Biomedical subjects

G Schüürmann

Publications and source records attributed to G Schüürmann.

At least 19 recordsLinked to original sources

PubMed2004

Dialysis of persistent organic pollutants and polycyclic aromatic hydrocarbons from semipermeable membranes. A procedure using an accelerated solvent extraction device.

Accelerated solvent extraction (ASE) is one of the most recent solid-phase extraction methods and has caught on all over the world in numerous laboratories. Until now it was not known that this device is also very suitable for performing dialysis. In this study, development of a rapid dialysis procedure (RDP) was described that is based on the dialysis of persistent organic xenobiotics from triolein-containing semipermeable membrane devices (SPMDs) using ASE. All the operating parameters were optimized within the framework of usage. The RDP procedure was compared with the conventional dialytic recovery of target analytes under atmospheric pressure using spiked analytes and real field samples of SPMDs exposed to urban air. The main advantages of the RDP in comparison to the conventional dialysis are the speed, with up to 70 times faster taking only 40 min, and the considerable reduction in solvent consumption (by two-thirds) when SPMDs with standard configuration are used. Moreover, the RDP is also suitable as an analytical cleanup procedure for the same analytes from various types of lipid samples and other difficult matrixes using semipermeable membranes.

Journal Article↗

PubMed2003

One-step cleanup for PAH residue analysis in plant matrices using size-exclusion chromatography.

A new one-step cleanup procedure, based on size-exclusion chromatography (SEC), usable for the extracts from accelerated solvent extraction (ASE), Soxhlet extraction, or ultrasonic extraction (USE), is described. The method is suitable for the determination of polycyclic aromatic hydrocarbons (PAHs), especially from very complicated plant matrices (e.g. pine needles, deciduous leaves, mosses). The main improvement compared with previous conventional procedures is that analyte peaks barely overlap with matrix peaks in the chromatograms and that it is a very rapid and simple one-step procedure with clearly improved analytical performance. Essential advantages of this SEC procedure are the sharper GC-MS chromatograms for the PAH fraction at retention times between 9.2 and 12.0 min, distinctly separated substance peaks resulting in better analysis, shorter running times, and lower solvent consumption.

Acer↗

PubMed2002

Fate of POPs (DDX, HCHs, PCBs) in upper soil layers of pine forests.

Organochlorines (HCH isomers, DDX and individual PCBs) were determined in pine needle litter and upper soil layers of three forest test areas in central Germany. The contents accumulating over a number of years or even decades in the organic surface layer are compared with the levels of new inputs from needle fall as well as with the levels of older inputs in the upper mineral soil layer. Differences in behaviour between the soil horizons are discussed, especially concerning the DDX and HCH groups. With approximately comparable Corg values (approx. 21-24%) the pH value in the range of 4.24-2.90 in the O-horizon of the forest soils exerts a large influence. Hence the A-horizon represents--for p,p'-DDT and gamma-HCH in particular--at pH values of 2.90 a pollutant reservoir which should not be underestimated and which could endanger the rhizosphere and the groundwater. According to PCBs, in the more acidic soils with a pH value <4.0 the lipophilic higher polychlorinated biphenyls were found to be more highly enriched in the humus layer.

Dichlorodiphenyl Dichloroethylene↗

PubMed2001

Membrane-enclosed sorptive coating. an integrative passive sampler for monitoring organic contaminants in water.

An integrative sampler that consists of a bar coated with poly(dimethylsiloxane) (PDMS) enclosed in a dialysis membrane bag has been developed combining the advantages of the passive sampling approach with solventless preconcentration of organic solutes from aqueous matrixes and subsequent desorption of the sequestered analytes on-line with a capillary GC/MS system. The performance of the sampler was tested for integrative sampling of hydrophobic persistent organic pollutants including gamma-hexachlorocyclohexane, hexachlorobenzene, 2,2'-bis(4-chlorophenyl)-1,1'-dichloroethylene, polycyclic aromatic hydrocarbons, and polychlorinated biphenyls in the laboratory in a continuous-flow system. Linear uptake of all test analytes during exposure periods up to one week has been observed, and concentration proportionality of response of the sampler has been demonstrated. Over the range of controlled laboratory conditions, the magnitude of sampling rate values varied from 47 to 700 microL h(-1) per sampler. The uptake rate of chemicals was dependent on their molecular mass, as well as on the partition coefficient between the PDMS and water. A decrease in sampling rates with decreasing water temperature was observed. The sampling device has the potential to detect low aqueous concentrations (ng to pg L(-1)) of test substances.

