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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    Future water quality monitoring - Adapting tools to deal with mixtures of pollutants in water resource management
    Altenburger, R. ; Ait-Aissa, S. ; Antczak, P. ; Backhaus, T. ; Barcelo, D. ; Seiler, T. ; Brion, F. ; Focks, A. - \ 2015
    Science of the Total Environment 512-513 (2015). - ISSN 0048-9697 - p. 540 - 551.
    effect-directed analysis - environmental risk-assessment - tandem mass-spectrometry - community tolerance pict - waste-water - estrogenic compounds - surface waters - conceptual-framework - organic-chemicals - zebrafish embryos
    Environmental quality monitoring of water resources is challenged with providing the basis for safeguarding the environment against adverse biological effects of anthropogenic chemical contamination from diffuse and point sources. While current regulatory efforts focus on monitoring and assessing a few legacy chemicals, many more anthropogenic chemicals can be detected simultaneously in our aquatic resources. However, exposure to chemical mixtures does not necessarily translate into adverse biological effects nor clearly shows whether mitigation measures are needed. Thus, the question which mixtures are present and which have associated combined effects becomes central for defining adequate monitoring and assessment strategies. Here we describe the vision of the international, EU-funded project SOLUTIONS, where three routes are explored to link the occurrence of chemical mixtures at specific sites to the assessment of adverse biological combination effects. First of all, multi-residue target and non-target screening techniques covering a broader range of anticipated chemicals co-occurring in the environment are being developed. By improving sensitivity and detection limits for known bioactive compounds of concern, new analytical chemistry data for multiple components can be obtained and used to characterise priority mixtures. This information on chemical occurrence will be used to predict mixture toxicity and to derive combined effect estimates suitable for advancing environmental quality standards. Secondly, bioanalytical tools will be explored to provide aggregate bioactivity measures integrating all components that produce common (adverse) outcomes even for mixtures of varying compositions. The ambition is to provide comprehensive arrays of effect-based tools and trait-based field observations that link multiple chemical exposures to various environmental protection goals more directly and to provide improved in situ observations for impact assessment of mixtures. Thirdly, effect-directed analysis (EDA) will be applied to identify major drivers of mixture toxicity. Refinements of EDA include the use of statistical approaches with monitoring information for guidance of experimental EDA studies. These three approaches will be explored using case studies at the Danube and Rhine river basins as well as rivers of the Iberian Peninsula. The synthesis of findings will be organised to provide guidance for future solution-oriented environmental monitoring and explore more systematic ways to assess mixture exposures and combination effects in future water quality monitoring.
    Ultratrace LC-MS/MS Analysis of Segmented Calf Hair for Retrospective Assessment of Time of Clenbuterol Administration in Agriforensics
    Duvivier, W.F. ; Beek, T.A. van; Meijer, T. ; Peeters, R.J.P. ; Groot, M.J. ; Sterk, S.S. ; Nielen, M.W.F. - \ 2015
    Journal of Agricultural and Food Chemistry 63 (2015)2. - ISSN 0021-8561 - p. 493 - 499.
    tandem mass-spectrometry - performance liquid-chromatography - beta-agonist residues - equine hair - bovine hair - human urine - cattle - calves - contamination - samples
    In agriforensics, time of administration is often debated when illegal drug residues, such as clenbuterol, are found in frequently traded cattle. In this proof-of-concept work, the feasibility of obtaining retrospective timeline information from segmented calf tail hair analyses has been studied. First, an ultraperformance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS) hair analysis method was adapted to accommodate smaller sample sizes and in-house validated. Then, longitudinal 1 cm segments of calf tail hair were analyzed to obtain clenbuterol concentration profiles. The profiles found were in good agreement with calculated, theoretical positions of the clenbuterol residues along the hair. Following assessment of the average growth rate of calf tail hair, time of clenbuterol administration could be retrospectively determined from segmented hair analysis data. The data from the initial animal treatment study (n = 2) suggest that time of treatment can be retrospectively estimated with an error of 3–17 days.
