Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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    Framework to determine the effectiveness of dietary exposure mitigation to chemical contaminants
    Fels, H.J. van der; Edwards, S. ; Kennedy, M. ; O'Hagan, A. ; O'Mahony, C. ; Scholz, G. ; Steinberg, P. ; Tennant, D. ; Chiodini, A. - \ 2014
    Food and Chemical Toxicology 74 (2014). - ISSN 0278-6915 - p. 360 - 371.
    chromatography-mass spectrometry - solid-phase microextraction - extraction-gas chromatography - single-laboratory validation - fusarium mycotoxin content - methyl mercury exposure - spme-gc-ms - risk-assessment - baby-food - fish consumption
    In order to ensure the food safety, risk managers may implement measures to reduce human exposure to contaminants via food consumption. The evaluation of the effect of a measure is often an overlooked step in risk analysis process. The aim of this study was to develop a systematic approach for determining the effectiveness of mitigation measures to reduce dietary exposure to chemical contaminants. Based on expert opinion, a general framework for evaluation of the effectiveness of measures to reduce human exposure to food contaminants was developed. The general outline was refined by application to three different cases: 1) methyl mercury in fish and fish products, 2) deoxynivalenol in cereal grains, and 3) furan in heated products. It was found that many uncertainties and natural variations exist, which make it difficult to assess the impact of the mitigation measure. Whenever possible, quantitative methods should be used to describe the current variation and uncertainty. Additional data should be collected to cover natural variability and reduce uncertainty. For the time being, it is always better for the risk manager to have access to all available information, including an assessment of uncertainty; however, the proposed methodology provides a conceptual framework for addressing these systematically.
    Sports doping: Emerging designer and therapeutic B2-agonists
    Fragkaki, A.G. ; Georgakopoulos, C. ; Sterk, S.S. ; Nielen, M.W.F. - \ 2013
    Clinica Chimica Acta 425 (2013). - ISSN 0009-8981 - p. 242 - 258.
    acting beta(2)-adrenoreceptor agonists - chromatography-mass spectrometry - molecularly imprinted polymers - obstructive pulmonary-disease - beta-adrenergic agonists - performance liquid-chromatography - 2-dimensional gas-chromatography - developed bronchodilati
    Beta2-adrenergic agonists, or ß2-agonists, are considered essential bronchodilator drugs in the treatment of bronchial asthma, both as symptom-relievers and, in combination with inhaled corticosteroids, as disease-controllers. The use of ß2-agonists is prohibited in sports by the World Anti-Doping Agency (WADA) due to claimed anabolic effects, and also, is prohibited as growth promoters in cattle fattening in the European Union. This paper reviews the last seven-year (2006-2012) literature concerning the development of novel ß2-agonists molecules either by modifying the molecule of known ß2-agonists or by introducing moieties producing indole-, adamantyl- or phenyl urea derivatives. New emerging ß2-agonists molecules for future therapeutic use are also presented, intending to emphasize their potential use for doping purposes or as growth promoters in the near future.
    Chronic Wasting Disease in Bank Voles: Characterisation of the Shortest Incubation Time Model for Prion Diseases
    Bari, M.A. Di; Nonno, R. ; Castilla, J. ; Augostino, C. D'; Pirisinu, L. ; Riccardi, G. ; Conte, M. ; Richt, J.A. ; Kunkle, R. ; Langeveld, J.P.M. ; Vaccari, G. ; Agrimi, U. - \ 2013
    PLoS Pathogens 9 (2013)3. - ISSN 1553-7366
    chromatography-mass spectrometry - misfolding cyclic amplification - creutzfeldt-jakob-disease - cervus-elaphus-nelsoni - in-vitro generation - transgenic mice - spongiform encephalopathy - mule deer - species-barrier - protein allotypes
    In order to assess the susceptibility of bank voles to chronic wasting disease (CWD), we inoculated voles carrying isoleucine or methionine at codon 109 (Bv109I and Bv109M, respectively) with CWD isolates from elk, mule deer and white-tailed deer. Efficient transmission rate (100%) was observed with mean survival times ranging from 156 to 281 days post inoculation. Subsequent passages in Bv109I allowed us to isolate from all CWD sources the same vole-adapted CWD strain (Bv109ICWD), typified by unprecedented short incubation times of 25–28 days and survival times of ~35 days. Neuropathological and molecular characterisation of Bv109ICWD showed that the classical features of mammalian prion diseases were all recapitulated in less than one month after intracerebral inoculation. Bv109ICWD was characterised by a mild and discrete distribution of spongiosis and relatively low levels of protease-resistant PrPSc (PrPres) in the same brain regions. Despite the low PrPres levels and the short time lapse available for its accumulation, end-point titration revealed that brains from terminally-ill voles contained up to 108,4 i.c. ID50 infectious units per gram. Bv109ICWD was efficiently replicated by protein misfolding cyclic amplification (PMCA) and the infectivity faithfully generated in vitro, as demonstrated by the preservation of the peculiar Bv109ICWD strain features on re-isolation in Bv109I. Overall, we provide evidence that the same CWD strain was isolated in Bv109I from the three-cervid species. Bv109ICWD showed unique characteristics of “virulence”, low PrPres accumulation and high infectivity, thus providing exceptional opportunities to improve basic knowledge of the relationship between PrPSc, neurodegeneration and infectivity.
