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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    National Reference Laboratories WFSR : Annual report 2018
    Noordam, M.Y. ; Silletti, E. ; Alewijn, A. ; Scholtens, I.M.J. ; Jong, J. de; Raamsdonk, L. aan; Lasaroms, J.J.P. ; Gerssen, A. ; Lee, M.K. van der; Mol, J.G.J. ; Leeuwen, S.P.J. van - \ 2019
    Wageningen : Wageningen University & Research (WFSR-report 2019.011) - 51
    National Reference Laboratories RIKILT : annual report 2017
    Leeuwen, S.P.J. van; Mol, J.G.J. ; Lee, M.K. van der; Gerssen, A. ; Lasaroms, J.J.P. ; Sterk, S.S. ; Raamsdonk, L. aan; Jong, J. de; Scholtens, I.M.J. ; Alewijn, A. ; Silletti, E. ; Ginkel, L. van; Noordam, M.Y. ; Meijer, N. - \ 2018
    Wageningen : RIKILT Wageningen University & Research (RIKILT-report 2018.009) - 51
    National Reference Laboratories RIKILT Wageningen University & Research : annual report 2016
    Leeuwen, S.P.J. van; Mol, J.G.J. ; Lee, M.K. van der; Gerssen, A. ; Lasaroms, J.J.P. ; Sterk, S.S. ; Raamsdonk, L.W.D. van; Jong, J. de; Scholtens-Toma, I.M.J. ; Alewijn, M. ; Weesepoel, Y.J.A. ; Ginkel, L.A. van; Meijer, Nathan ; Noordam, M.Y. - \ 2017
    Wageningen : RIKILT Wageningen University & Research (RIKILT Report 2017.007) - 49
    reference standards - laboratories - food legislation - europe - annual reports - food safety - food quality - feeding standards - referentienormen - laboratoria - voedingsmiddelenwetgeving - europa - jaarverslagen - voedselveiligheid - voedselkwaliteit - voedingsnormen
    National Reference Laboratories (NRLs) are part of the system responsible for the control and enforcement of EU food and feed law. RIKILT Wageningen University & Research has been designated as the NRL for twelve subjects. The tasks of a NRL depend on its research field. This report gives an overview of the activities performed by all of RIKILT's NRLs in 2016.
    Dietary supplement for energy and reduced appetite containing the β-agonist isopropyloctopamine leads to heart problems and hospitalisations
    Bovee, Toine F.H. ; Mol, Hans G.J. ; Bienenmann-Ploum, Monique E. ; Heskamp, Henri H. ; Bruchem, Gerard D. van; Ginkel, Leendert A. van; Kooijman, Martin ; Lasaroms, Johan J.P. ; Dam, Ruud van; Hoogenboom, Ron L.A.P. - \ 2016
    Food Additives & Contaminants. Pt. A, Chemistry, Analysis, Control, Exposure & Risk Assessment 33 (2016)5. - ISSN 1944-0049 - p. 749 - 759.
    Biosensor - enforcement - health risks - internet - supplements - web shops

    In 2013 the Dutch authorities issued a warning against a dietary supplement that was linked to 11 reported adverse reactions, including heart problems and in one case even a cardiac arrest. In the UK a 20-year-old woman, said to have overdosed on this supplement, died. Since according to the label the product was a herbal mixture, initial LC-MS/MS analysis focused on the detection of plant toxins. Yohimbe alkaloids, which are not allowed to be present in herbal preparations according to Dutch legislation, were found at relatively high levels (400–900 mg kg–1). However, their presence did not explain the adverse health effects reported. Based on these effects the supplement was screened for the presence of a β-agonist, using three different biosensor assays, i.e. the validated competitive radioligand β2-adrenergic receptor binding assay, a validated β-agonists ELISA and a newly developed multiplex microsphere (bead)-based β-agonist assay with imaging detection (MAGPIX®). The high responses obtained in these three biosensors suggested strongly the presence of a β-agonist. Inspection of the label indicated the presence of N-isopropyloctopamine. A pure standard of this compound was bought and shown to have a strong activity in the three biosensor assays. Analysis by LC-full-scan high-resolution MS confirmed the presence of this ‘unknown known’ β3-agonist N-isopropyloctopamine, reported to lead to heart problems at high doses. A confirmatory quantitative analysis revealed that one dose of the preparation resulted in an intake of 40–60 mg, which is within the therapeutic range of this compound. The case shows the strength of combining bioassays with chemical analytical techniques for identification of illegal pharmacologically active substances in food supplements.

