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.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Improved forensic hair evidence for drugs of abuse by mass spectrometry
    Duvivier, W.F. - \ 2016
    Wageningen University. Promotor(en): Michel Nielen, co-promotor(en): Teris van Beek. - Wageningen : Wageningen University - ISBN 9789462578159 - 194
    forensic science - hair - analytical methods - spectrometry - forensische wetenschap - haar - analytische methoden - spectrometrie

    Forensic hair analysis can be used as alternative evidence next to body fluids, and to obtain retrospective timeline information of an individual’s drug exposure. Chapter 1 describes the general concepts of drug incorporation into hair, external contamination, and the current status and limitations of hair analysis methods are introduced. Furthermore, an overview of ambient ionization techniques is given, with emphasis on direct analysis in real time (DART).
    The instrumentation, ionization mechanisms, and application range of DART are presented. Scientific challenges and objectives to improve forensic hair evidence are formulated, which formed the basis of the research presented in this thesis.

    A major issue in forensic hair analysis is the possibility of false-positive results due to external contamination. In Chapter 2, an evidence-based evaluation of decontamination protocols for the removal of cannabinoid contamination is presented, mainly focused on
    Δ9-tetrahydrocannabinol (THC). Different solvents were extensively tested for their ability to remove cannabinoid contamination originating from cannabis smoke or indirect contact with cannabis plant material. After selection of the most efficient solvents, different sequential wash steps were tested on externally contaminated blank hair samples. Finally, application of the three best performing protocols on cannabis users’ hair, both as such and after deliberate contamination, resulted in removal of all contamination without removing incorporated THC. From the detailed scientific evidence reported in this chapter, a protocol using a single methanol wash followed by a single aqueous SDS solution is recommended to remove external cannabis contamination.

    A novel approach for the analysis of intact locks of hair consisting of DART combined with high resolution mass spectrometry (HRMS) is developed in Chapter 3. DART–HRMS settings were optimized for the analysis of THC and the accuracy of the probed hair zone was investigated using spiked blank hair samples. Intact locks of hair could be longitudinally scanned without the need of extensive sample preparation, resulting in analysis times of only minutes. Detection of THC was achieved in several hair samples from cannabis users. A quantitative liquid chromatography (LC)–MS/MS method was developed, in-house validated, and used to confirm the presence of THC in drug user hair samples. With a retrospective timeline accuracy of ±2 weeks, a significant improvement over conventional segmented hair analysis was achieved. Moreover, differentiation between zones of different THC content within a DART hair scan could be made, indicating possibilities for retrospective assessment of time of drug use.

    The DART hair scan method has been improved and expanded in Chapter 4. Targeted detection of four commonly used drugs of abuse (amphetamine, cocaine, MDMA and THC) with structural confirmation was achieved by data-dependent product ion scans. Simultaneously,
    full-scan high-resolution data was obtained and retrospectively interrogated versus a list of more than a hundred, less common, drugs of abuse and occasionally abused pharmaceutical drugs. The hair scan method was validated for the analysis of cocaine against an accredited LC–MS/MS method and the detection limit for cocaine was found to comply with the cut-off value of 0.5 ng/mg. Hair samples of 10 different drug users were analyzed. Next to detection of the four targeted drugs of abuse, retrospective data interrogation revealed several additional hits. The detected substances correlated well with reported drug use and by the detection of several metabolites, drug use could be unambiguously proven. The retrospective timeline accuracy was further improved by use of a high spatial resolution DART exit cone, which yielded a DART spot size corresponding to approximately 10 days of hair growth.

    When direct and/or ambient ionization techniques are used to analyze intact hair samples, endogenous isobaric ions can overlap with compounds of interest and yield
    false-positive results. The selectivity of four MS instruments with different mass analyzers (orbitrap, quadrupole orbitrap, triple quadrupole, time-of-flight) was evaluated in Chapter 5 by DART analysis of THC from hair samples. To avoid overlap of THC with isobaric ions originating from the hair matrix, a mass resolution of at least 30,000 FWHM was necessary. The use of travelling wave ion mobility spectrometry (TWIMS) resulted in increased selectivity by separation of isobaric ions based on their drift times. A triple quadrupole instrument in multiple reaction monitoring (MRM) mode was found to have the best sensitivity, however, the used transitions were not specific enough for use on drug user hair samples. Thus the selectivity needed to indisputably differentiate THC from endogenous isobaric ions in drug user hair samples could only be achieved by the high resolution of the tested orbitrap MS instruments.

