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See detailA new easy method for specific measurement of active myeloperoxidase in human biological fluids and tissue extracts
Franck, Thierry ULg; Kohnen, Stephan; Zouaoui Boudjeltia, Karim et al

in Talanta (2009), 80

The SIEFED (“Specific Immunological Extraction Followed by Enzymatic Detection”) method already developed for the specific detection of the activity of equine myeloperoxidase (MPO) was adapted for the ... [more ▼]

The SIEFED (“Specific Immunological Extraction Followed by Enzymatic Detection”) method already developed for the specific detection of the activity of equine myeloperoxidase (MPO) was adapted for the specific measurement of active human MPO in biological fluids or tissue extracts. [less ▲]

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See detailDirect determination of tagitinin C in Tithonia diversifolia leaves by on-line coupling of supercritical carbon dioxide extraction to FT-IR spectroscopy by means of optical fibres
Ziemons, Eric ULg; Barillaro, Valéry; Rozet, Eric ULg et al

in Talanta (2007), 71(2), 911-917

Supercritical fluid extraction (SFE) with carbon dioxide as extraction medium was on-line coupled to a FT-IR spectrometer equipped with a Mercury Cadmium Telluride (MCT) detector using a tailor-made high ... [more ▼]

Supercritical fluid extraction (SFE) with carbon dioxide as extraction medium was on-line coupled to a FT-IR spectrometer equipped with a Mercury Cadmium Telluride (MCT) detector using a tailor-made high-pressure fibre optic flow cell. This method was optimised and developed for the monitoring in real time and the quantification of dynamic extractions of tagitinin C from Tithonia.diversifolia leaves. In order to demonstrate the method ability to allow the direct quantification of tagitinin C in the extract medium the standard addition method was used. The area integration Of Curves obtained by plotting the absorbance of the highly specific C=O stretching vibration at 1668 cm(-1) versus time (i.e. extractograms) was used as instrumental response. The SFE/FT-IR process was successfully validated using the accuracy profile as decision tool. On this basis, a linear regression model was chosen for the calibration curve. The relative standard deviation for repeatability and intermediate precision were between 0.8 and 3.1 %, respectively. Moreover, the method was found to be accurate as the two-sided 95% beta-expectation tolerance interval did not exceed the acceptance limits of 85 and 115% on the analytical range investigated (500-2500 mu g of added amount of tagitinin Q. The proposed method allowed the non-destructive extraction of tagitinin C and its on-line quantitative determination in less than 25 min thus facilitating the subsequent experiments or the pharmacological studies performed on this compound. [less ▲]

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See detailDetermination of total water content in inulin using the volumetric Karl Fischer titration
Ronkart, S. N.; Paquot, Michel ULg; Fougnies, C. et al

in Talanta (2006), 70(5), 1006-1010

A new sample preparation method for the water content determination of mulin by volumetric Karl Fischer (KF) titration was developed and compared to the usual method of introducing the sample directly in ... [more ▼]

A new sample preparation method for the water content determination of mulin by volumetric Karl Fischer (KF) titration was developed and compared to the usual method of introducing the sample directly in the methanol-based working medium, modified or not by formamide (1:3, v/v) in order to increase sample solubility. In the proposed method, inulins were externally prepared by dissolving them in pure formamide (2.5:7.5, w/w). The time of analysis of the liquid/liquid reaction of the new method between the dissolved sample and the reaction medium is about 1-2 min, while the usual KF method is stopped after the 10 min delay time. The developed method permits the determination of water included in the crystals of the sample, confirmed by analysing both crystalline and amorphous mulin samples. Another advantage of this new method is its applicability for the water content determination of other polysaccharides that are not readily soluble in the working medium. Moreover. water content determination can be done by any type of volumetric KF titrator, as this proposed technique is not dependent on any additional tools such as a built-in homogeniser or a heatable titration beaker. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailLC method for the determination of R-timolol in S-timolol maleate: Validation of its ability to quantify and uncertainty assessment.
Marini Djang'Eing'A, Roland ULg; Chiap, Patrice ULg; Boulanger, Bruno ULg et al

in Talanta (2006), 68(4), 1166-1175

This article presents the validation results of a chiral liquid chromatographic (LC) method previously developed for the quantitative determination of R-timolol in S-timolol maleate samples. A novel ... [more ▼]