    Possible contamination with clenbuterol from treated veal calves to untreated pen mates
    Groot, M.J. ; Lasaroms, J.J.P. ; Bennekom, E.O. van; Hende, J. van; Nielen, M.W.F. - \ 2013
    Food Additives & Contaminants. Pt. A, Chemistry, Analysis, Control, Exposure & Risk Assessment 30 (2013)6. - ISSN 1944-0049 - p. 1063 - 1067.
    To investigate whether clenbuterol-treated calves could contaminate untreated pen mates, three animal experiments were performed. (1) One calf of a pen of five was treated with clenbuterol by injection (Ventipulmin injection, REG NL 2532, 2.5 mL/100 kg) twice a day for 10 days. (2) In two pens, one animal was treated with clenbuterol via oral administration (Ventipulmin syrup, REG NL 2532, 4 mL/125 kg) for 4 weeks. (3) In two pens, one animal was treated with clenbuterol via the milk (Ventipulmin, REG NL 2532, 2.5 mL/100 kg body weight) twice a day for 10 days. Here, the animal was set apart during treatment, cleaned and put back into the group. Levels of clenbuterol were analysed in hair and urine with LC-MS/MS. Clenbuterol administered by injection could not be transferred from treated to untreated calves. In the second experiment, all pen mates were found positive for clenbuterol in the hair. This contamination was probably due to licking the mouth of the treated animal or saliva from the treated animal spoiling the floor. In the third experiment, no pen mates were found positive for clenbuterol in the hair. Clenbuterol was found in the urine and hair of only treated animals.
    Illegal treatment of barrows with nandrolone ester: effect on growth, histology and residue levels in urine and hair
    Groot, M.J. ; Lasaroms, J.J.P. ; Bennekom, E.O. van; Meijer, T. ; Vinyeta, E. ; Klis, J.D. van der; Nielen, M.W.F. - \ 2012
    Food Additives & Contaminants. Pt. A, Chemistry, Analysis, Control, Exposure & Risk Assessment 29 (2012)5. - ISSN 1944-0049 - p. 727 - 735.
    mass-spectrometry - testosterone - castration - steroids - pigs - 19-nortestosterone - metabolism - estradiol - carcass - boars
    The effect of 17ß-19-nortestosterone (17ßNT) treatment of barrows on residue levels and growth was evaluated. Five barrows were treated three times during the fattening period with 17ßNT phenylpropionate (Nandrosol, nandrolone phenylpropionate 50¿mg/ml,1¿mg/kg body weight). Another five barrows were untreated and five boars (untreated) were kept as positive control. Boars and treated barrows showed a 13 and 9% improvement in growth compared to untreated barrows, with mean final body weights of 121.6, 117.8 and 109.0¿kg, respectively. The bulbourethral glands of the treated barrows were three times heavier than untreated barrows. The histology of the prostate and bulbourethral gland of the treated barrows was comparable to the boars, whereas the control barrows showed atrophic glands. Levels of 17ßNT ester in hair from treated barrows were high, whereas boars and untreated barrows did not show levels above LLQ. It is concluded that analysis of hair can detect illegal treatment with 17ßNT ester in barrows. The size of the bulbourethral gland can also be used for screening in the slaughterhouse.