    Chapter 6 demonstrates the application of forensic hair analysis techniques to veterinary control. Timeline information could be obtained from veterinary hair samples. For this purpose, a UPLC–MS/MS hair analysis method was adapted and optimized for smaller sample sizes.
    After validation of the method, segmented hair samples obtained from clenbuterol-treated calves using the forensic hair sampling protocol were analyzed and clenbuterol concentration profiles along the hair samples could be obtained. Assessment of the average growth rate of calf tail hair enabled retrospective determination of time of clenbuterol administration.
    The estimated time of administration was reproducible when analyzing sub-samples taken from the same lock of hair and duplicate locks of hair, and in good correlation with the actual treatment.

    Through the research presented in this thesis, novel approaches in hair analysis have been developed and the value of forensic hair evidence improved considerably. In Chapter 7, the main achievements of this thesis are discussed in detail and an insight in the future perspectives of hair analysis and ambient ionization is given. Potential further applications of the DART hair scan method, and ambient ionization in general, are presented, including some preliminary results of new decontamination strategies, hair analysis possibilities, and other forensic uses of DART ionization.

    Space-born spectrodirectional estimation of forest properties
    Verrelst, J. - \ 2010
    Wageningen University. Promotor(en): Michael Schaepman, co-promotor(en): Jan Clevers; B. Koetz. - [S.l. : S.n. - ISBN 9789085856214 - 152
    bossen - bosecologie - achteruitgang, bossen - gezondheidstoestand van het bos - bosinventarisaties - remote sensing - spectrometrie - bosbedrijfsvoering - bosmonitoring - bosstructuur - nabij infrarood spectroscopie - geïntegreerd bosbeheer - forests - forest ecology - forest decline - forest health - forest inventories - remote sensing - spectrometry - forest management - forest monitoring - forest structure - near infrared spectroscopy - integrated forest management
    With the upcoming global warming forests are under threat. To forecast climate change impacts and adaptations, there is need for developing improved forest monitoring services, which are able to record, quantify and map bio-indicators of the forests’ health status across the globe. In this context, Earth observation (EO) can provide a substantial amount of up-to-date information about the biochemical and structural conditions of our forests at a local-to-global scale. Among the optical EO instruments in space, one of the most innovative instruments is the experimental Compact High Resolution Imaging Spectrometer (CHRIS) on board the PROBA-1 (Project for On Board Autonomy) satellite. CHRIS is capable of sampling reflected radiation at five viewing angles over the visible and near-infrared (VNIR) region of the solar spectrum with a relatively high spatial resolution (~17 m). The as such acquired spectrodirectional (combined multi-angular and spectroscopy) data may lead to new opportunities for space-based forest monitoring applications, yet the added value of canopy reflectance anisotropy measured over the whole VNIR spectral region is largely unknown. This is why the use of space-borne spectrodirectional data of a forested target has been investigated in this thesis.
    Detectie van Phytophthora infestans in geïnfecteerd pootgoed door luchtanalyse
    Jansen, R.M.C. ; Hofstee, J.W. - \ 2007
    aardappelen - pootaardappelen - phytophthora infestans - ziektebestrijding - methodologie - gaschromatografie - spectrometrie - analytische methoden - potatoes - seed potatoes - phytophthora infestans - disease control - methodology - gas chromatography - spectrometry - analytical methods
    Onderzoek met traditionele gaschromatografie gekoppeld aan massaspectrometrie (GC-MS) voor identificatie van geurstoffen afkomstig van kunstmatig geïnfecteerd pootgoed en een evaluatie Biosensor set-up op basis van insectantenne
    High Tech Kleurensorteerder voor Zaden : Een nieuwe technologie voor opwaardering van zaadpartijen
    Jalink, H. ; Schoor, R. van der - \ 2006