This article presents the validation results of a chiral liquid chromatographic (LC) method previously developed for the quantitative determination of R-timolol in S-timolol maleate samples. A novel validation strategy based on the accuracy profiles was used to select the most appropriate regression model, to assess the method accuracy within well defined acceptance limits and to determine the limits of quantitation as well as the concentration range. The validation phase was completed by the investigation of the risk profiles of various acceptable regression models in order to ensure the risk of obtaining the future measurements outside the acceptance limits fixed a priori. On the other hand, the present paper also shows how data used in this validation approach can be used to estimate the measurement uncertainty. The uncertainty derived from beta-expectation tolerance interval (sigma(Tol)(2)), which is equal to the uncertainty of measurements as well as the expanded uncertainty (U(x)) using a coverage factor k=2 was estimated. The uncertainty estimates obtained from validation data were finally compared with those obtained from interlaboratory and robustness studies. [less ▲]

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See detailA strategy to identify specific biomarkers related to the effects of a PCDD/F mixture on the immune system of marine mammals
Brenez, C.; Gerkens, P.; Mazzucchelli, Gabriel ULg et al

in Talanta (2004), 63(5), 1225-1230

The cell lines chosen have demonstrated a positive response in terms of cell proliferation and associated modifications in proteins content, evaluated through DNA and proteins synthesis, at ... [more ▼]

The cell lines chosen have demonstrated a positive response in terms of cell proliferation and associated modifications in proteins content, evaluated through DNA and proteins synthesis, at environmentally relevant dose of dioxins, brought by a typical environmental PCDD/F mixture. The response is time and species dependent. After completion of the identification of proteins affected by the intoxication, we will identify a set of specific proteins whose expression is correlated to the dioxin dose and submit the cell culture to the treatment with a single chemical as well as with mixtures. We hope that this will allow us to construct and validate a set of protein biomarkers of exposure to pollutants that will show a predictive aspect for unknown chemicals. The quantitative analysis of the set of biomarkers can then be a more specific bioassay and an alternative to physico-chemical or other already established bioanalytical methods for screening purposes. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailPTV-LV-GC/MS/MS as screening and complementary method to HRMS for the monitoring of dioxin levels in food and feed
Eppe, Gauthier ULg; Focant, Jean-François ULg; Pirard, Catherine et al

in Talanta (2004), 63(5), 1135-1146

Recent developments in trapping efficiency inside ion trap mass spectrometer permitted to lower instrument detection limit (IDL). An IDL of 200 fg mul(-1) injected with a signal-to-noise ratio of 5:1 for ... [more ▼]

Recent developments in trapping efficiency inside ion trap mass spectrometer permitted to lower instrument detection limit (IDL). An IDL of 200 fg mul(-1) injected with a signal-to-noise ratio of 5:1 for tetrachlorodibenzo-p-dioxin (TCDD) was obtained by gas chromatography coupled to a quadrupole ion storage mass spectrometer in tandem mode (GC/MS/MS). Coupling large volume programmable temperature vaporizer (PTV-LV) injection to GC/MS/MS provides an alternative and complementary method to classical splitless-GC injection connected to high-resolution mass spectrometry (splitless-GC/HRMS) method for dioxin monitoring in food and feed. An injection volume of 10 mul was found to be the best compromise between the sensitivity requirements and the robustness required for a high throughput method. PTV-LV-GC/MS/MS and Splitless-GC/HRMS were compared by performing analysis on five different matrices such as beef fat, yolk eggs, milk powder, animal feed and serum samples covering a concentration range of two orders of magnitude (i.e. 0.2-25 ng WHO-TEQ kg(-1)). An analysis of variance (ANOVA) was carried out. Fisher tests pointed out that the method effect for all the 2,3,7,8 congeners was not significant, indicating that the null hypothesis (H-0: mu(1) = mu(2) = ... = mu(n)) was not rejected. Moreover, the interaction effects between methods and matrices were not significant for most of the 2,3,7,8 congeners. However, three congeners (2,3,7,8-TCDF; 1,2,3,4,7,8-HxCDD and I,2,3,4,6,7,8-HpCDD) were characterized by P-values lower than the significance level (alpha = 0.05). In toxic equivalence (TEQ), the study showed that no significant bias was observed between the two methods. Consequently, PTV-LV-GC/MS/MS is an attractive technique and can be used as a cost effective complementary method to HRMS for dioxin levels monitoring in food and feed. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailImportance of clean-up for comparison of TEQ-values obtained by CALUX and chemo-analysis
Van Wouwe, N.; Windal, I.; Vanderperren, H. et al

in Talanta (2004), 63(5), 1269-1272

This paper presents Chemically Activated LUciferine gene eXpression (CALUX) TEQ-values obtained for nine plasma samples following two different purification procedures, one of them involving fractionation ... [more ▼]