    Veterinary treatment of cows with isoxsuprine for a caesarian section may temporarily lead to residues in hair of both cow and calf
    Groot, M.J. ; Lasaroms, J.J.P. ; Hende, J. van; Nielen, M.W.F. - \ 2012
    Drug Testing and Analysis 4 (2012)6. - ISSN 1942-7603 - p. 515 - 518.
    tandem mass-spectrometry - hydrochloride - affinity - agonists - bovine - urine - horse
    Isoxsuprine is a beta-agonist that can be used for growth promotion in cattle, but it is also used as registered veterinary medicine. To investigate if veterinary treatment of cows could lead to residues of isoxsuprine in the hair of their newborn calves, an animal experiment was performed. Four cows, treated on veterinary indication with isoxsuprine lactate (Duphaspasmin) before a caesarian section, were included in the experiment. Hair samples from cows and from their calves were analyzed. The animals were shaved every week for 16 weeks and levels of isoxsuprine were measured in hair. In the cows, the levels of isoxsuprine were highest (>15 µg/kg) just after administration of the isoxsuprine lactate. After two weeks in two cows, a sort of plateau was reached and then the levels decreased. After approximately 10-15 weeks the levels were around the CCa level of the method used (0.5 µg/kg). In calves, for the first two weeks after birth, no isoxsuprine was found above CCa level in three of the four animals. At about 20-30 days old, a maximum concentration of 4 µg/kg was found. Then the levels dropped again under the CCa level, after 60 days no levels above CCa level were found. In one animal, the levels never reached CCa level. We conclude that veterinary treatment of cows with isoxsuprine may temporarily lead to low levels of isoxsuprine in the hair of their newborn calves which can be measured for a maximum of 60 days after birth.
    Nandrolone ester turns barrows into boars
    Groot, M.J. ; Bennekom, E.O. van; Lasaroms, J.J.P. ; Vinyeta, E. ; Klis, J.D. van der; Nielen, M.W.F. - \ 2011
    Effect of sample pre-treatment on the determination of steroid esters in hair of bovine calves
    Aqai, P. ; Stolker, A.A.M. ; Lasaroms, J.J.P. - \ 2009
    Journal of Chromatography. A, Including electrophoresis and other separation methods 1216 (2009)46. - ISSN 0021-9673 - p. 8233 - 8239.
    tandem mass-spectrometry - drugs
    The effect of three sample pre-treatment steps, washing, cutting and grinding on the determination of steroid esters in hair is studied. The study is performed by using hair samples obtained after pour-on application of steroid esters to bovine calves. After sample pre-treatment the hair is treated with a mild reducing agent [tris(2-carboxyethyl)phosphine hydrochloride] to extract the steroid esters. After a solid-phase extraction clean-up step the extracts are analysed by using liquid chromatography combined with triple–quadrupole mass spectrometric detection. For the washing step the use of non-organic washing solvents like (warm) water and a solution of 0.1% sodium dodecyl phosphate and organic solutions containing different percentages of methanol are tested. By using the non-organic solvents and the organic solvents with a percentage of methanol
    Detectability of testosterone esters and estradiol benzoate in bovine hair and plasma following pour-on treatment
    Stolker, A.A.M. ; Groot, M.J. ; Lasaroms, J.J.P. ; Nijrolder, A.W.J.M. ; Blokland, M.H. ; Riedmaier, I. ; Becker, C. ; Meyer, H.H.D. ; Nielen, M.W.F. - \ 2009
    Analytical and Bioanalytical Chemistry 395 (2009)4. - ISSN 1618-2642 - p. 1075 - 1087.