    Genetic analysis of metabolome-phenotype interactions: from model to crop species
    Carreno Quintero, N. ; Bouwmeester, H.J. ; Keurentjes, J.J.B. - \ 2013
    Trends in Genetics 29 (2013)1. - ISSN 0168-9525 - p. 41 - 50.
    quantitative trait loci - genome-wide association - chromatography-mass spectrometry - functional genomics - arabidopsis-thaliana - mapping population - systems biology - glucosinolate accumulation - secondary metabolism - transcription factor
    The past decade has seen increased interest from the scientific community, and particularly plant biologists, in integrating metabolic approaches into research aimed at unraveling phenotypic diversity and its underlying genetic variation. Advances in plant metabolomics have enabled large-scale analyses that have identified qualitative and quantitative variation in the metabolic content of various species, and this variation has been linked to genetic factors through genetic-mapping approaches, providing a glimpse of the genetic architecture of the plant metabolome. Parallel analyses of morphological phenotypes and physiological performance characteristics have further enhanced our understanding of the complex molecular mechanisms regulating these quantitative traits. This review aims to illustrate the advantages of including assessments of phenotypic and metabolic diversity in investigations of the genetic basis of complex traits, and the value of this approach in studying agriculturally important crops. We highlight the ground-breaking work on model species and discuss recent achievements in important crop species.
    Identifying genotype-by-environment interactions in the metabolism of germinating Arabidopsis seeds using Generalized Genetical Genomics
    Joosen, R.V.L. ; Arends, D. ; Li, Y. ; Willems, L.A.J. ; Keurentjes, J.J.B. ; Ligterink, W. ; Jansen, R.C. ; Hilhorst, H.W.M. - \ 2013
    Plant Physiology 162 (2013)2. - ISSN 0032-0889 - p. 553 - 566.
    quantitative trait loci - chromatography-mass spectrometry - heterogeneous inbred family - natural allelic variation - controlling root-growth - plant development - line population - complex traits - potato-tuber - thaliana
    A complex phenotype such as seed germination is the resultant of several genetic and environmental cues and requires the concerted action of many genes. The use of well-structured recombinant inbred lines in combination with omics analysis can help to disentangle the genetic basis of such quantitative traits. This so called genetical genomics approach can effectively capture both genetic (G) and epistatic interactions (G:G). However, to understand how the environment interacts with genomic encoded information (G:E) a better understanding of the perception and processing of environmental signals is needed. In a classical genetical genomics setup this requires replication of the whole experiment in different environmental conditions. A novel generalized setup overcomes this limitation and includes environmental perturbation within a single experimental design. We developed a dedicated QTL mapping procedure to implement this approach and used existing phenotypical data to demonstrate its power. Additionally, we studied the genetic regulation of primary metabolism in dry and imbibed Arabidopsis seeds. Many changes were observed in the metabolome which are both under environmental and genetic control and their interactions. This concept offers unique reduction of experimental load with minimal compromise of statistical power and is of great potential in the field of systems genetics which requires a broad understanding of both plasticity and dynamic regulation.
