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W Baeyens

Publications and source records attributed to W Baeyens.

At least 19 recordsLinked to original sources
PubMed2007

High resolution profiles of thallium, manganese and iron assessed by DET and DGT techniques in riverine sediment pore waters.

High resolution profiles of Mn, Tl and Fe concentrations have been assessed in the pore waters of river Leie sediments at Warneton and Menen (at the border of Belgium and France) by DET (Diffusive Equilibrium in Thin Films) and DGT (Diffusive Gradients in Thin Films) techniques. The oxidized, solid Mn (IV), Tl (III) and Fe (III) compounds were reduced in the suboxic (+255 to -20 mV versus Standard Hydrogen Electrode (SHE)) riverine sediments and since these reduced species are much more soluble also they are released into the pore waters. The highest DET (total dissolved) concentrations of Fe (76 mg l(-1)), Mn (2 mg l(-1)) were observed at the station of Menen, while Tl maxima differed only slightly between the 3 surveys (21 to 27 microg l(-1)). The average ratios of Fe/Mn/Tl in the pore waters at the 3 sampling stations are fairly constant for both the DET and DGT samplings. However, the results indicate that compared to Fe and Tl a greater proportion of the Mn measured by DET is accumulated by DGT, reflecting the ready supply of Mn from solid phase to solution.

Belgium↗
PubMed2006

High-resolution profiles of trace metals in the pore waters of riverine sediment assessed by DET and DGT.

The techniques of DET (diffusive equilibrium in thin films) and DGT (diffusive gradients in thin films) were applied to obtain high-resolution vertical profiles of trace metals in freshwater sediments. In the framework of the EU-Interreg project Stardust (http://www.vliz.be/projects/stardust/) between France and Belgium, in which the mobility of sediment bound metals is investigated, sediment samples were collected from the Upper Scheldt River (at Helkijn, Belgium) and the Leie River (at Warneton, located at the Belgian-French border). Intra- and inter-laboratory comparisons of the gel techniques were carried out between the two laboratories involved. In general, a good agreement was observed, taking sediment heterogeneity into account. At both stations, metal pore water profiles show more or less similar tendencies although the sediment at Warneton was more anoxic than at Helkijn. A strong correlation between Fe and Co was found at Helkijn as well as at Warneton. The metal gradients at the water/sediment interface were calculated from the high resolution profiles and the conventional, low resolution profiles. Significant differences were observed.

Arsenic↗
PubMed2005

Heavy metals in Lake Balaton: water column, suspended matter, sediment and biota.

During the period 1999-2002, five sampling cruises have been carried out on Lake Balaton to assess trace metal distribution in the lake and to identify major sources. Eighteen elements, including Cr, Co, Ni, Cu, Zn, Cd, Pb (trace metals) and Al, Ba, Ca, Fe, K, Mg, Mn, Na, P, S, Sr (major metals), were determined in one or more of the lake's compartments. Lower trace metal concentrations in rainwater were observed in June and February 2000, while much higher levels were present in September 2001 (during a storm event) and in snow (February 2000). In the Northern and Western parts of the lake, especially at the inflow of river Zala and the locations of the yacht harbours, metal concentrations were higher in almost all compartments. Because the lake is very shallow, storm conditions also change significantly the metal distributions in the dissolved and particulate phases. The Kis-Balaton protection system located on Zala river functions very efficiently for retaining suspended particulate matter (SPM; 72% retention) and associated metals. Metal concentrations in surface sediments of the lake showed a high variability. After normalisation for the fine sediment fraction, only a few stations including Zala mouth appeared to be enriched in trace metals. In zooplankton, Zn seemed to be much more elevated compared to the other trace metals. Based on the molar ratios of the trace metals in the various compartments and input flows of the lake, several trends could be deduced. For example, molar ratios of the trace metals in the dissolved and solid (suspended particulate matter and sediments) phases in the lake are fairly similar to those in Zala River.

Animals↗
PubMed2005

Mercury distribution and speciation in Lake Balaton, Hungary.