    Evaluation of the Discriminative Potential of a Novel Biomarker for Estradiol Treatments in Bovine Animals
    Regal, P. ; Blokland, M.H. ; Fente, C.A. ; Sterk, S.S. ; Cepeda, A. ; Ginkel, L.A. van - \ 2015
    Journal of Agricultural and Food Chemistry 63 (2015)1. - ISSN 0021-8561 - p. 370 - 378.
    tandem mass-spectrometry - timed artificial-insemination - beef-cattle - protein biomarkers - gene-expression - hormone abuse - plasma - 17-beta-estradiol - estrogen - detect
    The endogenous occurrence of natural hormones obstructs the application of classical targeted methods as confirmatory options. In the case of estradiol, the ultimate confirmation of its exogenous administration relies on gas chromatography coupled to combustion/isotope ratio mass spectrometry (GC-C/IRMS). A serum dipeptide composed of pyroglutamic acid and phenylalanine was identified as a potential biomarker of estradiol treatments in adult cows. To evaluate its potential to pinpoint suspicious samples, samples from prepubertal females under different estrogenic treatments have been analyzed. The results confirmed the up-regulation of the dipeptide in adult bovines. The 2-week-old females exhibited short-lasting responses only in a few animals. The 6-month-old female showed a delayed but clear increase on the biomarker level. The composition of the anabolic preparations, the dose, and/or the administration route are possible additional reasons for the reduced response in young animals. A comparison to previous results reported by various researchers is included.
    Presence of the neurotoxin BMAA in aquatic ecosystems: What do we really know?
    Faassen, E.J. - \ 2014
    Toxins 6 (2014)3. - ISSN 2072-6651 - p. 1109 - 1138.
    methylamino-l-alanine - amyotrophic-lateral-sclerosis - performance liquid-chromatography - tandem mass-spectrometry - solid-phase extraction - amino-acid bmaa - cyanobacterial neurotoxin - neurodegenerative disease - 2,4-diaminobutyric acid - environmental-sample
    The neurotoxin ß-N-methylamino-L-alanine (BMAA) is suspected to play a role in the neurological diseases amyotrophic lateral sclerosis, Alzheimer's disease, and Parkinson's disease. BMAA production by cyanobacteria has been reported and contact with cyanobacteria infested waters or consumption of aquatic organisms are possible pathways to human exposure. However, there is little consensus regarding whether BMAA is present in cyanobacteria or not, and if so, at what concentrations. The aim of this review is to indicate the current state of knowledge on the presence of BMAA in aquatic ecosystems. Some studies have convincingly shown that BMAA can be present in aquatic samples at the µg/g dry weight level, which is around the detection limit of some equally credible studies in which no BMAA was detected. However, for the majority of the reviewed articles, it was unclear whether BMAA was correctly identified, either because inadequate analytical methods were used, or because poor reporting of analyses made it impossible to verify the results. Poor analysis, reporting and prolific errors have shaken the foundations of BMAA research. First steps towards estimation of human BMAA exposure are to develop and use selective, inter-laboratory validated methods and to correctly report the analytical work.
    Quantitative modelling to estimate the transfer of pharmaceuticals through the food production system
    Chitescu, C.L. ; Nicolau, A.I. ; Romkens, P.F.A.M. ; Fels-Klerx, H.J. van der - \ 2014
    Journal of Environmental Science and Health. Part B, Pesticides Food Contaminants, and agricultural wastes 49 (2014)7. - ISSN 0360-1234 - p. 457 - 467.
    tandem mass-spectrometry - veterinary antibiotics - terrestrial environment - tetracycline residues - liquid-chromatography - organic contaminants - degradation kinetics - exposure assessment - poultry litter - animal manure
    Use of pharmaceuticals in animal production may cause an indirect route of contamination of food products of animal origin. This study aimed to assess, through mathematical modelling, the transfer of pharmaceuticals from contaminated soil, through plant uptake, into the dairy food production chain. The scenarios, model parameters, and values refer to contaminants in emission slurry production, storage time, immission into soil, plant uptake, bioaccumulation in the animal's body, and transfer to meat and milk. Modelling results confirm the possibility of contamination of dairy cow's meat and milk due the ingestion of contaminated feed by the cattle. The estimated concentration of pharmaceutical residues obtained for meat ranged from 0 to 6 ng kg-1 for oxytetracycline, from 0.011 to 0.181 µg kg-1 for sulfamethoxazole, and from 4.70 to 11.86 µg kg-1 for ketoconazole. The estimated concentrations for milk were: zero for oxytetracycline, lower than 40 ng L-1 for sulfamethoxazole, and from 0.98 to 2.48 µg L-1 for ketoconazole. Results obtained for the three selected pharmaceuticals indicate a minor risk for human health. This study showed that supply chain modelling could be an effective tool in assessing the indirect contamination of feedstuff and animal products by residues of pharmaceuticals. The model can easily be adjusted to other contaminants and supply chain and, in this way, present a valuable tool to underpin decision making.