    tandem mass-spectrometry - anabolic-steroids - doping control - livestock production - cattle - corticosteroids - stanozolol - nandrolone - samples - misuse
    The abuse of synthetic esters of natural steroids such as testosterone and estradiol in cattle fattening and sports is hard to detect via routine urine testing. The esters are rapidly hydrolysed in vivo into substances which are also endogenously present in urine. An interesting alternative can be provided by the analysis of the administered synthetic steroids themselves, i.e., the analysis of intact steroid esters in hair by liquid chromatography tandem mass spectrometry (LC/MS/MS). However, retrospective estimation of the application date following a non-compliant finding is hindered by the complexity of the kinetics of the incorporation of steroid esters in hair. In this study, the incorporation of intact steroid esters in hair following pour-on treatment has been studied and critically compared with results from intramuscular treatment. To this end animals were pour-on treated with a hormone cocktail containing testosterone cypionate, testosterone decanoate and estradiol benzoate in different carriers. The animals were either treated using injection and pour-on application once or three times having 1 week between treatments using injection and pour-on application. Animals were slaughtered from 10–12 weeks after the last treatment. Both hair and blood plasma samples were collected and analysed by LC/MS/MS. From the results, it is concluded that after single treatment the levels of steroid esters in hair drop to CCß levels (5-20 µg/kg) after 5-7 weeks. When treatment is repeated two times, the CCß levels are reached after 9–11 weeks. Furthermore, in plasma, no steroid esters were detected; not even at the low microgramme per litre level but-in contrast with the pour-on application-after i.m. injection, significant increase of 17ß-testosterone and 17ß-estradiol were observed. These observations suggest that transport of steroid esters after pour-on application is not only performed by blood but also by alternative fluids in the animal so probably the steroid esters are already hydrolysed and epimerized before entering the blood
    Validation and application of a yeast bioassay for screening androgenic activity in calf urine and feed
    Bovee, T.F.H. ; Bor, G. ; Heskamp, H.H. ; Lasaroms, J.J.P. ; Sanders, M.B. ; Nielen, M.W.F. - \ 2009
    Analytica Chimica Acta 637 (2009)1-2. - ISSN 0003-2670 - p. 225 - 234.
    tandem mass-spectrometry - in-vitro - liquid-chromatography - estrogenic activity - recombinant assay - anabolic-steroids - receptor ligands - surface waters - binding - dihydrotestosterone
    Bioassays are valuable tools for combating the illegal use of steroids in cattle fattening. Previously we described the construction and properties of a rapid and robust yeast androgen bioassay stably expressing the human androgen receptor (hAR) and yeast enhanced green fluorescent protein (yEGFP), the latter in response to androgens. In the present study this yeast androgen bioassay was validated as a qualitative screening method for the determination of androgenic activity in calf urine and animal feed. This validation was performed according to EC Decision 2002/657. 20 blank samples were spiked with testosterone, 17¿-methyltestosterone, 19-nortestosterone, 17ß-trenbolone, 17ß-boldenone or 17¿-methylboldenone at 2 or 15 ng mL¿1 in urine and 50 or 100 ng g¿1 in feed. All blank and spiked samples fulfilled the CC¿ and CCß criterions, meaning that all 20 blank samples gave signals below the determined decision limits CC¿ and were thus classified as compliant (¿ = 1%). For each component, at least 19 out of the 20 spiked samples gave a signal above the CC¿ and were thus classified as suspect (ß = 5%). The method was specific, and high amounts of dexamethasone did not interfere with the outcome of the test. Although high levels of 17¿-ethynylestradiol can significantly inhibit the response obtained with low amounts of androgens, that situation is not relevant in veterinary practice. When stored at their specific conditions, the androgens in feed were stable for at least 91 days. Real urine samples from a national control program were screened and a representative part of the compliant and suspect samples were confirmed by gas chromatography¿tandem mass spectrometry
    Comprehensive screening and quantification of veterinary drugs in milk using UPLC-ToF-MS
    Stolker, A.A.M. ; Rutgers, P. ; Oosterink, J.E. ; Lasaroms, J.J.P. ; Peters, R.J.B. ; Rhijn, J.A. van; Nielen, M.W.F. - \ 2008
    Analytical and Bioanalytical Chemistry 391 (2008)6. - ISSN 1618-2642 - p. 2309 - 2322.