    fusarium - tarwe - zaadproductie - zaadkwaliteit - sorteren - kwalitatieve technieken - spectrometrie - fusarium - wheat - seed production - seed quality - sorting - qualitative techniques - spectrometry
    Een nieuwe methode voor sorteren van tarwezaad op besmetting met Fusarium is ontwikkeld. De methode is gebaseerd op het nauwkeurig meten van kleurverschillen van het zaad, zowel verschillen in het zichtbare als ook in het nabij infrarood gebied.
    Microspectroscopie: een unieke kijk op de nanowereld van de levende cel
    Visser, A.J.W.G. - \ 2005
    Wageningen : Wageningen Universiteit - 39
    celbiologie - celstructuur - spectrometrie - nanotechnologie - cellular biology - cell structure - spectrometry - nanotechnology
    Plant analysis: procedures
    Temminghoff, E.J.M. ; Houba, V.J.G. - \ 2004
    Dordrecht : Kluwer Academic Publishers - ISBN 9781402027697 - 179
    planten - plantensamenstelling - chemische samenstelling - technieken - spectrometrie - handboeken - plants - plant composition - chemical composition - techniques - spectrometry - handbooks
    Veldspectrometer voor Centrum Geo-Informatie (WUR)
    Bartholomeus, H. ; Schaepman, M.E. - \ 2004
    Agro Informatica 17 (2004)1. - ISSN 0925-4455 - p. 21 - 24.
    spectrometers - spectrometrie - reflectie - remote sensing - monitoring - veldwerk - spectrometers - spectrometry - reflection - monitoring - remote sensing - field work
    Eind 2003 is door de leerstoelgroep Geo-Informatie en Remote Sensing van Wageningen UR een veldspectrometer (ASD Fieldspec Pro FR) aangeschaft. Naar aanleiding hiervan wordt ingegaan op wat een veldspectrometer meet, hoe die gebruikt wordt, en wat de praktische toepassingen zijn. Dit aan de hand van 3 projecten
    Early detection of drought stress in grass swards with imaging spectroscopy
    Schut, A.G.T. ; Ketelaars, J.J.M.H. - \ 2003
    NJAS Wageningen Journal of Life Sciences 51 (2003)3. - ISSN 1573-5214 - p. 319 - 337.
    grasveld - lolium perenne - droogte - stress - spectroscopie - spectrometrie - reflectiefactor - grass sward - lolium perenne - drought - stress - spectroscopy - spectrometry - reflectance - grown perennial ryegrass - leaf water status - spectral reflectance - red edge - leaves - vegetation - cotton
    The potential of an experimental imaging spectroscopy system with high spatial (0.28-1.45 mm2) and spectral (5-13 nm) resolution was explored for early detection of drought stress in grass. A climate chamber experiment was conducted with nine Lolium perenne L. mini swards with drought stress treatments at two nitrogen levels. Images were recorded once every two days. Growth was monitored by changes in ground cover (GC), index of reflection intensity (IRI) and wavelength position of and gradient at inflection points, as estimated from images. Drought stress increased leaf dry matter and sugar content. Drought stress decelerated and ultimately reversed GC evolution, and kept IRI at low values. In contrast to unstressed growth, all absorption features narrowed and became shallower under drought stress. The inflection points near 1390 and 1500 nm were most sensitive to drought stress. Differences between drought stress and control swards were detected shortly before leaf water content dropped below 80%. The evolution of inflection point wavelength positions reversed under drought stress, except for the inflection point at the red edge where the shift to longer wavelengths during growth accelerated. The relation between inflection points at 705 and 1390 nm differentiated unstressed swards at an early growth stage from drought-stressed swards in a later growth stage
    Imaging spectroscopy for characterisation of grass swards
    Schut, A.G.T. - \ 2003
    Wageningen University. Promotor(en): J. Goudriaan, co-promotor(en): Jan Ketelaars. - [S.I.] : S.n. - ISBN 9789058088376 - 264
    grasveld - graslanden - spectroscopie - spectrometrie - remote sensing - reflectie - reflectiefactor - detectie - groei - stress - lolium perenne - trifolium repens - graslandbeheer - lolium perenne - trifolium repens - grass sward - grasslands - grassland management - spectroscopy - spectrometry - remote sensing - reflection - reflectance - detection - growth - stress