The distribution and speciation of mercury in air, rain, lake water, sediment, and zooplankton in Lake Balaton (Hungary) were investigated between 1999 and 2002. In air, total gaseous mercury (TGM) ranged from 0.4 to 5.9 ng m(-3) and particulate phase mercury (PPM) from 0.01 to 0.39 ng m(-3). Higher concentrations of both TGM and PPM occurred during daytime. Higher concentrations of PPM occurred in winter. In rain and snow, total mercury ranged from 10.8 to 36.7 ng L(-1) in summer but levels up to 191 ng L(-1) in winter. Monomethylmercury (MMHg) concentrations ranged from 0.09 to 1.26 ng L(-1) and showed no seasonal variations. Total Hg in the unfiltered lake water varied spatially, with concentrations ranging from 1.4 to 6.5 ng L(-1). Approximately 70% of the total Hg is dissolved. MMHg levels ranged from 0.08 to 0.44 ng L(-1) as total and from 0.05 to 0.37 ng L(-1) in the dissolved form. Lower Hg concentrations in the water column occurred in winter. In suspended particulate matter and in sediment, total mercury ranged from 9 to 160 ng g(-1) dw, and MMHg ranged from 0.07 to 0.84 ng g(-1) dw. In zooplankton, an average mercury level of 31.0+/-6.8 ng g(-1) dw occurred, with MMHg accounting for approximately 17%. In sediments, suspended-matter- and zooplankton-high Hg and MMHg levels occurred at the mouth of the River Zala, but, in the lake, higher concentrations occurred on the Northern side, and an increasing trend from north-west to north-east was observed. In general, regarding Hg, Lake Balaton can be considered as a relatively uncontaminated site. The high-pH and well-oxygenated water as well as the low organic matter content of the sediment does not favour the methylation of Hg. In addition, bioconcentration and bioaccumulation factors are relatively low compared to other aquatic systems.

Air Pollutants↗
PubMed2005

Organotin analysis by gas chromatography-pulsed flame-photometric detection (GC-PFPD).

Monobutyltin (MBuT), dibutyltin (DBuT), and tributyltin (TBuT) mixtures have been separated and quantified by gas chromatography with pulsed flame-photometric detection (GC-PFPD). The compounds were first derivatized with NaBEt4, then extracted with hexane and injected into the GC in splitless mode. Optimum GC and detector conditions were established. For GC, various injector temperatures and oven temperature programs were tested. For the PFPD detector, gate settings (gate delay and gate width) and detector temperature were optimized. A very good linearity was obtained up to 100-150 ppb for all organotin compounds. The detection limits obtained were: MBuT (0.7 ppb), DBuT (0.8 ppb), and TBuT (0.6 ppb). RSD for repeatability and reproducibility were well below 20% when the instrument was in routine operation. A biological sample (CRM 477) was also analyzed for organotins. Extraction from the biological matrix was performed with TMAH. Besides the increased risk of contamination, the derivatization step seemed to be critical. pH and amount of derivatizing agent were tested. When using an internal standard (TPrT) between 90% and 110% of the certified amounts of organotin were recovered.

Animals↗
PubMed2003

Determination of methylmercury in environmental samples using static headspace gas chromatography and atomic fluorescence detection after aqueous phase ethylation.

A rapid and automated method for the determination of monomethylmercury (MMHg) in environmental samples was developed using headspace gas chromatography with atomic fluorescence detection in combination with aqueous phase ethylation. Sample preparation steps were optimized for sediments, biological samples, and water samples using certified reference materials and real samples with a broad range of MMHg concentrations. Different extraction procedures were compared for both sediments and biological samples. The methods were applied in the intercomparison exercises for the certification of MMHg in sediments (IAEA 405) and in Oyster tissue (BCR 710) and the results were accepted for certification. The detection limits for MMHg are 0.002 ng Hg/g for sediments and biological samples and 0.01 ng Hg/L for water samples. The method was tested for methylation artifacts; no artifact was observed in the sediment samples and CRMs tested.

Journal Article↗
PubMed2003

Evalution of sequential extractions on dry and wet sediments.