    Quantitative label-free phosphoproteomics of six different life stages of the late blight pathogen Phytophthora infestans reveals abundant phosphorylation of members of the CRN effector family
    Resjö, S. ; Ali, A. ; Meijer, H.J.G. ; Seidl, M.F. ; Snel, B. ; Sandin, M. ; Levander, F. ; Govers, F. ; Andreasson, E. - \ 2014
    Journal of Proteome Research 13 (2014)4. - ISSN 1535-3893 - p. 1848 - 1859.
    tandem mass-spectrometry - protein-kinases - arabidopsis-thaliana - in-vitro - proteomics - identification - expression - potato - organization - specificity
    The oomycete Phytophthora infestans is the causal agent of late blight in potato and tomato. Since the underlying processes that govern pathogenicity and development in P. infestans are largely unknown, we have performed a large-scale phosphoproteomics study of six different P. infestans life stages. We have obtained quantitative data for 2922 phosphopeptides and compared their abundance. Life-stage-specific phosphopeptides include ATP-binding cassette transporters and a kinase that only occurs in appressoria. In an extended data set, we identified 2179 phosphorylation sites and deduced 22 phosphomotifs. Several of the phosphomotifs matched consensus sequences of kinases that occur in P. infestans but not Arabidopsis. In addition, we detected tyrosine phosphopeptides that are potential targets of kinases resembling mammalian tyrosine kinases. Among the phosphorylated proteins are members of the RXLR and Crinkler effector families. The latter are phosphorylated in several life stages and at multiple positions, in sites that are conserved between different members of the Crinkler family. This indicates that proteins in the Crinkler family have functions beyond their putative role as (necrosis-inducing) effectors. This phosphoproteomics data will be instrumental for studies on oomycetes and host–oomycete interactions. The data sets have been deposited to ProteomeXchange (identifier PXD000433).
    Determination of nivalenol in food and feed: an update
    Malachova, A. ; Egmond, H.P. van; Berthiller, F. ; Krska, R. - \ 2014
    World Mycotoxin Journal 7 (2014)3. - ISSN 1875-0710 - p. 247 - 255.
    tandem mass-spectrometry - b trichothecene mycotoxins - lc-ms/ms method - electrochemical detection - fusarium mycotoxins - multiple mycotoxins - quechers procedure - masked mycotoxins - cereal products - maize silage
    Based on the recent scientific opinion published by the EFSA CONTAM panel on the risks to human and animal health related to the presence of nivalenol in food and feed, this article provides an update on the determination of this Fusarium mycotoxin. After a brief introduction into the chemistry of nivalenol, chromatographic methods as well as other approaches are being discussed. Methods for the determination of nivalenol are well established and can be applied for the analysis of cereals, food, feed and biological samples. Accurate quantification of nivalenol is mostly carried out by liquid chromatography coupled with (multi-stage) mass spectrometry (MS) often within a multi-analyte approach. Some novel techniques, such as direct analysis in real time (DART) MS and electrochemical methods, have shown potential to determine nivalenol, but applications for routine measurements are not yet available. None of the currently available analytical methods has been formally validated in interlaboratory validation studies. While a certified calibrant for nivalenol is available, no matrix reference materials have been developed. Due to the scarcity of appropriate antibodies also no rapid immunochemical methods specific for nivalenol have become available
    Determination of T-2 and HT-2 toxins in food and feed: an update
    Krska, R. ; Malachova, A. ; Berthiller, F. ; Egmond, H.P. van - \ 2014
    World Mycotoxin Journal 7 (2014)2. - ISSN 1875-0710 - p. 131 - 142.