    Safety assessment of smoke flavouring primary products by the European Food Safety Authority
    Theobald, A. ; Arcella, D. ; Carere, A. ; Croera, C. ; Engel, K.H. ; Gott, D. ; Gurtler, R. ; Meier, D. ; Pratt, I. ; Rietjens, I.M.C.M. ; Simon, R. ; Walker, R. - \ 2012
    Trends in Food Science and Technology 27 (2012)2. - ISSN 0924-2244 - p. 97 - 108.
    polycyclic aromatic-hydrocarbons - chromatography-mass spectrometry - discriminate rodent carcinogens - vitro genotoxicity tests - flue-gas smoking - in-vitro - oncorhynchus-mykiss - meat-products - condensate - battery
    This paper summarises the safety assessments of eleven smoke flavouring primary products evaluated by the European Food Safety Authority (EFSA). Data on chemical composition, content of polyaromatic hydrocarbons and results of genotoxicity tests and subchronic toxicity studies are presented and discussed. The smoke flavourings vary in their contents of identified constituents; none of them exceeded the legal limit for benzo[a]pyrene and benzo[a]anthracene. Ten smoke flavourings proved not to be genotoxic in vivo, whereas this could not be ruled out for another smoke flavouring. Results from animal testing and proposed dietary exposure indicate that only three smoke flavourings would not be of safety concern for humans.
    Untargeted Metabolic Quantitative Trait Loci Analyses Reveal a Relationship between Primary Metabolism and Potato Tuber Quality
    Carreno Quintero, N. ; Acharjee, A. ; Maliepaard, C.A. ; Bachem, C.W.B. ; Mumm, R. ; Bouwmeester, H.J. ; Visser, R.G.F. ; Keurentjes, J.J.B. - \ 2012
    Plant Physiology 158 (2012)3. - ISSN 0032-0889 - p. 1306 - 1318.
    chromatography-mass spectrometry - arabidopsis-thaliana - starch degradation - late blight - amino-acid - enzymatic discoloration - biochemical networks - introgression lines - genetic genomics - candidate genes
    Recent advances in -omics technologies such as transcriptomics, metabolomics, and proteomics along with genotypic profiling have permitted dissection of the genetics of complex traits represented by molecular phenotypes in nonmodel species. To identify the genetic factors underlying variation in primary metabolism in potato (Solanum tuberosum), we have profiled primary metabolite content in a diploid potato mapping population, derived from crosses between S. tuberosum and wild relatives, using gas chromatography-time of flight-mass spectrometry. In total, 139 polar metabolites were detected, of which we identified metabolite quantitative trait loci for approximately 72% of the detected compounds. In order to obtain an insight into the relationships between metabolic traits and classical phenotypic traits, we also analyzed statistical associations between them. The combined analysis of genetic information through quantitative trait locus coincidence and the application of statistical learning methods provide information on putative indicators associated with the alterations in metabolic networks that affect complex phenotypic traits.
    Volatile compound fingerprinting of mixed cultutre fermentations
    Bok, F.A.M. de; Janssen, P.W.M. ; Bayjanov, J.R. ; Sieuwerts, S. ; Lommen, A. ; Hylckama, J. van; Molenaar, D. - \ 2011
    Applied and Environmental Microbiology 77 (2011)17. - ISSN 0099-2240 - p. 6233 - 6239.
    chromatography-mass spectrometry - solid-phase microextraction - starter cultures - flavor - metabolomics - yogurt - identification - genomics - strains - tomato
    With the advent of the -omics era, classical technology platforms, such as hyphenated mass spectrometry, are currently undergoing a transformation toward high-throughput application. These novel platforms yield highly detailed metabolite profiles in large numbers of samples. Such profiles can be used as fingerprints for the accurate identification and classification of samples as well as for the study of effects of experimental conditions on the concentrations of specific metabolites. Challenges for the application of these methods lie in the acquisition of high-quality data, data normalization, and data mining. Here, a high-throughput fingerprinting approach based on analysis of headspace volatiles using ultrafast gas chromatography coupled to time of flight mass spectrometry (ultrafast GC/TOF-MS) was developed and evaluated for classification and screening purposes in food fermentation. GC-MS mass spectra of headspace samples of milk fermented by different mixed cultures of lactic acid bacteria (LAB) were collected and preprocessed in MetAlign, a dedicated software package for the preprocessing and comparison of liquid chromatography (LC)-MS and GC-MS data. The Random Forest algorithm was used to detect mass peaks that discriminated combinations of species or strains used in fermentations. Many of these mass peaks originated from key flavor compounds, indicating that the presence or absence of individual strains or combinations of strains significantly influenced the concentrations of these components. We demonstrate that the approach can be used for purposes like the selection of strains from collections based on flavor characteristics and the screening of (mixed) cultures for the presence or absence of strains. In addition, we show that strain-specific flavor characteristics can be traced back to genetic markers when comparative genome hybridization (CGH) data are available.
