an anion-exchange separation has been developed that is compatible with sensitive metal detection by ICP-MS. A low capacity hydrophilic polymer (AS11) was used as the anion exchanger and ammonium nitrate as the eluent. The new procedure provided high selectivity in the isocratic mode as well as a large separation window and high separation efficiency in the gradient mode. This was demonstrated for different types of chelators and their metal complexes. The aminopolycarboxylates NTA, EDTA, CDTA, DTPA, EDDS and for the EDTA derivatives HEDTA, ED3A and EDTMP, the phosphonic acid analogue of EDTA were tested. Their retention times generally depended on the charge, which was lower in 1:1 metal chelator complexes. Evaluation of the separation mechanism demonstrated that they were all separated predominantly by an anion-exchange mechanism with only a minor contribution from hydrophobic attraction. The method is useful for species identification and for predicting the charge of unknown analogous species from retention times. A gradient separation procedure achieved on-column preconcentration and matrix removal for the interference-free detection of metal chelates down to low nanomolar concentration in samples from various fields of environmental research.

Ground water pollution by roof runoff infiltration evidenced with multi-tracer experiments.

The infiltration of urban roof runoff into well permeable subsurface material may have adverse effects on the ground water quality and endanger drinking water resources. Precipitation water from three different roofs of an industrial complex was channelled to a pit and infiltrated into a perialpine glaciofluvial gravel-and-sand aquifer. A shaft was constructed at the bottom of the pit and equipped with an array of TDR probes, lysimeters and suction cups that allowed measuring and sampling soil water at different depths. A fast infiltration flow was observed during natural rainfall events and during artificial infiltration experiments. For a better understanding of the behaviour of contaminants, experiments were conducted with cocktails of compounds of different reactivity (ammonium, strontium, atratone) and of non-reactive tracers (uranine, bromide, naphthionate), which represent different classes of pollutants. The experiment identified cation exchange reactions influencing the composition of the infiltrating water. These processes occurred under preferential flow conditions in macropores of the material. Measuring concentration changes under the controlled inflow of tracer experiments, the pollution potential was found to be high. Non-reactive tracers exhibited fast breakthrough and little sorption.

Quantification of methylated selenium, sulfur, and arsenic in the environment.

Biomethylation and volatilization of trace elements may contribute to their redistribution in the environment. However, quantification of volatile, methylated species in the environment is complicated by a lack of straightforward and field-deployable air sampling methods that preserve element speciation. This paper presents a robust and versatile gas trapping method for the simultaneous preconcentration of volatile selenium (Se), sulfur (S), and arsenic (As) species. Using HPLC-HR-ICP-MS and ESI-MS/MS analyses, we demonstrate that volatile Se and S species efficiently transform into specific non-volatile compounds during trapping, which enables the deduction of the original gaseous speciation. With minor adaptations, the presented HPLC-HR-ICP-MS method also allows for the quantification of 13 non-volatile methylated species and oxyanions of Se, S, and As in natural waters. Application of these methods in a peatland indicated that, at the selected sites, fluxes varied between 190-210 ng Se·m(-2)·d(-1), 90-270 ng As·m(-2)·d(-1), and 4-14 µg S·m(-2)·d(-1), and contained at least 70% methylated Se and S species. In the surface water, methylated species were particularly abundant for As (>50% of total As). Our results indicate that methylation plays a significant role in the biogeochemical cycles of these elements.

Arsenic speciation by gradient anion exchange narrow bore ion chromatography and high resolution inductively coupled plasma mass spectrometry detection.

Based on gradient anion exchange chromatography (AEC), a new strategy in As-speciation was evaluated. A narrow bore chromatographic system with lower flow rates (

Effect of cadmium on the interaction of 17beta-estradiol with the rainbow trout estrogen receptor.

The widely reported negative effects of xenoestrogens on the endocrine system of aquatic organisms gave raise to public concern and led to a number of screening and testing initiatives on the international level. Recent studies indicated that not only organic chemicals but also certain heavy metals, including cadmium, can mimic the effects of the endogenous estrogen receptor agonist 17beta-estradiol (E2) and lead to estrogen receptor activation. While the effects of cadmium on the endocrine system and its potential to harm living organisms are no longer in doubt, the exact mode of action is still essentially unknown. In the present study we utilized the rainbow trout ER alpha ligand binding domain (rtER-LBD) fused to glutathione-S-transferase, to study noncovalent interactions between cadmium and the rtER-LBD. ICP-MS data showed that the Cd uptake by the rtER-LBD was strongly pH-dependent. Previous results showing that Cd shields Cys residues of the rtER-LBD against chemical modification, and competitive binding experiments reported here provide insights into the specificity of the interaction of cadmium with the ER hormone binding cavity. It could, for instance, be shown that most of the cadmium adsorbed to the protein could be released into solution either under denaturing conditions, or by stripping from the protein surface using EDTA at physiological conditions. Competitive binding experiments using radio-labeled estradiol showed that, in contrast to previously published data, E2 has an affinity an order of magnitude higher for the ER than for Cd. ICP-MS experiments showed that, despite its higher affinity, increasing E2 concentrations were unable to replace Cd from the rtER-LBD that had been preequilibrated with Cd. These findings were independently confirmed by the [3H]-E2 binding assay. At the same time both ICP-MS and the [3H]-E2 binding assay showed that increasing Cd concentrations not only lead to a decrease in the specific estradiol binding, but also to the release of E2 from the preequilibrated rtER-LBD. The gradual release of [3H]-E2 from the rtER-LBD following incubation with increasing Cd concentrations indicates either direct competition for the same binding site or Cd-induced conformational changes resulting in the release of estradiol.

Speciation of heavy metals in environmental water by ion chromatography coupled to ICP-MS.

Biogenic (e.g. phytochelatins, porphyrins, DOM) as well as anthropogenic (e.g. NTA, EDTA, phosphonates) chelators affect the mobility and cycling of heavy metals in environmental waters. Since such chelators can form strongly bound anionic heavy metal complexes that are stable and highly mobile, anion-exchange chromatography coupled to ICP-MS was investigated. A narrow bore HPLC system was connected to a micro concentric nebuliser for in-line sample introduction. A new chromatographic procedure based on a synthetic hydrophilic quaternary ammonium anion exchanger in combination with nitrate as a strong eluent anion, and gradient elution, provided high separation selectivity and a large analytical window. Low detection limits (nmol L(-1)) were achieved by on-column matrix removal and sample preconcentration. This allowed the method to be successfully applied to different environmental research areas. In ecotoxicological studies of heavy metal effects on algae low concentrations of metal EDTA complexes were determined in nutrient solutions without interference from high (buffer) salt concentrations. In groundwater, infiltrated by a polluted river, mobile metal EDTA species were observed. In river water of different pollution levels beside CuEDTA other anionic Cu-complexes were found in nmol L(-1) concentrations.