    tandem mass-spectrometry - performance liquid-chromatography - fusarium mycotoxin content - in-house validation - lc-ms/ms method - a trichothecenes - immunoaffinity cleanup - fluorescence detection - gas-chromatography - masked mycotoxins
    Based on the recent scientific opinion of the European Food Safety Authority (EFSA) Panel on Contaminants in the Food Chain on the risks to human and animal health related to the presence of T-2 and HT-2 toxins in food and feed that was published by EFSA in the EFSA Journal, this article provides an update on the determination of these Fusarium mycotoxins. After a brief introduction into the chemistry of these toxins, both chromatographic and immuno-analytical methods are discussed for the determination of these type A trichothecenes. During the last decade, liquid chromatography with (tandem) mass spectrometry has become the most frequently used method for the determination of T-2 and HT-2 toxins, often within a multi-analyte approach. However, complex matrices and the resulting signal suppression effects, as observed particularly in electrospray-mass spectrometry methods owing to matrix effects, may require careful optimisation of clean-up, usage of matrix matched standards, or e.g. the use of internal standards. For specific purposes where extremely low limits of quantification are needed, e.g. for the analysis of duplicate diets, a dedicated gas chromatography method with multistage mass spectrometry has become available. Other novel analytical approaches to determine T-2 and HT-2 toxins in food and feed include biosensor-based methods in surface plasmon resonance and electrochemical formats, as well as DNA microchip assays. For rapid screening, several immunochemical methods (mostly ELISAs) have become available and some are sold as commercial test kits. Whereas these methods work fast, cross-reactivities with other trichothecenes can have an undesired effect on their accuracy. While proficiency tests including T-2 and HT-2 toxins have been carried out, none of the chromatographic or immunochemical methods have been formally validated in interlaboratory validation studies. There are no certified reference materials available for T-2 and HT-2 toxins.
    Analysis of pesticide residues in strawberries and soils by GC-MS/MS, LC-MS/MS and two-dimensional GC– time-of-flight MS comparing organic and integrated pest management farming
    Fernandes, V.C. ; Lehotay, S.J. ; Geis-Asteggiantec, L. ; Kwon, H. ; Mol, J.G.J. ; Kamp, H.J. van der; Mateus, N. ; Domingues, V.F. ; Delerue-Matos, C. - \ 2014
    Food Additives & Contaminants. Pt. A, Chemistry, Analysis, Control, Exposure & Risk Assessment 31 (2014)2. - ISSN 1944-0049 - p. 262 - 270.
    pressure gas-chromatography - tandem mass-spectrometry - performance liquid-chromatography - quechers sample preparation - qualitative aspects - multiresidue method - vegetables - fruits - extraction - foods
    In this study, we analyzed 22 strawberry and soil samples after their collection over the course of 2 years to compare the residue profiles from organic farming to integrated pest management practices in Portugal. For sample preparation, we used the citrate-buffered version of the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method. We applied three different methods for analysis: (i) 27 pesticides were targeted using LC-MS/MS; (ii) 143 were targeted using low pressure GC - tandem mass spectrometry (LP-GC-MS/MS); and (iii) More than > 600 pesticides were screened in a targeted and untargeted approach using comprehensive, two-dimensional gas chromatography time-of-flight mass spectrometry (GC × GC-TOF-MS). Comparison was made of the analyses using the different methods for the shared samples. The results were similar, thereby providing satisfactory confirmation of both similarly positive and negative findings. No pesticides were found in the organic-farmed samples. In samples from integrated pest management practices, 9 pesticides were determined and confirmed to be present ranging from 2 µg kg-1 for fluazifop-p-butyl to 50 µg kg-1 for fenpropathrin. Concentrations of residues in strawberries were less than European maximum residue limits.
    Metaproteomics of our microbiome - Developing insight in function and activity in man and model systems
    Kolmeder, C. ; Vos, W.M. de - \ 2014
    Journal of Proteomics 97 (2014). - ISSN 1874-3919 - p. 3 - 16.
    3-dimensional peptide fractionation - gastrointestinal-tract microbiota - tandem mass-spectrometry - human gut microbiome - in-vitro model - escherichia-coli - environmental proteomics - intestinal microbiota - community structure - effective recovery
    We are all colonized by a large microbiome, a complex set of microbes that have intimate associations with us. Culture-based approaches have provided insights in the complexity of the microbial communities living on surfaces inside and outside the body. However, the application of high-throughput sequencing technologies has identified large numbers of community members at both the phylogenetic and the (meta-)genome level. The latter allowed defining a reference set of several millions of mainly bacterial genes and provided the basis for developing approaches to target the activity and function of the human microbiome with proteomic techniques. Moreover, recent improvements in protein and peptide separation efficiencies and highly accurate mass spectrometers have promoted the field of metaproteomics, the study of the collective proteome of microbial communities. We here review the approaches that have been developed to study the human metaproteomes, focusing on intestinal tract and body fluids. Moreover, we complement these by considering metaproteomic studies in mouse and other model systems offering the option to study single species or simple consortia. Finally, we discuss present and future avenues that may be used to advance the application of metaproteomic approaches to further improve our understanding of the microbes inside and around our body. This article is part of a Special Issue entitled: Trends in Microbial Proteomics
    Secondary Metabolites of Capsicum Species and Their Importance in the Human Diet
    Wahyuni, Y. ; Ballester, A.R. ; Sudarmonowati, E. ; Bino, R.J. ; Bovy, A.G. - \ 2013
    Journal of Natural Products 76 (2013)4. - ISSN 0163-3864 - p. 783 - 793.