    Identification of Genes in the Phenylalanine Metabolic Pathway by Ectopic Expression of a MYB Transcription Factor in Tomato Fruit
    Cin, V. Dal; Tieman, D.M. ; Tohge, T. ; McQuinn, R. ; Vos, C.H.R. de; Osorio, S. ; Schmelz, E.A. ; Taylor, M.G. ; Smits-Kroon, M.T. ; Schuurink, R.C. ; Haring, M.A. ; Giovannoni, J. ; Fernie, A.R. ; Klee, H.J. - \ 2011
    The Plant Cell 23 (2011)7. - ISSN 1040-4651 - p. 2738 - 2753.
    chromatography-mass spectrometry - prephenate aminotransferase - amino-acids - lycopersicon-esculentum - arabidopsis-thaliana - escherichia-coli - microarray data - cell-cultures - biosynthesis - arogenate
    Altering expression of transcription factors can be an effective means to coordinately modulate entire metabolic pathways in plants. It can also provide useful information concerning the identities of genes that constitute metabolic networks. Here, we used ectopic expression of a MYB transcription factor, Petunia hybrida ODORANT1, to alter Phe and phenylpropanoid metabolism in tomato (Solanum lycopersicum) fruits. Despite the importance of Phe and phenylpropanoids to plant and human health, the pathway for Phe synthesis has not been unambiguously determined. Microarray analysis of ripening fruits from transgenic and control plants permitted identification of a suite of coregulated genes involved in synthesis and further metabolism of Phe. The pattern of coregulated gene expression facilitated discovery of the tomato gene encoding prephenate aminotransferase, which converts prephenate to arogenate. The expression and biochemical data establish an arogenate pathway for Phe synthesis in tomato fruits. Metabolic profiling and 13C flux analysis of ripe fruits further revealed large increases in the levels of a specific subset of phenylpropanoid compounds. However, while increased levels of these human nutrition-related phenylpropanoids may be desirable, there were no increases in levels of Phe-derived flavor volatiles.
    Screening of transformation products in soils contaminated with unsymmetrical dimethylhydrazine using headspace SPME and GC-MS
    Kenessov, B.N. ; Koziel, J.A. ; Grotenhuis, J.T.C. ; Carlsen, L. - \ 2010
    Analytica Chimica Acta 674 (2010)1. - ISSN 0003-2670 - p. 32 - 39.
    solid-phase microextraction - chromatography-mass spectrometry - volatile organic-compounds - gas-chromatography - olfactometry - air - 1,1-dimethylhydrazine - odorants
    The paper describes a novel SPME-based approach for sampling and analysis of transformation products of highly reactive and toxic unsymmetrical dimethylhydrazine (UDMH) which is used as a fuel in many Russian, European, Indian, and Chinese heavy cargo carrier rockets. The effects of several parameters were studied to optimize analyte recovery. It was found that the 85 µm Carboxen/polydimethylsiloxane fiber coating provides the highest selectivity for selected UDMH transformation products. Optimal sampling/sample preparation parameters were determined to be 1-h soil headspace sampling time at 40 °C. The GC inlet temperature was optimized to 170 °C held for 0.1 min, then 1 °C s-1 ramp to 250 °C where it was held for 40 min. Temperature programing resulted in a fast desorption along with minimal chemical transformation in the GC inlet. SPME was very effective extracting UDMH transformation products from soil samples contaminated with rocket fuel. The use of SPME resulted in high sensitivity, speed, small labor consumption due to an automation and simplicity of use. It was shown that water addition to soil leads to a significant decrease of recovery of almost all target transformation products of UDMH. The use of SPME for sampling and sample preparation resulted in detection of the total of 21 new compounds that are relevant to the UDMH transformation in soils. In addition, the number of confirmed transformation products of UDMH increased from 15 to 27. This sampling/sample preparation approach can be recommended for environmental assessment of soil samples from areas affected by space rocket activity
    The Effect of Preanalytical Factors on Stability of the Proteome and Selected Metabolites in Cerebrospinal Fluid (CSF)
    Rosenling, T. ; Slim, C.L. ; Christin, C. ; Coulier, L. ; Shi, S. ; Stoop, M.P. ; Bosman, J. ; Suits, F. ; Horvatovich, P.L. ; Stockhofe, N. ; Vreeken, R. ; Hankemeier, T. ; Gool, A.J. ; Luider, T.M. ; Bischoff, R. - \ 2009
    Journal of Proteome Research 8 (2009)12. - ISSN 1535-3893 - p. 5511 - 5522.