Adsorption↗

PubMed2001

Persistent organic pollutants in agricultural soils of central Germany.

Concentrations of persistent organic pollutants (HCHs, DDX, PCBs and HCB) were measured in topsoils from 11 agricultural fields in the lee of large disused industrial plants in the Leipzig-Halle region at varying distances from emitters. The investigations clearly indicate the deposition of anthropogenic pollutant inputs, not only in the past, but also today. The pollution potential was assessed on the basis of current guide values and limits, as well as in relation to values found in agricultural soils elsewhere in Germany, in Europe and in the USA. The reference values were mainly exceeded for DDX and gamma-HCH (lindane). The PCB pattern was determined and the degradation ratios between the parent substances and their metabolites (DDX and HCH isomers) were calculated in order to distinguish between the previous and current pollutant input of pesticides by means of principal component analysis.

Agriculture↗

PubMed2001

Use of semipermeable membrane devices (SPMDs). Determination of bioavailable, organic, waterborne contaminants in the industrial region of Bitterfeld, Saxony-Anhalt, Germany.

Triolein-containing semipermeable membrane devices (SPMDs) were employed as passive samplers to provide data on the bioavailable fraction of organic, waterborne, organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polynuclear aromatic hydrocarbons (PAHs) in streams flowing through a highly polluted industrial area of Bitterfeld in Saxony-Anhalt, Germany. The contamination of the region with organic pollutants originates in wastewater effluents from the chemical industry, from over one-hundred years of lignite exploitation, and from chemical waste dumps. The main objective was to characterise time-integrated levels of dissolved contaminants, to use them for identification of spatial trends of contamination, and their relationship to potential pollution sources. SPMDs were deployed for 43 days in the summer of 1998 at four sampling sites. The total concentration of pollutants at sampling sites was found to range from a low of 0.8 microgram/SPMD to 25 micrograms/SPMD for PAHs, and from 0.4 microgram/SPMD to 22 micrograms/SPMD for OCPs, respectively. None of the selected PCB congeners was present at quantifiable levels at any sampling site. A point source of water pollution with OCPs and PAHs was identified in the river system considering the total contaminant concentrations and the distribution of individual compounds accumulated by SPMDs at different sampling sites. SPMD-data was also used to estimate average ambient water concentrations of the contaminants at each field site and compared with concentrations measured in bulk water extracts. The truly dissolved or bioavailable portion of contaminants at different sampling sites ranged from 4% to 86% for the PAHs, and from 8% to 18% for the OCPs included in the estimation. The fraction of individual compounds found in the freely dissolved form can be attributed to the range of their hydrophobicity. In comparison with liquid/liquid extraction of water samples, the SPMD method is more suitable for an assessment of the background concentrations of hydrophobic organic contaminants because of substantially lower method quantification limits. Moreover, contaminant residues sequestered by the SPMDs represent an estimation of the dissolved or readily bioavailable concentration of hydrophobic contaminants in water, which is not provided by most analytical approaches.

Environmental Monitoring↗

PubMed2001

Application of different RP-HPLC methods for the determination of the octanol/water partition coefficient of selected tetrachlorobenzyltoluenes.