A five-step sequential extraction procedure was applied on dried and wet Ballastplaat Scheldt estuary sediments. When wet (fresh) sediments were used, all sample handling up to the 3rd extraction step, inclusive, was carried out under inert atmosphere. The repeatability of the procedure was very good on dry samples. For Fe as for Mn, RSD values are lower than 4%, except for Mn in the fifth extraction step where a spread of 10% is observed. The observed RSDs for Pb are of the same order of magnitude as those for Mn. On wet samples the spread of the results is higher than on dried ones. The highest RSDs observed for Fe amount to 20%, for Mn to 15% but for Pb an RSD of up to 44% was found. Better homogenization of the solid sediment part of lyophilized sediments and different porosities of wet sediment sub-samples may be the explanation. These results also indicated that drying/oxidizing of the sediment sample causes a shift from less available/mobile metal fractions to more available/mobile fractions. The Mn and Fe oxyhydroxide spikes added to a wet sediment sample were recovered between 100+/-10%. The results obtained after changing the sequence of the extraction steps (multiple rotations and inversions were tested) corroborated the progressive increase in the aggressive nature of the extraction solutions in our standard scheme. Although there is also no need to change the ratio volume of extractant to amount of sediment, increasing the number of extraction repetitions in steps 1 to 3 resulted, for some of those extraction steps, in a partially modified analyte distribution. Finally the method was applied to sandy and muddy sediment cores of the Scheldt estuary and revealed clear differences between metal distributions in both types of sediment.

Journal Article↗
PubMed2003

Bioconcentration and biomagnification of mercury and methylmercury in North Sea and Scheldt estuary fish.

Total Hg and MMHg concentrations were assessed in more than 350 fish and shellfish samples. Hg concentrations in Greater North Sea fish of prey range from 0.039 mg kg(-1) wet weight (ww; for ray) to 0.61 mg kg(-1) ww (for dogfish) and for all other fish species, from 0.045 mg kg(-1) ww (for plaice) to 0.33 mg kg(-1) ww (for sand sole), with 95 +/- 2% of the Hg content in the MMHg form. In Belgian coastal zone, fish concentrations range from 0.063 mg kg(-1) ww for plaice to 0.13 mg kg(-1) ww for flounder, with 82-87% of the Hg content in the MMHg form. In fish of the Scheldt, which is a very polluted estuary, Hg levels, as well as the percent MMHg of the total Hg, were lower than in the two zones previously mentioned. The intraspecies variability is of the order of 50% in each of the three zones. In liver tissue, a much larger variability was observed than in muscle tissue, except for fish species of the Scheldt. In most cases, the MMHg fraction in a particular fish species is inversely related to the intraspecies variability. Bioconcentration and biomagnification factors (BCF and BMF, respectively) were assessed. MMHg-BMFs were a few orders of magnitude higher than Hg(inorganic)-BMFs, and for the same species were always highest in the Greater North Sea and lowest in the Scheldt. For each of the Belgian coastal zone four species, a weak positive correlation between Hg content and fish length was found; however, the larger the size-range, the better the correlation. Taking fish length into account, a statistically significant difference in contamination level was observed for species sampled from the different geographical zones.

Animals↗
PubMed2002

Total and toxic arsenic levels in north sea fish.

Levels of arsenic contamination in muscle and liver tissue of 25 sea fish and 4 shellfish species from the North Sea were determined. Analyses were done by both ICP-MS and HG-AFS to distinguish between nontoxic and toxic fractions of As. Highest total As concentrations were found in lemon sole, dogfish, ray, and witch. Average total As concentrations in these fish species were higher than 20 mg kg(-1) WW. The same species as well as the other flatfishes contained the highest amounts of toxic As (> 0.1 mg kg(-1) WW). Toxic fractions (AsTox/AsT%) above 2% were found in the following six species: seabass, ling, john dory, pouting, dab, and brill. No preferential concentration in the liver compared to the muscle was observed. In a worst-case scenario (when fish has been dried or smoked and the toxic As level is high; for example 0.5 mg kg(-1) WW), the As content of North Sea marine food may reach harmful levels. A normalization reflecting the toxic potential of sea fish was made. Shark and ray and most flatfish species have positive (high) normalized AsTox values.By ANOVA testing we compared the individual AsT concentrations of samples of the same species (intraspecies variability). Significant differences for some fish species were observed; significantly higher AsT concentrations were found in dogfish from the French coast versus the western North Sea and in common sole from the Bay of the Seine, in the north of France, versus the western North Sea.

Animals↗
PubMed2000

Cadmium and lead concentrations in acid food simulants: the values of validation parameters are predominantly affected by interspecific differences of utensils.