    flight mass-spectrometry - growth-promoting agents - residue analysis - strategies - muscle - urine
    Ultra-performance liquid chromatography combined with time-of-flight mass spectrometry (UPLC¿ToF-MS) has been used for screening and quantification of more than 100 veterinary drugs in milk. The veterinary drugs represent different classes including benzimidazoles, macrolides, penicillins, quinolones, sulphonamides, pyrimidines, tetracylines, nitroimidazoles, tranquillizers, ionophores, amphenicols and non-steroidal anti-inflammatory agents (NSAIDs). After protein precipitation, centrifugation and solid-phase extraction (SPE), the extracts were analysed by UPLC¿ToF-MS. From the acquired full scan data the drug-specific ions were extracted for construction of the chromatograms and evaluation of the results. The analytical method was validated according to the EU guidelines (2002/657/EC) for a quantitative screening method. At the concentration level of interest (MRL level) the results for repeatability (%RSD¿
    Multiresidue analysis of beta-agonists in bovine and porcine unrine, feed and hair using liquid chromatography electrospray ionisation tandem mass spectrometry
    Nielen, M.W.F. ; Lasaroms, J.J.P. ; Essers, M.L. ; Oosterink, J.E. ; Meijer, T. ; Sanders, M.B. ; Zuidema, T. ; Stolker, A.A.M. - \ 2008
    Analytical and Bioanalytical Chemistry 391 (2008)1. - ISSN 1618-2642 - p. 199 - 210.
    growth-promoting agents - residue analysis - veterinary drugs - liver - identification - resonance - cleanup - ms
    The use of ß-agonists as growth promoters in cattle breeding is forbidden in many countries for reasons of fair trade and consumer protection. In recent years the use of liquid chromatography (LC) tandem mass spectrometry (MS/MS) has been shown to be the method of choice for the control of ß-agonists. In this study an LC-MS/MS multiresidue analysis method is presented for trace analysis of 22 ß-agonists. A truly generic concept has been designed based on mixed-mode solid-phase extraction and positive electrospray ionisation LC-MS/MS operated in the multiple reaction monitoring mode. This method allows application to a wide variety of sample matrices such as urine, feed and hair, following minor modifications to the analysis procedure only. The method features fit-for-purpose sensitivity in urine as shown by CC¿ and CCß values of less than 0.2 and less than 0.5 ¿g/l respectively, for all ß-agonists studied (terbutaline and reproterol, less than 0.3 and less than 1.0 respectively). Similar but semiquantitative application to feed and hair showed CCß values of less than 10.0 and less than 5.0 ¿g/kg, respectively. A further simplification and improvement is demonstrated using Ultra Performance LC (UPLC¿) and fast-switching MS/MS. The successful validation of this method following the latest EU requirements and its application to real samples demonstrate that a new versatile tool has been achieved for veterinary control of ß-agonists.
    The ultimate veal calf reference experiment: Hormone residue analysis data obtained by gas and liquid chromatography tandem mass spectrometry
    Nielen, M.W.F. ; Lasaroms, J.J.P. ; Essers, M.L. ; Sanders, M.B. ; Heskamp, H.H. ; Bovee, T.F.H. ; Rhijn, J.A. van; Groot, M.J. - \ 2007
    Analytica Chimica Acta 586 (2007)1-2. - ISSN 0003-2670 - p. 30 - 34.