Reversed-phase high-performance liquid chromatography (RP-HPLC) in both, isocratic and gradient elution mode (stationary phase: LiChrospher 100 RP-18; mobile phase: water/methanol or water/acetonitrile) was used for a renewed determination of octanol/water partition coefficients (Kow) of selected tetrachlorobenzyltoluene (TCBT) isomers. Reported Kow values identify this substance class as very hydrophobic but the data are relatively inconsistent. Based on a series of calibration runs with hydrophobic reference substances of different chemical structure at various eluent compositions we tested different approaches for the evaluation of isocratic retention factors (logk) and found substantial differences between the direct calibration procedure at special methanol volume fractions in the mobile phase (0.95-0.80) and the use of retention factors extrapolated to pure water as eluent (logkw). The logKow values obtained for the TCBTs with the latter approach are around 0.5 units higher and closer to literature data. The gradient elution experiments yield slightly better results compared to the isocratic direct calibration procedure, but not as good as the calibration with log kw. In addition, the use of the RP-HPLC retention factors for estimating sorption coefficients (Koc) of TCBT isomers is discussed.

Benzhydryl Compounds↗

PubMed2001

Correlation of aerobic biodegradability of sulfonated azo dyes with the chemical structure.

The reported data of biodegradability of variously substituted 25 sulfonated azo dyes were divided into two classes: 8 dyes designated "rapidly biodegradable" and 17 dyes "not rapidly biodegradable", by applying principal components analysis (PCA). The biodegradability of the dyes was modeled with the discriminant technique of two-value regression analysis based on structural descriptors. A statistically significant and biologically meaningful regression model that gives perfect classification was obtained, and the results were compared with the previous qualitative interpretation of the substituent effects on biodegradation. The coefficients of the regression model revealed a significant interaction between ring substituents for biodegradability. The results facilitate understanding of the mechanism of degradation.

Azo Compounds↗

PubMed2000

Urease inhibition: a tool for toxicity identification in sediment elutriates.

A method for the detection and confirmation of heavy metal toxicants in sediment elutriates based on a urease inhibition assay, ICP-AES analysis and EDTA chelation in the frame of toxicity identification evaluation (TIE) is presented. Zinc was identified as the major toxicant in pHstat elutriates of sediments of the river Saale (Germany). Implications of natural and anthropogenic chelating agents, which are frequently present in environmental samples, on toxicity confirmation of heavy metals based on the toxic unit approach are discussed.

Environmental Monitoring↗

PubMed2000

Quantitative structure-activity analysis of the algae toxicity of nitroaromatic compounds.

Proliferation toxicity toward the algae Scenedesmus vacuolatus in a 24 h one-generation reproduction assay was determined for nitrobenzene and 18 derivatives, including two phenols. The resultant EC(50) values covering more than 4 orders of magnitude were subjected to a quantitative structure-activity analysis (QSAR) using hydrophobicity in terms of the octanol/water partition coefficient in logarithmic form, log K(ow), and 16 quantum chemical descriptors of molecular reactivity that were calculated with the AM1 scheme. For 13 mononitro derivatives and the highly hydrophobic trifluralin, a narcotic-type mode of action can explain most of the toxicity variation. Correction of log K(ow) for ionization for the phenols and quantification of the molecular susceptibility for one-electron reduction as apparently rate-determining biotransformation step by the energy of the lowest unoccupied molecular orbital, E(LUMO), yields a highly significant QSAR for all 19 compounds (r(adj)(2) = 0.90), which can be further improved when adding the maximum net atomic charge at the nitro nitrogen, q(nitro)(-)(N), as the third descriptor (r(adj)(2) = 0.93). Comparison of the energy of the singly occupied molecular orbital, E(SOMO), of the radical anions as initial metabolites with the E(SOMO) of known redox cyclers suggests that dinitrobenzenes and TFM as well as multiply chlorinated nitrobenzenes may also exert oxidative stress. This is based on an E(SOMO) window of -0.30 to 0. 55 eV as a tentative criterion for molecular structures to have the potential for redox cycling, derived from a set of eight known redox cyclers. The discussion includes a detailed analysis of apparently relevant metabolic pathways and associated modes of toxic action of nitroaromatics.

Cell Division↗

PubMed1999

Biomonitoring of airborne inorganic and organic pollutants by means of pine tree barks. I. Temporal and spatial variations.