The obvious toxicity of cadmium and lead is at the basis of compulsory concentration determinations for lixiviation solutions of ceramic and earthenware household receptacles such as cups, plates, bowls and others. Concentrations in the food simulant which exceed 0.100 +/- 0.005 mg Cd dm-2 and 1.00 +/- 0.05 mg Pb dm-2 for flat receptacles, 0.500 +/- 0.025 mg Cd l-1 and 5.00 +/- 0.25 mg Pb l-1 for low volume (< 5 l) receptacles and 0.250 +/- 0.025 mg Cd l-1 and 2.50 +/- 0.25 mg Pb l-1 for high volume (> 5 l) receptacles are not acceptable and measures were taken by the EU member state authorities to enforce these norm concentrations. Generally, the uncertainty on the results forwarded by the legislation amounts to 5%. This value does not at all match the pronounced variability observed for several 'identical' trade samples, but rather represents the inherent variability of spectrometric analyses alone. Considering that the coefficients of variation can be as high as approximately 30%, either the ranges of acceptable concentrations or the maximal allowable concentrations should be corrected. Aware of the negative health effects of heavy metal contamination and of the risk increase due to dietary intake, a downward adjustment of the acceptable concentration ranges to 0.07 mg Cd dm-2 +/- 12%, 0.30 mg Cd l-1 +/- 12% and 0.10 mg Cd l-1 +/- 12% and to 0.8 mg Pb dm-2 +/- 13%, 4.0 mg Pb l-1 +/- 13% and 1.50 mg Pb l-1 +/- 13% is suggested.

Cadmium↗
PubMed1999

Bioavailability of racemic ketoprofen in healthy horses following rectal administration.

Ketoprofen (KTP) is a chiral non-steroidal anti-inflammatory drug (NSAID) of the propionic acid class, approved by the FDA for the allevation of pain associated with musculoskeletal disorders in horses. The present study was designed to examine the bioavailability of ketoprofen enantiomers after rectal administration of the racemate to healthy horses. One gram of racemic ketoprofen was injected intravenously and administered rectally as a fat based suppository in a cross-over design study (n = 4). Blood samples were analysed for KTP enantiomers using HPLC. After IV administration, the S(+) enantiomer concentrations in plasma were higher than the R(-) enantiomer concentrations and the AUC(0-12 h) for the S(+) enantiomer was significantly higher than for the R(-) enantiomer. Following rectal administration C(max) and AUC(0-12 h) were significantly higher for the S(+) than for the R(-) enantiomer. Bioavailability after rectal administration was low. Since there was no significant difference in bioavailability between the two enantiomers, it is assumed that no pre-systemic inversion from R(-) to S(+) occurred after rectal administration of racemic KTP to horses.

Administration, Rectal↗
PubMed1998

Effect of the siderophore alcaligin E on the bioavailability of Cd to Alcaligenes eutrophus CH34.

Alcaligin E, the siderophore of the heavy metal-resistant A. eutrophus strain CH34, was shown to interact with Cd and consequently affect its bioavailability and toxicity. The addition of alcaligin E markedly stimulated the growth in the presence of Cd of an alcaligin E-deficient CH34 derivative. Using bioluminescence assays, this effect could be assigned to a decrease in bioavailability of Cd in the presence of alcaligin E. However, Cd-uptake studies showed no influence of alcaligin E on the cellular concentration of Cd. Furthermore, by scanning electron microscopy, the morphology of precipitated Cd crystals was shown to be altered by alcaligin E. These data suggest that alcaligin E, besides its function in iron supply to the cell, provides a protection against heavy metal toxicity. A link between the A. eutrophus CH34 siderophore system and the czc-mediated Cd-efflux system is hypothesized.

Alcaligenes↗
PubMed1998

HPLC on Chiralcel OJ-R for enantiomer separation and analysis of ketoprofen, from horse plasma, as the 9-aminophenanthrene derivative.

Racemic ketoprofen is a non-steroidal anti-inflammatory drug used to treat musculoskeletal and colic conditions in horses. The enantioselective chiral inversion of ketoprofen administered to horses has been studied by use of cellulose tris(4-methylbenzoate), also known as Chiralcel OJ-R, as chiral stationary phase; acetonitrile - 0.02 M perchlorate buffer (pH 2.0)-methanol, 60:15:25 (v/v/v) was used as mobile phase. Before chromatography, to effect adequate chiral interaction with the chiral stationary phase ketoprofen was derivatized with 9-aminophenanthrene, under acid conditions, after solid-phase (C18) extraction and then liquid-liquid extraction, to ensure effective removal of endogenous plasma materials. The 9-aminophenanthrene derivative of S-ibuprofen was used as internal standard. The enantiomers of ketoprofen were separated to baseline (Rs = 6.44, alpha = 1.76) within a short analysis time. The results indicate that the bio-inversion of R-ketoprofen to the S isomer is significant in equine species. However, considerable differences in pharmacokinetic parameters were observed, indicating large inter-animal variation.