    yeast estrogen bioassay - confirmatory analysis - bovine urine - boldenone - steroids - cattle - calves - feces - androsta-1,4-diene-3,17-dione - 17-alpha-boldenone
    A lifetime controlled reference experiment has been performed using 42 veal calves, 21 males and 21 females which were fed and housed according to European regulations and common veterinary practice. During the experiment feed, water, urine and hair were sampled and feed intake and growth were monitored. Thus for the first time residue analysis data were obtained from guaranteed lifetime-untreated animals. The analysis was focused on the natural hormones estradiol and testosterone and their metabolites, on 17 beta- and 17 alpha-nortestosterone, on 17 beta- and 17 alpha-boldenone and androsta-1,4-diene-3,17-dione (ADD), and carried out by gas chromatography tandem mass spectrometry (GC/MS/MS), an estrogen bioassay and liquid chromatography (LC) MS/MS. Feed, water and hair samples were negative for the residues tested. Female calf urines showed occasionally low levels of 17 alpha-estradiol and 17 alpha-testosterone. On one particular sampling day male veal calf urines showed very high levels of 17 alpha-testosterone (up to 1000 ng mL(-1)), accompanied by lower levels of estrone and 17 beta-testosterone. Despite these extreme levels of natural testosterone, 17 beta-boldenone was never detected in the same urine samples; even 17 alpha-boldenone and ADD were only occasionally beyond CC alpha (maximum levels 2.7 ng ng mL(-1)). The data from this unique experiment provide a set of reference values for steroid hormones in calf urine and demonstrate that 17 beta-boldenone is not a naturally occurring compound in urine samples. (c) 2006 Elsevier B.V. All rights reserved.
    Can high-performance liquid chromatography coupled with fluorescence detection under all conditions be regarded as a sufficiently conclusive confirmatory method for B-group substances?
    Zuidema, T. ; Mulder, P.P.J. ; Lasaroms, J.J.P. ; Stappers, S.J.W. ; Rhijn, J.A. van - \ 2006
    Food Additives and Contaminants 23 (2006)11. - ISSN 0265-203X - p. 1149 - 1156.
    mass-spectrometry - salicylic-acid - surface-water - waste-water - drugs
    Commission Decision 2002/657/EC requires confirmatory analysis of B-group compounds when detected at levels above the permitted limit. In contrast to banned substances, for B-group substances, the use of mass spectrometric techniques is not obligatory and several techniques including liquid chromatography (LC)-ultraviolet light (UV) on two different LC columns and (single-column) high-performance liquid chromatography (HPLC)-fluorescence (Flu) are considered to deliver sufficient evidence for the identification of the detected substance. The analysis of sodium salicylate in animal drinking water collected at poultry farms is presented here as an example to show that even in a simple matrix such as animal drinking water, fluorescence detection in some cases may provide inadequate specificity. Of 50 samples analysed by LC-Flu, 18 tested positive for sodium salicylate. However, only in one sample was the presence of the analyte confirmed with mass spectrometric detection; the others were blank. Consequently, the LC-Flu results obtained were false-non-compliant for sodium salicylate. A second case concerning the analysis of avermectins in milk by HLPC-Flu is briefly described. For a number of samples analysed in the framework of a proficiency test, false non-compliant results for emamectin were reported due to a background interference sometimes present that practically co-eluted with the analyte. The observed retention time difference (1%) was well below the criterion (2.5%) specified in Commission Decision 2002/657/EC. Considering the impact of positive findings on individual farmers as well as on trade, product image and food safety perception by the consumer, it is concluded that also for B-group substances false-non-compliant results should be avoided whenever possible. This is especially important when the results are treated as and are expected to have the same repercussions as in the case of banned A-group substances. In these circumstances, only results obtained by mass spectrometry should be considered for confirmatory purposes
    Screening for estrogen residues in calf urine: Comparison of a validated yeast estrogen bioassay and gas chromatography-tandem mass spectrometry
    Nielen, M.W.F. ; Bovee, T.F.H. ; Heskamp, H.H. ; Lasaroms, J.J.P. ; Sanders, M.B. ; Rhijn, J.A. van; Groot, M.J. ; Hoogenboom, L.A.P. - \ 2006
    Food Additives and Contaminants 23 (2006)11. - ISSN 0265-203X - p. 1123 - 1131.