    chromatography-mass spectrometry - multiple-sclerosis - liquid-chromatography - biomarker discovery - cystatin-c - storage-conditions - sample collection - clinical-practice - lc-ms - serum
    To standardize the use of cerebrospinal fluid (CSF) for biomarker research, a set of stability studies have been performed on porcine samples to investigate the influence of common sample handling procedures on proteins, peptides, metabolites and free amino acids. This study focuses at the effect on proteins and peptides, analyzed by applying label-free quantitation using microfluidics nanoscale liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (chipLC-MS) as well as matrix-assisted laser desorption ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FT-ICR-MS) and Orbitrap LC-MS/MS to trypsin-digested CSF samples, The factors assessed were a 30 or 120 min time delay at room temperature before storage at -80 degrees C after the collection of CSF in order to mimic potential delays in the clinic (delayed storage), storage at 4 degrees C after trypsin digestion to mimic the time that samples remain in the cooled autosampler of the analyzer, and repeated freeze-thaw cycles to mimic storage and handling procedures in the laboratory. The delayed storage factor was also analyzed by gas chromatography mass spectrometry (GC-MS) and liquid chromatography mass spectrometry (LC-MS) for changes of metabolites and free amino acids, respectively. Our results show that repeated freeze/thawing introduced changes in transthyretin peptide levels. The trypsin digested samples left at 4 degrees C in the autosampler showed a time-dependent decrease of peak areas for peptides from prostaglandin D-synthase and serotransferrin. Delayed storage of CSF led to changes in prostaglandin D-synthase derived peptides as well as to increased levels of certain amino acids and metabolites. The changes of metabolites, amino acids and proteins in the delayed storage study appear to be related to remaining white blood cells. Our recommendations are to centrifuge CSF samples immediately after collection to remove white blood cells, aliquot, and then snap-freeze the supernatant in liquid nitrogen for storage at -80 degrees C. Preferably samples should not be left in the autosampler for more than 24 h and freeze/thaw cycles should be avoided if at all possible.
    Plant Micrometabolomics: The Analysis of Endogenous Metabolites Present in a Plant Cell or Tissue.
    Moco, S.I.A. ; Schneider, B. ; Vervoort, J.J.M. - \ 2009
    Journal of Proteome Research 8 (2009)4. - ISSN 1535-3893 - p. 1694 - 1703.
    nuclear-magnetic-resonance - chromatography-mass spectrometry - laser capture microdissection - solid-phase extraction - phenylphenalenone-related compounds - desorption electrospray-ionization - gene-expression analysis - cryogenic flow probe - single-cell - liqu
    Identification and quantification of metabolites occurring within specific cell types or single cells of plants and other organisms is of particular interest for natural product chemistry, chemical ecology, and biochemistry in general. The integration of studies at the gene, transcript, protein and metabolite levels in localized regions will provide useful information for the understanding of biology as a system. In this review, we summarize the latest developments in the analysis of metabolites present in small samples, micrometabolomics, dealing with sample preparation methods, with focus on laser-assisted microdissection, and the analytical technologies used. Mass spectrometry (MS) and nuclear magnetic resonance (NMR) are among the most emergent technologies in metabolomics, enabling the shortest route toward metabolite identification.
    Comparative LC-MS: A landscape of Peaks and Valleys
    America, A.H.P. ; Cordewener, J.H.G. - \ 2008
    Proteomics 8 (2008)4. - ISSN 1615-9853 - p. 731 - 749.
    chromatography-mass spectrometry - quantitative proteomic analysis - protein identification technology - missing value estimation - time tag strategy - liquid-chromatography - accurate mass - biomarker discovery - microarray data - breast-cancer
    Quantitative proteomics approaches using stable isotopes are well-known and used in many labs nowadays. More recently, high resolution quantitative approaches are reported that rely on LC-MS quantitation of peptide concentrations by comparing peak intensities between multiple runs obtained by continuous detection in MS mode. Characteristic of these comparative LC-MS procedures is that they do not rely on the use of stable isotopes; therefore the procedure is often referred to as label-free LC-MS. In order to compare at comprehensive scale peak intensity data in multiple LC-MS datasets, dedicated software is required for detection, matching and alignment of peaks. The high accuracy in quantitative determination of peptide abundancies provides an impressive level of detail. This approach also requires an experimental set-up where quantitative aspects of protein extraction and reproducible separation conditions need to be well controlled. In this paper we will provide insight in the critical parameters that affect the quality of the results and list an overview of the most recent software packages that are available for this procedure
    A novel approach for nontargeted data analysis for metabolomics : large-scale profiling of tomato fruit volatiles
    Tikunov, Y.M. ; Lommen, A. ; Vos, C.H. de; Verhoeven, H.A. ; Bino, R.J. ; Hall, R.D. ; Bovy, A.G. - \ 2005
    Plant Physiology 139 (2005)3. - ISSN 0032-0889 - p. 1125 - 1137.