    chlorophyll catabolism pathway - capsaicinoid-like substances - tandem mass-spectrometry - red-pepper paprika - mature fruit color - annuum-l cultivars - cv ch-19 sweet - antioxidant activity - candidate gene - ascorbic-acid
    The genus Capsicum (pepper) comprises a large number of wild and cultivated species. The plants are grown all over the world, primarily in tropical and subtropical countries. The fruits are an excellent source of health-related compounds, such as ascorbic acid (vitamin C), carotenoids (provitamin A), to copherols (vitamin E), flavonoids, and capsaicinoids. Pepper fruits have been used for fresh and cooked consumption, as well as for medicinal purposes, such as treatment of asthma, coughs, sore throats, and toothache. Depending on its uses, there are several main characters important for product quality; pungency, bright attractive colors, highly concentrated extracts, and a small number of seeds are the main characters on which quality is based and priced. Herein, a general overview of biochemical composition, medical properties of these compounds, and characteristics of quality attributes of pepper fruits is presented.
    The disposition of oxytetracycline to feathers after poultry treatment
    Berendsen, B.J.A. ; Bor, G. ; Gerritsen, H.W. ; Jansen, L.J.M. ; Zuidema, T. - \ 2013
    Food Additives & Contaminants. Pt. A, Chemistry, Analysis, Control, Exposure & Risk Assessment 30 (2013)12. - ISSN 1944-0049 - p. 2102 - 2107.
    tandem mass-spectrometry - growth-promoting agents - residue analysis - veterinary drugs - bovine - feed
    In the combat against bacterial resistance, there is a clear need to check the use of antibiotics in animal husbandry, including poultry breeding. The use of chicken feathers as a tool for the detection of use of antibiotics was investigated. An extraction method for the analysis of oxytetracycline (OTC) from feathers was developed and was tested by using incurred feathers obtained from a controlled animal treatment study. The use of McIlvain-ethylenediaminetetraacetic acid buffer only in combination with acetone gave the highest extraction yield, indicating the need of an organic solvent for feather extraction. By using the developed method, it was found that after a withdrawal time, the OTC concentration in feathers is in the mg kg(-1) range, far higher than that in muscle and liver tissue. Based on the analysis of individual segments of feathers from OTC-treated chicken, evidence was found supporting the hypothesis of secretion of antibiotics through the uropygial gland and external spread over feathers by grooming behaviour. It was also found that part of the administered OTC is built into the feather rachis. Finally, we provide the first evidence that the analysis of individual segments of the rachis can be used as a tool to discriminate among different treatment strategies, for example, therapeutic versus subtherapeutic. As a result, we concluded that the analysis of feathers is an extremely valuable tool in residue analysis of antibiotics.
    A toolkit for the mzIdentML standard: the ProteoIDViewer, the mzidLibrary and the mzidValidator.
    Ghali, F. ; Krishna, R. ; Lukasse, P.N.J. ; Martínez-Bartolomé, S. ; Reisinger, F. ; Hermjakob, H. ; Vizcaíno, J.A. ; Jones, A.R. - \ 2013
    Molecular and Cellular Proteomics 12 (2013). - ISSN 1535-9476 - p. 3026 - 3035.