    green fluorescent protein - liquid-chromatography - anabolic-steroids - identification - expression - beta
    Within the European Union, the control for residues of illegal hormones in food-producing animals is based on urine analysis for a few target analytes using gas chromatography/mass spectrometry and/or liquid chromatography¿tandem mass spectrometry. Recently, we developed a robust yeast bioassay screening tool for estrogens, which was validated as a qualitative screening method in accordance with EC decision 2002/657/EC. In this study, we present long-term performance data and a comparison of urine data obtained with this bioassay, and data from an established gas chromatography¿tandem mass spectrometry (GC/MS/MS) confirmatory analysis method. More than 120 calf urine samples from a controlled reference experiment were analysed using both protocols. According to the GC/MS/MS method, only the natural estrogens 17¿-estradiol and estrone were present in the non-compliant samples. The bioassay was less sensitive than GC/MS/MS for the relatively weak estrogenic compound 17¿-estradiol, in accordance with expectations. Assuming that application of the mass spectrometric method is considered beyond reasonable doubt, the bioassay performed very well: only 5.6% of the calf urine samples found compliant in GC/MS/MS were screened false suspect in the bioassay screening method. The bioassay results of non-compliant urine samples under routine conditions were as predicted, taking into account the relative estrogenicity of the natural estrogens 17¿-estradiol and estrone vs. 17ß-estradiol. Only one sample was screened false negative for 17¿-estradiol and estrone. Application of this fast and simple estrogen bioassay in routine surveillance and control can significantly reduce GC/MS/MS sample workload and allow higher percentages of animals to be screened for potential hormone abuse
    A dual-isotope-labeling method of studying the bioavailablity of hexaglutamyl folic acid relative to that of monoglutamyl folic acid in humans by using multiple orally administered low doses
    Boonstra, A. ; Verhoef, P. ; West, C.E. ; Rhijn, J.A. van; Breemen, R.B. van; Lasaroms, J.J.P. ; Garbis, S.D. ; Katan, M.B. ; Kok, F.J. - \ 2006
    American Journal of Clinical Nutrition 84 (2006)5. - ISSN 0002-9165 - p. 1128 - 1133.
    performance liquid-chromatography - folate bioavailability - food folate - polyglutamyl folate - urinary-excretion - women - absorption - availability - homocysteine - bioefficacy
    Background: The bioavailability of dietary folate may be hampered by the need of the glutamate moieties to be deconjugated before absorption. Previous studies comparing the bioavailabilities of polyglutamyl and monoglutamyl folic acid had inconsistent results. Objective: The objective was to estimate the bioavailability of polyglutamyl relative to that of monoglutamyl folic acid by using a sensitive stable-isotope approach that allowed for the administration of multiple low doses in humans. Design: Twenty subjects aged 20-50 y ingested 2 capsules daily for 28 d; each capsule contained approximate to 50 nmol [C-13(6)]hexaglutamyl and approximate to 50 nmol [C-13(11)]monoglutamyl folic acid. Amounts of the isotopically labeled compounds in the capsules were verified by various methods. The degrees of isotopic enrichment of plasma 5-methyltetrahydrofolate with C-13(6) and C-13(11) were measured by using liquid chromatography tandem mass spectrometry, and the ratio of C-13(6) to C-13(11) (C-13(6): C-13(11)) in plasma on day 28 was used as a measure of their relative bioavailability. Results: The C-13(11): C-13(6) in plasma 5-methyltetrahydrofolate reached equilibrium on day 4 and was 0.66 (95% CI: 0.58, 0.74) on day 28. The C-13(11): C-13(6) content in the capsules varied between 1.18 and 1.96. After correction for this ratio, the estimated bioavailability of hexaglutamyl relative to that of monoglutamyl folic acid was >= 78%. Conclusion: Multiple dosing of low amounts of labeled folic acid is a sensitive, accurate, and efficient method of measuring the relative bioavailability of folic acid compounds, provided that the administered doses can be reliably assessed.