Animals↗
PubMed1997

Two-component regulatory system involved in transcriptional control of heavy-metal homoeostasis in Alcaligenes eutrophus.

The czc determinant, which mediates resistance to Co2+, Zn2+ and Cd2+ in Alcaligenes eutrophus CH34 by cation efflux, is regulated by a two-component regulatory system composed of the sensor histidine kinase CzcS and the response activator CzcR (in addition to other components previously described). Regulatory genes are arranged in an upstream regulatory region (URR) and a downstream regulatory region (DRR). Transcription of czcCBA and of the URR was regulated by heavy-metal cations. DNA sequencing of the region downstream of czcD revealed the presence of the czcR and czcS genes which together with czcD form the DRR. Regulation of the DRR was studied with a czcD::lacZ translational fusion and a czcS::lux transcriptional fusion. Expression of both genes is also regulated by heavy metals. The genes of the URR yielded three mRNAs of approx. 1200, 500 and 200 nucleotides, respectively. The genes czcCBA for the cation/proton antiporter CzcCBA were transcribed by one operon as a transcript of 6200 nucleotides.

Alcaligenes↗
PubMed1996

Bioavailability of ketoprofen in horses after rectal administration.

Six healthy mares ranging in age from 6 to 12 years and weighing from 415 to 540 kg were used to determine the rectal bioavailability of ketoprofen. For the rectal administration, three different formulations, each containing 1 g of ketoprofen, were administered in a fatty and a hydrophilic suppository base and as a liquid suspension. An average elimination half-life of 1.3 h (+/-1.2) was found. The average value for the total plasma clearance (ClT) was 131.9mL/ min.kg (range 95-183.5). The volume of distribution Vd(area) was 255 mL/kg and the mean residence time (MRT) value was 0.47 h. After rectal administration, the mean maximal plasma ketoprofen concentrations were 1.6(+/-0.8), 1.1(+/-0.7) and 1.6(+/-0.2) micrograms/mL for the fatty suppository, the hydrophilic suppository and the liquid suspension respectively. The absolute bioavailability of ketoprofen in horses after rectal administration of the three formulations was relatively low, with a large interindividual variability (24.5 +/- 9.5%, 28.7 +/- 18% and 31.3 +/- 6.8% for the fatty suppository, the hydrophilic suppository and the liquid suspension respectively). These values were not significantly different (P = 0.05; Friedman test). Despite the low rectal bioavailability obtained in this study, there was some evidence for the clinical effectiveness of the rectal formulations.

Administration, Rectal↗
PubMed1995

The czc operon of Alcaligenes eutrophus CH34: from resistance mechanism to the removal of heavy metals.

The plasmid-borne czc operon ensures for resistance to Cd2+, Zn2+ and Co2+ ions through a tricomponent export pathway and is associated to various conjugative plasmids of A. eutrophus strains isolated from metal-contaminated industrial areas. The czc region of pMOL30 was reassessed especially for the segments located upstream and downstream the structural genes czc CBA. In cultures grown with high concentrations of heavy metals, czc-mediated efflux of cations is followed by a process of metal bioprecipitation. These observations led to the development of bioreactors designed for the removal of heavy metals from polluted effluents.

ATP-Binding Cassette Transporters↗
PubMed1994

The determination of non-steroidal antiinflammatory drugs in pharmaceuticals by capillary zone electrophoresis and micellar electrokinetic capillary chromatography.

Ibuprofen, indomethacin, ketoprofen, piroxicam and diclofenac have been quantified in dragees, suspension, suppositories, capsules, injection solutions and tablets by capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MEKC). The experiments were performed without specific sample pretreatment. The reproducibility of the method was investigated. Good quantitation was obtained in short analysis times. CE and MEKC are found to offer a good alternative to conventional HPLC methods.

Anti-Inflammatory Agents, Non-Steroidal↗