    tandem mass-spectrometry - proteomics - software - parser - miape - rates
    The Proteomics Standards Initiative has recently released the mzIdentML data standard for representing peptide and protein identification results, for example, created by a search engine. When a new standard format is produced, it is important that software tools are available that make it straightforward for laboratory scientists to use it routinely and for bioinformaticians to embed support in their own tools. Here we report the release of several open-source Java-based software packages based on mzIdentML: ProteoIDViewer, mzidLibrary, and mzidValidator. The ProteoIDViewer is a desktop application allowing users to visualize mzIdentML-formatted results originating from any appropriate identification software; it supports visualization of all the features of the mzIdentML format. The mzidLibrary is a software library containing routines for importing data from external search engines, post-processing identification data (such as false discovery rate calculations), combining results from multiple search engines, performing protein inference, setting identification thresholds, and exporting results from mzIdentML to plain text files. The mzidValidator is able to process files and report warnings or errors if files are not correctly formatted or contain some semantic error. We anticipate that these developments will simplify adoption of the new standard in proteomics laboratories and the integration of mzIdentML into other software tools. All three tools are freely available in the public domain.
    Screening methods and recent developments in the detection of anticoccidials
    Huet, A.C. ; Bienenmann-Ploum, M.E. ; Vincent, U. ; Delahaut, P. - \ 2013
    Analytical and Bioanalytical Chemistry 405 (2013)24. - ISSN 1618-2642 - p. 7733 - 7751.
    tandem mass-spectrometry - performance liquid-chromatography - linked-immunosorbent-assay - time-resolved fluoroimmunoassay - fluorescence polarization immunoassay - uv spectrophotometric detection - antibody-based immunoassay - feed additive nicarbazin - chain v
    This article presents a review of the current trends in the analysis of coccidiostats in various matrices, focusing principally on screening and rapid methods. Coccidiosis is an infectious disease having a high negative impact on the animal industry. Drugs are therefore necessary to prevent and/or to combat this disease. However, it is also of crucial importance that these veterinary drugs do not enter the human food chain. European legislation has therefore established the boundaries for the use of coccidiosats and has also addressed the unavoidable problem of cross-contamination of the feed, mainly caused by the use of the same production lines. Consequently there is a need for analytical methods and/or analytical strategies for the monitoring and control of the residues of anticoccidials, both in feed and in the resulting matrices for human consumption. In the frame of the European collaborative project CONffIDENCE, such attempts to establish the required analytical tools were made, which required beforehand a review of the state of the art in this domain. Aiming at this objective, in this review we consider themost interesting publications since 2000. In essence, both a rapid approach with mainly immunoassays and chromatographic methods were developed. To date, the obstacle to routine use of the first approach has been its inability to detect more than two compounds simultaneously, but recent developments in flow cytometry have made it possible to detect six coccidiostats at once. On the other hand, an increasingly popular approach for detecting multiple coccidiostats simultaneously is liquid chromatography coupledwith tandemmass spectrometry. There remains a need to adapt these analytical methods to legislative requirements.
    Sodiation as a tool for enhancing the diagnostic value of MALDI-TOF/TOF-MS spectra of complex astaxanthin ester mixtures from Haematococcus pluvialis
    Weesepoel, Y.J.A. ; Vincken, J.P. ; Pop, R.M. ; Liu, K. ; Gruppen, H. - \ 2013
    Journal of Mass Spectrometry 48 (2013)7. - ISSN 1076-5174 - p. 862 - 874.
    tandem mass-spectrometry - desorption ionization maldi - fatty-acid esters - carotenoids - identification - microalgae
    The microalga Haematococcus pluvialis produces the pigment astaxanthin mainly in esterified form with a multitude of fatty acids, which results in a complex mixture of carotenol mono- and diesters. For rapid fingerprinting of these esters, matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF/TOF-MS) might be an alternative to traditional chromatographic separation combined with MS. Investigation of ionization and fragmentation of astaxanthin mono- and diester palmitate standards in MALDI-TOF/TOF-MS showed that sodium adduct parent masses [M + Na]+ gave much simpler MS2 spectra than radical / protonated [M]+¿ / [M+H]+ parents. [M + Na]+ fragments yielded diagnostic polyene-specific eliminations and fatty acid neutral losses, whereas [M]+¿ / [M+H]+ fragmentation resulted in a multitude of non-diagnostic daughters. For diesters, a benzonium fragment, formed by polyene elimination, was required for identification of the second fatty acid attached to the astaxanthin backbone. Parents were forced into [M + Na]+ ionization by addition of sodium acetate, and best signal-to-noise ratios were obtained in the 0.1 to 1.0mM range. This method was applied to fingerprinting astaxanthin esters in a crude H. pluvialis extract. Prior to MALDI-TOF/TOF-MS, the extract was fractionated by normal phase Flash chromatography to obtain fractions enriched in mono- and diesters and to remove pheophytin a, which compromised monoester signals. All 12 types of all-trans esterified esters found in LC were identified with MALDI-TOF/TOF-MS, with the exception of two minor monoesters.