    Keywords: Imaging spectroscopy, imaging spectrometry, remote sensing, reflection, reflectance, grass sward, white clover, recognition, characterisation, ground cover, growth monitoring, stress detection, heterogeneity quantification

    The potential of imaging spectroscopy as a tool for characterisation of grass swards was explored with respect to growth monitoring, detection of nitrogen and drought stress, and assessment of dry matter yield, clover content, nutrient content, feeding value, sward heterogeneity and production capacity. To this end, an experimental imaging spectroscopy system was developed. The system detects reflection in image lines in the wavelength range from 405-1659 nm with three different sensors at 1.3 m above the soil surface. Spectral resolution varies between 5-13 nm, and spatial resolution between 0.28-1.45 mm 2per pixel at the soil. As a result of system design, reflection intensity is a function of leaf height and leaf angle. The system was tested on mini swards grown in containers. For each mini sward, 42 image lines were recorded in a regular sampling pattern per recording event.

    Five experiments were conducted with Lolium perenne L. and/or Trifolium repens L. mini swards. In these experiments degree of sward damage, level of nitrogen (N) application (two experiments), water supply and white clover content were varied. In the sward damage experiment and in one N experiment light interception was recorded regularly; at harvest, also crop height and canopy reflectance (with a Cropscan) was measured. Mini swards were harvested at a fixed level and in one of the N experiments in three strata. During the experiments, hyperspectral reflectance was recorded 2-4 times per week.

    Image lines were classified to separate pixels containing soil, dead material and green leaves. These classes were subdivided into reflection intensity classes. Ground cover (GC), reflection intensity, image line texture, spatial heterogeneity and patterns, and spectral characteristics of green leaves were quantified. An index of reflection intensity (IRI) measured the distribution of green pixels over intensity classes and quantified vertical canopy geometry. Horizontal sward heterogeneity was quantified with the spatial standard deviation of GC (GC-SSD) and logarithmically transformed GC (TGC-SSD), and image line texture and spatial patterns with wavelet entropy (WE). Spectral characteristics were quantified with shifts of various spectral edges. Partial least squares (PLS) models combining spectral and spatial information were calibrated and validated on two separate data-sets from the sward damage and one N experiment, in order to predict dry matter (DM) yield, feeding quality and nutrient content. Effects of replicate observations on reduction of prediction error were studied for different fractions of model bias.

    GC was differently related to light interception under a cloudy sky and under a clear sky (R 2adj = 0.87-0.94) and also for dense and open swards. Growth was accurately monitored with evolution of GC and IRI, and GC and IRI at harvest were strongly related to DM yield (R 2adj = 0.75-0.82). Seasonal means of GC and IRI were strongly (R 2adj = 0.77-0.93) related to annual DM matter yield and light interception capacity. There was a clear (R 2adj = 0.69) relation between seasonal mean GC-SSD and tiller density. Seasonal means of GC-SSD differentiated dense from damaged swards. The WE of image line texture robustly differentiated clover from grass swards, while mixtures had intermediate values. Position of spectral edges was strongly related to reflection intensity. This relation differed for grass and clover swards, varied with N supply level and changed after harvesting canopy strata. Leaf angle was identified as the most important factor affecting this relationship. Drought stress was detected in an early stage, when DM content of leaves was still below 20%, from shifts of edges near water absorption features. A combination of shifts of the green and red edge was strongly related (R 2=0.95) to DM yield reduction due to N shortage. The prediction errors relative to the mean (of validation sets) of the PLS models were 6.2-11.7 % for N content, 5.5-9.1 % for DM content, 13.6-18.7 % for sugar content, 6.0-7.5 % for ash content, and 3.5-4.8 % for crude fibre content. Predictions of P, K, S, Mg, Na and Fe were robust in both experiments. Combining GC and IRI with mean sward spectra resulted in a prediction error of 235-268 kg DM ha -1for yields of less than 1000 up to 4000 kg DM ha -1. Multiple observations may reduce the mean prediction error for DM yield with 27 to 54%, depending on model bias and number of observations. The accuracy of DM yield assessment with imaging spectroscopy was better than with the disk plate meter or Cropscan. It is concluded that imaging spectroscopy is a powerful tool in grassland research and may provide valuable information for fine-tuning of grassland management. In this study it provided fast, automatic and non-destructive means for monitoring and quantification of growth, and estimating dry matter yield, spatial heterogeneity and sward damage, nitrogen and water deficiency, clover content, feeding quality and nutrient content of swards. Finally, system requirements for application of imaging spectroscopy in the field are discussed.