This paper presents Chemically Activated LUciferine gene eXpression (CALUX) TEQ-values obtained for nine plasma samples following two different purification procedures, one of them involving fractionation. CALUX results obtained for the dioxin (DX) and dioxin + PCB (DX + PCB) fractions were then compared to the GC-HRMS TEQ-values calculated for the 17 polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (17 PCDD/F) and 17 PCDD/F + 4 cPCB congeners, respectively. The overestimation of the CALUX (DX fraction) TEQ-values in comparison with the chemo-analyses of the 17 PCDD/F is mainly explained by the presence of other AhR agonists, like brominated compounds. Otherwise, the constancy of the CALUX (DX + PCB fraction) TEQ-value which compares to increasing the GC-HRMS (17 PCDD/F + 4 cPCB) TEQ results raises questions concerning (1) the significance of CALUX results obtained without fractionation as well as (2) the toxicological effect of a cocktail of contaminants on the human health. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailValidation of the CALUX bioassay for PCDD/F analyses in human blood plasma and comparison with GC-HRMS
Van Wouwe, N.; Windal, I.; Vanderperren, H. et al

in Talanta (2004), 63(5), 1157-1167

Following the dioxin crisis of 1999, several studies were conducted to assess the impact of this crisis on the dioxin body burden in the Belgian population. The Scientific Institute of Public Health ... [more ▼]

Following the dioxin crisis of 1999, several studies were conducted to assess the impact of this crisis on the dioxin body burden in the Belgian population. The Scientific Institute of Public Health identified a population from whom plasma samples were available and from whom, during the follow up survey, plasma samples were obtained in 2000. In total, 496 samples were collected for GC-HRMS and CALUX analyses to verify statistical assessment conclusions. This study was seen as an opportunity to validate the CALUX bioassay for biological sample analysis and to compare toxic equivalency (TEQ) values obtained by the reference GC-HRMS technique and by the screening method. This article focuses on the validation results of the CALUX bioassay for the analyses of the dioxin fractions of blood plasma. The sample preparation is based on a liquid-liquid extraction, followed by an acid silica in series with an activated carbon clean-up. A good recovery (82%) and reproducibility (coefficient of variation less than 25%) were found for this method. Based on 341 plasma samples, a significant correlation was established between the bioassay and chemical method (R = 0.64). However, a proportional systematic error was observed when the results obtained with the CALUX bioassay were regressed with the results from the GC-HRMS analyses. The limit of quantification (LOQ) used to calculate TEQ values from the GC-HRMS determinations, the use of the relative potency values instead of the toxic equivalent factor and the potential of CALUX bioassay to measure all compounds with affinity for the AhR may partly explain this proportional systematic error. Nevertheless, the present results suggest that the CALUX bioassay could be a promising valid screening method for human blood plasma analyses. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailAutomated sample preparation-fractionation for the measurement of dioxins and related compounds in biological matrices: a review
Focant, Jean-François ULg; Pirard, Catherine; De Pauw, Edwin ULg

in Talanta (2004), 63(5), 1101-1113

This article reviews some of the recent developments in the extraction and clean-up areas of biological samples dedicated to dioxin and related compound analysis. A brief introduction on the major dioxin ... [more ▼]

This article reviews some of the recent developments in the extraction and clean-up areas of biological samples dedicated to dioxin and related compound analysis. A brief introduction on the major dioxin contamination events, which have occurred in the food chain, is given to illustrate the need of fast high throughput methods in case of crises. The emphasis of this paper is the method development based upon reliable instrumental extraction techniques for rapid sample processing and automation such as; supercritical fluid extraction (SFE), microwave-assisted extraction (MAE), pressurized liquid extraction (PLE) and, solid-phase extraction (SPE). The PLE and SPE are also discussed in conjunction with the use of a multi-column automated clean-up system that can accommodate up to 5 g of extracted lipids. The fractionation in sub-groups of analytes during the clean-up process allows the isolation of various types of toxicants from a single sample and illustrates the versatility of the system. An integrated extraction and clean-up instrument is finally presented in terms of feasibility and attainable sample turnover for the parallel processing of liquid and solid biological samples. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailMeasurement of PCDDs, PCDFs, and non-ortho-PCBs by comprehensive two-dimensional gas chromatography-isotope dilution time-of-flight mass spectrometry (GC x GC-IDTOFMS)
Focant, Jean-François ULg; Reiner, Eric J.; MacPherson, Karen et al

in Talanta (2004), 63(5), 1231-1240

Comprehensive two-dimensional gas chromatography with isotope-dilution time-of-flight mass spectrometry (GC x GC-IDTOFMS) was used to measure polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated ... [more ▼]