    Occurrence of the microcystins MC-LW and MC-LF in Dutch surface waters and their contribution to total microcystin toxicity
    Faassen, E.J. ; Lurling, M. - \ 2013
    Marine Drugs 11 (2013)7. - ISSN 1660-3397 - p. 2643 - 2654.
    tandem mass-spectrometry - cyanobacterial toxins - different hydrophobicities - aeruginosa - blooms - nodularin - province - bogoria - samples - china
    Microcystins (MCs) are the most frequently found cyanobacterial toxins in freshwater systems. Many MC variants have been identified and variants differ in their toxicity. Recent studies showed that the variants MC-LW and MC-LF might be more toxic than MC-LR, the variant that is most abundant and mostly used for risk assessments. As little is known about the presence of these two variants in The Netherlands, we determined their occurrence by analyzing 88 water samples and 10 scum samples for eight MC variants ((dm-7-)MC-RR, MC-YR, (dm-7-)MC-LR, MC-LY, MC-LW and MC-LF) by liquid chromatography with tandem mass spectrometry detection. All analyzed MC variants were detected, and MC-LW and/or MC-LF were present in 32% of the MC containing water samples. When MC-LW and MC-LF were present, they contributed to nearly 10% of the total MC concentrations, but due to their suspected high toxicity, their average contribution to the total MC toxicity was estimated to be at least 45%. Given the frequent occurrence and possible high toxicity of MC-LW and MC-LF, it seems better to base health risk assessments on the toxicity contributions of different MC variants than on MC-LR concentrations alone
    Organophosphorus flame-retardant and plasticizer analysis, including recommendations form the first worldwide interlaboratory study
    Brandsma, S.H. ; Boer, J. de; Leonards, P.E.G. ; Cofino, W.P. ; Covaci, A. - \ 2013
    TrAC : Trends in Analytical Chemistry 43 (2013). - ISSN 0165-9936 - p. 217 - 228.
    tandem mass-spectrometry - indoor environments - gas-chromatography - population characteristics - chemical-ionization - organic-compounds - phthalate-esters - water samples - new-model - air
    The first worldwide interlaboratory study on organophosphorus flame retardants (PFRs) was organized to improve the quality of the data reported in the literature. The study involved standard solutions, dust, fish oil and sediment samples. The differences in coefficients of variation (CV) between the samples were related more to PFR concentration (with high blanks being reported by some laboratories) and less to matrix type. Not all participating laboratories suffered from blank problems, which indicated that it was possible to control the blanks. We include recommendations on how to improve analytical performance, especially to reduce contamination of blanks.
    Critical evaluation of LC-MS-based methods for simultaneous determination of deoxynivalenol, ochratoxin A, zearalenone, aflatoxins, fumonisins and T-2/HT-2 toxins in maize
    Girolamo, A. De; Solfrizzo, M. ; Lattanzio, V.M.T. ; Stroka, J. ; Alldrick, A. ; Egmond, H.P. van; Visconti, A. - \ 2013
    World Mycotoxin Journal 6 (2013)3. - ISSN 1875-0710 - p. 317 - 334.