Scots pine (Pinus sylvestris L.) bark samples were collected at two field sites (Neuglobsow, Rösa) and in different years between 1987 and 1996 in the east of Germany. The barks were analyzed with respect to the following inorganic and organic substances: Al, As, B, Ca, Cd, Ce, Cr, Cu, Fe, Hg, Mo, NH4+, Ni, NO3-, PO4(3)-, Pb, Sr, SO4(2)-, Ti, V, W, Zr, Zn, benzo[a]pyrene, fluoranthene, pyrene, alpha-hexachlorocyclohexane (alpha-HCH) and dichlorodiphenyltrichloroethane (DDT). In addition to bark samples from the site Rösa, 53 test sites were investigated in the Nature Park Dübener Heide. Here, the analysis of the barks aimed at discovering spatial patterns of the above-mentioned substances. Since 1991, most of the determined substances (e.g. sulfate, nitrate, calcium, lead, benzo[a]pyrene, alpha-HCH) show decreased concentration values in bark samples from both sites. Temporal variations reflect substantial infra-structural changes in eastern Germany, especially at Rösa and in the industrial region around the cities Leipzig, Halle, and Bitterfeld. Moreover, nitrate concentrations in barks are increasing since 1995. The trend can be explained with increased nitrogen emissions from motor traffic and livestock farms. Spatial patterns of sulphate and ammonia reflect inputs from power plants and agriculture in pine stands of the Nature Park Dübener Heide. The results show that barks of pine trees can be used as biomonitoring tools to indicate and characterize depositions of airborne organic and inorganic pollutants.

Agriculture↗

PubMed1999

Economic upheaval in 1990-93 and the ecological situation in central Germany.

German reunification in 1990 resulted in economic and social upheavals in all of the newly-formed German states. One typical example is the Leipzig-Halle-Bitterfeld region, where many of the industrial plants were fully or partly demolished for economic and technical reasons. Additionally, changes in the political climate led to the closure of a number of major military bases. Despite generally improved environmental standards, dismantling was sometimes accompanied by substantial emissions of chlorinated insecticides and other persistent organic pollutants, as is highlighted for the first time in the present paper. Our analyses are based on a regional biomonitoring net covering 7500 km2 in the Leipzig-Halle-Bitterfeld area during the time period 1990-93. The results enable increased concentrations of airborne contaminants to be attributed to processes linked to the economic upheaval of this time.

Journal Article↗

PubMed1997

Anthropogenic impacts on natural nitrogen isotope variations in Pinus sylvestris stands in an industrially polluted area.

Natural variations of the nitrogen isotopes 15N/14N (delta15N values) and the N concentrations of one-year-old needles from 7-12-year-old pine trees (Pinus sylvestris L.) were determined on 27 sites in the heavily polluted Leipzig-Halle region (former GDR). At three selected sites measurements were repeated over a period of 2 years. N concentrations and delta15N values in different needle age classes were compared at the three sites. The delta15N values of the N in the humus layer and the potential plant available N in the A(h) horizon of the local soil were determined. The 15N/14N isotope ratios (delta15N values) of one-year-old pine needles in the region of Leipzig-Halle were found to vary depending on their specific location by a factor of up to one order of magnitude (-9.6 per thousand to + 0.4 per thousand ). N concentrations in one-year-old pine needles varied between 0.71 and 1.38 mmol eq N g dw(-1). Pine stands with positive or slightly negative delta15N values and high N concentrations in one-year-old needles were concentrated around the cities of Leipzig and Halle and in the industrial areas. More negative delta15N values and lower N concentrations in one-year-old pine needles were found on sites at greater distances from the industrial agglomerations, mainly in the NE forested part. Site specific differences in the delta15N values of the N in the humus layer from three selected sites were similar to those found for the needles. No site specific differences, however, were found for the delta15N values of the water soluble nitrogen fraction from the mineral soil horizons of the same sites.

Journal Article↗

PubMed1991

First-order and pseudo-first-order elimination kinetics.