    Multi residue screening of intact testosterone esters and boldenone undecylenate in bovine hair using liquid chromatography electrospray tandem mass spectrometry
    Nielen, M.W.F. ; Lasaroms, J.J.P. ; Mulder, P.P.J. ; Hende, J. van; Rhijn, J.A. van; Groot, M.J. - \ 2006
    Journal of Chromatography. B, Analytical technologies in the biomedical and life sciences 830 (2006)1. - ISSN 1570-0232 - p. 126 - 134.
    anabolic-steroids - doping control - cattle - corticosteroids - stanozolol - estradiol - samples - urine
    The abuse of esters of natural androgenic steroids in cattle fattening and sports is hard to control via routine urine testing. The esters are rapidly hydrolysed in vivo into substances which are also endogenously present in urine. In veterinary control strange findings of 17ß-testosterone and 17¿-testosterone in urine are often ignored because of the lack of statistically sound reference data of naturally occurring levels. An interesting alternative for inconclusive urine analyses in veterinary control can be provided by the analysis of the administered steroids themselves, i.e. the analysis of intact steroid esters in hair. Unfortunately, the analysis of intact steroid esters is complicated not only by the vulnerability of the esters which precludes alkaline hydrolysis of the hair, but also by the wide polarity range of short and long-chain esters yielding very poor recoveries for either the one or the other. In this study, a multi-steroid esters LC/MS/MS screening method is presented for trace analysis of the synthetic intact esters of 17ß-testosterone and the undecylenate ester of 17ß-boldenone in bovine hair. The method, requiring only 200 mg of pulverised hair, features a mild digestion procedure using tris(2-carboxyethyl)phosphine hydrochloride (TCEP) and the use of four deuterium-labelled steroid esters as internal standards covering the wide polarity range of the analytes. In spiked hair samples for most of the analytes the limit of detection and the accuracy using isotope dilution were 2¿5 ng/g and 97¿105%, respectively. The applicability was demonstrated using hair samples from a controlled experiment in which six bovines were injected intramuscularly with two different doses of two commercial mixtures of testosterone esters, and with two different doses of boldenone undecylenate. Depending on the dose all administered testosterone- and boldenone esters were found to be incorporated in bovine hair following a single intramuscular injection, except testosterone propionate which dose might have been too low
    Confirmatory analysis of traces of malachite green and its main metabolite leucomalachite green in muscle tissue of atlantic salmon
    Rhijn, J.A. van; Mulder, P.P.J. ; Baardewijk, F. van; Brinke, E.M. te; Lasaroms, J.J.P. - \ 2004
    In: residues of veterinary drugs in food: proceedings of the EuroResidue Conderence V, 10-12 May 2004, Noordwijkerhout, The Netherlands Utrecht : Faculty of Veterinary Medicine - p. 808 - 813.
    Optimization of a liquid chromatography-tandem mass spectrometry method for quantification of the plant lignans secoisolariciresinol, matairesinol, lariciresinol and pinoresinol in foods
    Milder, I.E.J. ; Arts, I.C.W. ; Venema, D.P. ; Lasaroms, J.J.P. ; Wähälä, K. ; Hollman, P.C.H. - \ 2004
    Journal of Agricultural and Food Chemistry 52 (2004)15. - ISSN 0021-8561 - p. 4643 - 4651.
    hormone-binding globulin - electrode array detection - breast-cancer risk - serum concentrations - flax seed - urinary-excretion - enterolactone - phytoestrogens - metabolism - isoflavonoids
    A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the quantification of the four major enterolignan precursors [secoisolariciresinol, matairesinol, lariciresinol, and pinoresinol] in foods. The method consists of alkaline methanolic extraction, followed by enzymatic hydrolysis using Helix pomatia (H. pomatia) -glucuronidase/sulfatase. H. pomatia was selected from several enzymes based on its ability to hydrolyze isolated lignan glucosides. After ether extraction samples were analyzed and quantified against secoisolariciresinol-d8 and matairesinol-d6. The method was optimized using model products: broccoli, bread, flaxseed, and tea. The yield of methanolic extraction increased up to 81°when it was combined with alkaline hydrolysis. Detection limits were 4-10 g/(100 g dry weight) for solid foods and 0.2-0.4 g/(100 mL) for beverages. Within- and between-run coefficients of variation were 6-21 and 6-33°respectively. Recovery of lignans added to model products was satisfactory (73-123) except for matairesinol added to bread (51-55)
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