    tandem mass-spectrometry - performance liquid-chromatography - multi-mycotoxin determination - immunoaffinity cleanup - ht-2 toxins - cereals - ms/ms - food - trichothecenes - t-2
    The results of a proficiency test for the LC-MS/(MS) determination of up to 11 mycotoxins (aflatoxins B1, B2, G1 and G2, fumonisins B1 and B2, ochratoxin A, deoxynivalenol, T-2 and HT-2 toxins and zearalenone) in maize were evaluated to identify possible strengths and weaknesses of various methodologies used by the 41 participating laboratories. The majority of laboratories (56%) used mixtures of acetonitrile:water for extraction. Other laboratories used methanol:water mixtures (17%) or performed two consecutive extractions with phosphate buffer solution (PBS) followed by methanol (15%). Few laboratories used mixtures of acetonitrile:water:methanol (7%), water:ethyl acetate (2.5%) or PBS alone (2.5%). The majority of laboratories (58%) used a clean-up step prior to chromatography. The remaining laboratories analysed crude extracts (37%) or used a mixed approach (5%). The amount of sample equivalent injected into LC-MS/(MS) ranged between 0.1-303 mg for purified extracts and 0.08-20 mg for directly analysed crude extracts. External (54%), matrix-matched (22%) or stable isotope-labelled internal standards calibration (24%) were used for toxin quantification. In general, extraction mixtures of water with acetonitrile, methanol or both provided good results for quantitative extraction of mycotoxins from maize. Laboratories using sample extract clean-up reported acceptable results for the majority of mycotoxins. Good results were also obtained by laboratories that analysed crude extracts although a high variability of results was observed for all tested mycotoxins. Matrix-matched calibration or isotope-labelled internal standards efficiently compensated matrix effects whereas external calibration gave reliable results by injecting =10 mg of matrix equivalent amounts. Unacceptable high recovery and high variability of fumonisin results were obtained by the majority of laboratories, which could not be explained and thus require further investigation. These findings provide the basis for the optimization and selection of methods to be used in future interlaboratory validation studies to derive their performance characteristics for simultaneous determination of mycotoxins in maize.
    Developments in mycotoxin analysis: an update for 2011-2012
    Shephard, G.S. ; Berthiller, F. ; Burdaspal, P. ; Crews, C. ; Jonker, M.A. ; Krska, R. ; MacDonald, S. ; Malone, R.J. ; Maragos, C. ; Sabino, M. ; Solfrizzo, M. ; Egmond, H.P. van; Whitaker, T.B. - \ 2013
    World Mycotoxin Journal 6 (2013)1. - ISSN 1875-0710 - p. 3 - 30.
    performance liquid-chromatography - tandem mass-spectrometry - solid-phase extraction - immunoaffinity column cleanup - surface-plasmon resonance - aflatoxin m-1 contamination - linked-immunosorbent-assay - thin-layer-chromatography - lateral flow immunoassay - di
    This review highlights developments in mycotoxin analysis and sampling over a period between mid-2011 and mid-2012. It covers the major mycotoxins aflatoxins, Alternaria toxins, ergot alkaloids, fumonisins, ochratoxin, patulin, trichothecenes, and zearalenone. A section on mycotoxins in botanicals and spices is also included. Methods for mycotoxin determination continue to be developed using a wide range of analytical systems ranging from rapid immunochemical-based methods to the latest advances in tandem mass spectrometry. This review follows the format of previous reviews in this series (i.e. sections on individual mycotoxins), but due to the rapid spread and developments in the field of multimycotoxin methods by LC-MS/MS, a separate section has been devoted to advances in this area of research.
    Selectivity in the sample preparation for the analysis of drug residues in products of animal origin using LC-MS
    Berendsen, B.J.A. ; Stolker, A.A.M. ; Nielen, M.W.F. - \ 2013
    TrAC : Trends in Analytical Chemistry 43 (2013). - ISSN 0165-9936 - p. 229 - 239.
    tandem mass-spectrometry - quantitative trace analysis - solid-phase extraction - veterinary drugs - antibiotic-residues - multiclass method - environmental-samples - multiresidue method - screening method - food analysis
    Sample preparation is critical in relation to analysis time, sample throughput and therefore analysis costs. Due to recent advances in liquid chromatography-mass spectrometry (LC-MS) instrumentation, the detection of many compounds within one run became possible, and methods for the simultaneous analysis of different compound groups were developed. To be able to analyze compounds with different physical and chemical properties simultaneously, generic, non-selective sample-preparation procedures are applied. The most frequently reported generic sample-preparation methods are a solvent extraction only, solid-phase extraction and a Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) approach. These multi-analyte methods – sometimes including more than 150 different compounds – are of much interest for analytical laboratories due to their reduction in costs. A clear drawback of generic sample-preparation procedures is the occurrence of abundant matrix effects, which compromise detection limits, quantitative aspects, method selectivity and maintenance frequency. In contrast to the trend towards non-selective sample preparation, an opposite trend towards more selective sample-preparation methods is expected to be able to confirm the identity of compounds unambiguously (e.g., stereoisomers). This review gives an overview of generic sample-preparation procedures in the analysis of veterinary drug residues in products of animal origin using LC-MS as the detection technique and an outlook towards expected future trends.
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