There is evidence that, for a number of chemicals, the elimination characteristics during bioconcentration do not follow monophasic first-order kinetics. In the first part of the present communication, a simple mathematical formula is presented that allows a clear-cut distinction between monophasic (pseudo-) and first-order and morephasic or higher-order elimination processes. The second part gives the mathematical description of a simple monophasic pseudo-first-order two-compartment model, which allows a quantitative kinetic analysis in the case of both initial compound and metabolite elimination.

Animals↗

PubMed1991

Acute aquatic toxicity of alkyl phenol ethoxylates.

The recently derived log Kow (octanol/water partition coefficient in logarithmic form) increment for a nonterminal oxyethylene unit was used to calculate a quantitative structure-activity relationships for literature data on the acute crustacean toxicity of polyoxyethylene surfactants. The resulting log Kow regression parameters are between the corresponding values for nonpolar and polar narcosis, which supports an interpretation of the surfactants' aquatic toxicity on the basis of another distinct mode of action. Furthermore, a comparison with calculated water solubility data indicates that for log Kow greater than 5 an aquatic toxicity decrease due to a solubility limit is expected, which gets support from two other sets on toxicity data of nonyl phenol polyethoxylates.

Animals↗

PubMed1989

Quantitative structure-activity relationships for the toxicity of selected shale oil components to mixed marine bacteria.

The toxicity of 32 shale oil components to a mixed marine bacterial culture was assessed utilizing an acute static bioassay protocol. Structure-activity relationships were examined between toxicity and 39 physicochemical properties and molecular descriptors, many of which have not been previously utilized in quantitative structure-activity relationship (QSAR) research. The toxicity could be predicted with reasonable accuracy using simple linear regression equations. However, multiparametric linear regression (MLR) equations yielded improved correlation coefficients and predictive capabilities. Such equations allow the inclusion of two or more characteristics in one relationship. The best MLR equations combined carbon number and interatomic distance between the most positive and negative charges, solubility, the approximate sigma electron density, and a variety of other parameters. These multiparametric QSARs with high predictive capabilities require computer-generated data which may not be readily available. Other MLR equations combine parameters such as the octanol water partition coefficient and the specific molecular connectivity index. These latter equations have lower correlation coefficients and yet are probably of more practical use as the data required are readily available or can be calculated. The presented multiparametric QSARs are applicable within the log Kow range of 0.6 to 5.5.

Bacteria↗

PubMed1989

Prediction of the toxicity of mixtures of shale oil components.

The toxicities of selected oil shale components and of mixtures of these components to a mixed marine bacterial culture have been determined. The toxicities of mixtures whose components were members of the same homologous series were found to be additive. In all other cases, even when the compounds were as closely related as structural isomers, synergism was observed. Simple and multiple linear regression equations utilizing measures of toxicity and molecular descriptors were used successfully to predict the enhancement of toxicity due to interaction of components in mixtures regardless of the mode of interaction.

Bacteria↗

PubMed1988

Evaluation of various molecular parameters as predictors of bioconcentration in fish.

A reliable set of data on the bioconcentration factors (KB) of a diverse range of compounds in fish was selected from the literature. Using the structures of these compounds, the following molecular parameters were calculated: molecular weight (MW), solvent accessible molecular surface area (SASA), solvent accessible molecular volume (SAV), molar refraction (MR), largest principal moment of inertia (LPMI) and several molecular connectivity indices of the Randić type (1 chi, 2 chi, 3 chi, 1 chi vr, 3 chi c). The relationships between these parameters and log KB were evaluated for all compounds and the following subgroups: chlorinated hydrocarbons (CHC), polyaromatic hydrocarbons (PAH), and CHC and PAH combined. These relationships indicated that SASA, SAV, and MR were good predictors of log KB for the CHC and PAH combined or alone and the other parameters were less satisfactory with these groups. In addition with the CHC, the log of these parameters displayed an improved correlation with log KB due to apparent nonlinearity in the log to linear relationship. Thus, with these groups of compounds, calculated values of SASA, SAV, and MR provide a satisfactory means of estimating log KB without measured data.

Animals↗