Comprehensive two-dimensional gas chromatography with isotope-dilution time-of-flight mass spectrometry (GC x GC-IDTOFMS) was used to measure polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF), and coplanar polychlorinated biphenyl (cPCB) concentrations in ash, sediment, vegetation, and fish samples. The GC x GC capability was achieved by using a quad jet, dual stage, thermal modulator. Zone compression of the GC peaks from modulation resulted in a significant increase of the signal intensity over classical GC-IDTOFMS. The GC x GC column set used an Rtx-Dioxin 2 phase as the first dimension (D-1) and an Rtx-500 as the second dimension (D-2). The chromatographic separation of the 17 PCDD/Fs and the 4 cPCBs was attained in D-1 except for 2,3,7,8-TCDD and CB126 for which deconvoluted ion currents (DIC) were required to be reported separately. The Rtx-500 phase separated the bulk matrix interfering compounds from the target analytes in D-2. The instrumental limit of detection (iLODs) was 0.5 pg for 2,3,7,8-TCDD. The calibration curves showed good correlation coefficients for all the compounds investigated in the concentration range of 0.5-200 pg. GC x GC-IDTOFMS results compared favorably to those from conventional isotope-dilution one-dimensional gas chromatography-high resolution mass spectrometry (GC-IDHRMS). The comprehensive mass analysis of the TOFMS further permitted the identification of other contaminants of concern in the samples. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailFT-IR measurement of tagitinin C after solvent extraction from Tithonia diversifolia
Ziemons, Eric ULg; Goffin, Eric ULg; Lejeune, Robert ULg et al

in Talanta (2004), 62(2), 383-387

Tagitinin C, an antiplasmodial compound, identified as one major compound of the subtropical medicinal plant, Tithonia diversifolia, was, determined by FT-IR spectroscopy method. The crude ether extracts ... [more ▼]

Tagitinin C, an antiplasmodial compound, identified as one major compound of the subtropical medicinal plant, Tithonia diversifolia, was, determined by FT-IR spectroscopy method. The crude ether extracts from aerial parts of the plant were evaporated to dryness and re-dissolved in tetrachloroethylene (C2Cl4) before analysis. The magnitude of the absorbance of the very specific C=O stretching vibration (v(c=o)) at 1664.8 cm(-1) was exploited in order to quantify tagitinin C. The determination coefficient (r(2)) of the calibration scale was 0.9994, the detection limit was lower than 3 mug ml(-1) and the quantification limit was lower than 10 mug ml(-1). Recovery values from 100.5 to 101.7% were found for spiked concentration levels from 19.91 to 89.95 mug ml(-1). The main characteristics of the curves obtained from the calibration standards and from the standard addition technique were not statistically different (Student t-test) suggesting that matrix effects were negligible. The results obtained for the determination of tagitinin C in the crude ether extract from aerial parts of T diversifolia by LC and FT-IR spectroscopic method agreed well: 0.76 +/- 0.02 and 0.773 +/- 0.009, of tagifinin C in dried plant respectively. (C) 2003 Elsevier B.V. All rights reserved. [less ▲]

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See detailDR-CALUX((R)) screening of food samples: evaluation of the quantitative approach to measure dioxin, furans and dioxin-like PCBs
Scippo, Marie-Louise ULg; Eppe, Gauthier ULg; De Pauw, Edwin ULg et al

in Talanta (2004), 63(5), 1193-1202

European legislation laid down maximum tolerable levels of dioxin in feed and food as well as analytical method requirements. In order to face with large monitoring programs, it was foreseen in the EU ... [more ▼]