    Spectrometrische bepaling van het gehalte van weieiwit in melkpoeders
    Baltussen, M.A.H. - \ 2002
    Wageningen : RIKILT (Rapport / RIKILT 2002.008) - 15
    melkpoeder - wei-eiwit - spectrometrie - dried milk - whey protein - spectrometry
    Verslag XXVII Colloquium Spectroscopicum Internationale : 9 - 14 juni 1991, Bergen, Noorwegen
    Ruig, W.G. de - \ 1991
    Wageningen : DLO-Rijks-Kwaliteitsinstituut voor Land- en Tuinbouwprodukten (Rapport / RIKILT-DLO 91.33) - 15
    spectrometrie - spectroscopie - kernmagnetische resonantie - residuen - chemometrie - spectrometry - spectroscopy - nuclear magnetic resonance - residues - chemometrics
    Het Colloquium Spectroscopicum Internationale is een tweejaarlijks congres, gewijd aan spectroscopische technieken, zowel atomaire als moleculaire spectrometrie. Dit rapport geeft een verslag van het 27e congres, dat in juni 1991 in Bergen (Noorwegen) werd gehouden.
    Bepaling van decoquinaat volgens EEG doc. VI/3205/79
    Beek, W.M.J. ; Buizer, F.G. ; Hollman, P. - \ 1982
    Wageningen : RIKILT (Verslag / RIKILT 82.19) - 2
    decoquinaat - mengvoer - spectrometrie - fluorescentie - chemische analyse - decoquinate - compound feeds - spectrometry - fluorescence - chemical analysis
    Decoquinaat werd onderzocht met behulp van de EEG methode in drie monsters, welke verstrekt werden door het Laboratoire Interregional, Rennes. De recovery van de bepaling werd ook onderzocht.
    Perchlorering van PCB-extracten van paling : verificatie van Decachloorbifenyl m.b.v. massa spectrometrie
    Traag, W.A. ; Mazijk, R.J. van; Tuinstra, L.G.M.Th. - \ 1980
    Wageningen : RIKILT (Verslag / RIKILT 80.25) - 2
    perchloraten - anguilla - massaspectrometrie - spectrometrie - besmetters - polychloorbifenylen - perchlorates - anguilla - mass spectrometry - spectrometry - contaminants - polychlorinated biphenyls
    De gaschromatografische analyse van Decachloorbifenyl (DCB) wordt meestal uitgevoerd op een korte gepakte kolom, waardoor het mogelijk is een groot aantal monsters in een kort tijdsbestek te analyseren. Om eventuele interferentie aan te tonen werd de analyse uitgevoerd op een capillaire kolom met hoog scheidend vermogen. Bij de E.C.-detectie bleek dat na de DCB piek nog één component elueerde welke bij gebruik van gepakte "korte" kolommen samenvalt met DCB. Bij de MS-detectie bleek dat deze na DCB eluerende component geen electroninvangende atomen bezit waardoor deze component bij de EC-detectie vele malen ongevoeliger is dan DCB zelf. Uit het onderzoek kunnen de drie volgende punten worden geconcludeerd: 1) bij de DCB-bepaling treedt er bij gebruik van korte gepakte kolommen interferentie op. 2) De mate van deze interferentie zal afhankelijk zijn van de matrix 3) De verkregen DCB-gehalten en de daaruit berekende PCB-gehalten zullen te hoog zijn.
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