    solid-phase microextraction - chromatography-mass spectrometry - plant functional genomics - gas-chromatography - methyl salicylate - flavor volatiles - chemometric analysis - rapid analysis - identification - organization
    To take full advantage of the power of functional genomics technologies and in particular those for metabolomics, both the analytical approach and the strategy chosen for data analysis need to be as unbiased and comprehensive as possible. Existing approaches to analyze metabolomic data still do not allow a fast and unbiased comparative analysis of the metabolic composition of the hundreds of genotypes that are often the target of modern investigations. We have now developed a novel strategy to analyze such metabolomic data. This approach consists of (1) full mass spectral alignment of gas chromatography (GC)-mass spectrometry (MS) metabolic profiles using the MetAlign software package, (2) followed by multivariate comparative analysis of metabolic phenotypes at the level of individual molecular fragments, and (3) multivariate mass spectral reconstruction, a method allowing metabolite discrimination, recognition, and identification. This approach has allowed a fast and unbiased comparative multivariate analysis of the volatile metabolite composition of ripe fruits of 94 tomato (Lycopersicon esculentum Mill.) genotypes, based on intensity patterns of >20,000 individual molecular fragments throughout 198 GC-MS datasets. Variation in metabolite composition, both between- and within-fruit types, was found and the discriminative metabolites were revealed. In the entire genotype set, a total of 322 different compounds could be distinguished using multivariate mass spectral reconstruction. A hierarchical cluster analysis of these metabolites resulted in clustering of structurally related metabolites derived from the same biochemical precursors. The approach chosen will further enhance the comprehensiveness of GC-MS-based metabolomics approaches and will therefore prove a useful addition to nontargeted functional genomics research
    An FTIR-DRIFT study on river sediment particle structure: Implications for biofilm dynamics and pollutant binding
    Galle, T. ; Lagen, B. van; Kurtenbach, A. ; Bierl, R. - \ 2004
    Environmental Science and Technology 38 (2004)17. - ISSN 0013-936X - p. 4496 - 4502.
    chromatography-mass spectrometry - particulate organic-matter - chemical-equilibrium model - humic substances - suspended sediment - blackwater river - macoma-balthica - humber rivers - fulvic-acids - waste-water
    Diffuse reflectance infrared Fourier transform (DRIFT) spectrometry was applied to a set of sediment samples collected by traps over one and a half years in a midmountainous river. Dynamic changes in hydrological and life-cycle conditions generated sediment particles of different Corg content and organic composition. Periods in the midst of or shortly after flood events left particles poor in Corg content with spectral features that were enriched in carboxylic and aromatic signals. These are characteristic of terrestrial oxidized vascular plant debris. Low-flow conditions saw the consequent build-up of amide, aliphatic, and polysaccharide moieties as expected for autochthonous biofilm derived material. A peak ratio of two bands representing the alternation of these two types of organic matter showed that flood particle Corg had a higher affinity for metals than the high Corg of mature biofilms, probably owing to higher COO- contents in the first. The relative dietary bioavailability of the metals from sediment Corg, which is related to the nutritional value of the substrate, is therefore probably lower in the aftermath of a flood than in prolonged low-flow situations. This needs to be accounted for in future metal speciation and bioavailability modeling approaches.
    Migration and sensory evaluation of irradiated polymers
    Stoffers, N.H. ; Linssen, J.P.H. ; Franz, R. ; Welle, F. - \ 2004
    Radiation Physics and Chemistry 71 (2004)1-2. - ISSN 0969-806X - p. 205 - 208.
    chromatography-mass spectrometry - volatile radiolysis products - plastics
    The effects on ionising irradiation on polymer additives, monomers and polymers themselves have been investigated. Changes of initial concentrations of certain additives and monomers, a change in their specific migration as well as sensory changes of the polymers were examined. Polymer stabilizers such as Irganox 1076 and Irgafos 168 used in polyethylene were found to be degraded by ionising radiation. Decreased concentrations of stabilisers in polyolefins led to lower specific migration, however, not to lower overall migration into food simulants. Irganox 1076 levels in polystyrene did not change up to irradiation doses of 54kGy. Sensory properties of LDPE, HDPE, PA6 and PA12 worsened, while sensory properties of PS improved with increasing irradiation doses.
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