European legislation laid down maximum tolerable levels of dioxin in feed and food as well as analytical method requirements. In order to face with large monitoring programs, it was foreseen in the EU strategy to integrate screening methods, using either a qualitative (screening) approach, or a quantitative approach. In this study, dioxin results obtained using the Dioxin Responsive Chemical-Activated LUciferase gene eXpression (DR-CALUX(R)) cell-based assay (quantitative approach), were compared with gas chromatography-high resolution mass spectrometry (GC-HRMS) analyses data. Instead of using World Health Organization-toxic equivalent factor (WHO-TEF), the comparison was based on the assessment of relative effective potencies (REPs) for each congener of the 17 toxic 2,3,7,8-polychlorodibenzo-p-dioxins/furans (PCDD/Fs) and 12 dioxin-like polychlorobiphenyls (DL-PCBs). According to published data, DR-CALUX(R)-REP evaluated here appear similar to WHO-TEF for PCDD/Fs while lower values were observed for DL-PCBs. We analyzed two "home made" contaminated fat samples, displaying both the same WHO-toxic equivalent quantities (WHO-TEQ) concentration (12 pg WHO-TEQ g(-1)). They were spiked with either a low or a high amount of DL-PCBs. In both cases, the DR-CALUX(R) measured concentration (picogram 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD) eq. g(-1)) corresponded to the PCDD/Fs WHO-TEQ concentration only. A good agreement was nevertheless found between the DR-CALUX(R) measurements and the recalculated DR-CALUX(R)-TEQ contents (using DR-CALUX(R)-REP instead of WHO-TEF), demonstrating that the observed response was due, in both cases, to the addition of the responses of the standards added to the fat. By contrast, in real contaminated samples (feed or cod liver samples), DR-CALUX(R) measured concentrations were similar to WHO-TEQ GC-HRMS measured concentrations. But, depending on the PCDD/Fs and DL-PCBs congener content, the DR-CALUX(R) measured concentrations were either lower or higher than calculated DR-CALUX(R)-TEQ contents, demonstrating that possible co-extracted contaminants contributed to the CALUX response. Owing to these divergences, the quantitative determination of dioxin-like content in food and feed using CALUX as screening method is questionable, except for samples displaying constant congener patterns, in which cases, correction factors could be applied. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailEvaluation of two commercial solid-phase microextraction fibres for the analysis of target aroma compounds in cooked beef meat
Machiels, D.; Istasse, Louis ULg

in Talanta (2003), 61(4), 529-537

The aroma profile of cooked beef meat has been investigated by solid-phase microextraction (SPME) combined with gas chromatography-mass spectrometry (GC-MS). Out of more than 200 volatile compounds, 36 ... [more ▼]

The aroma profile of cooked beef meat has been investigated by solid-phase microextraction (SPME) combined with gas chromatography-mass spectrometry (GC-MS). Out of more than 200 volatile compounds, 36 key odour-active compounds were selected for analysis. Several extraction times, desorption times, temperature conditions and fibre types were tested to achieve a fast and reproducible extraction, and a representative analysis of the aroma profile of cooked beef. Extraction conditions and fibre type significantly affected the majority of the target compounds. Divinylbenzene-carboxen-polydimethylsiloxane (DVB-CAR-PDMS) fibre presented a better reproducibility at all extraction times and extracted more efficiently the less volatile compounds than the carboxen-polydimethylsiloxane (CAR-PDMS) fibre. The high molecular weight compounds seemed to achieve faster the equilibrium between the headspace and DVB-CAR-PDMS fibre. The use of SPME was shown to be a simple, sensitive, selective, representative, fast, and low-cost method for the evaluation of key odour-active compounds in cooked beef meat, even if further research on quantitative analysis of volatiles using SPME on solid samples has to be done. (C) 2003 Elsevier B.V. All rights reserved. [less ▲]

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See detailGas chromatography-olfactometry analysis of the volatile compounds of two commercial Irish beef meats
Machiels, D.; van Ruth, S. M.; Posthumus, M. A. et al

in Talanta (2003), 60(4), 755-764

The volatile flavour compounds of two commercial Irish beef meats (labelled as conventional and organic) were evaluated by gas chromatography-olfactometry and were identified by gas chromatography-mass ... [more ▼]

The volatile flavour compounds of two commercial Irish beef meats (labelled as conventional and organic) were evaluated by gas chromatography-olfactometry and were identified by gas chromatography-mass spectrometry. The volatile compounds were isolated in a model mouth system. Gas chromatography-olfactometry was performed by a group of eight assessors using the detection frequency methodology. The odours of the detected compounds were described as well. Eighty-one volatile compounds were identified, 11 compounds of which possessed odour activity in the first beef sample and 14 of which in the second meat sample. Ten volatile flavour compounds were common to both: methanethiol, dimethyl sulphide, 2-butanone, ethyl acetate, 2- and 3-methylbutanal, an unknown compound, 2-octanone, decanal and benzothiazole. Two unknown compounds were only detected in the first sample while 2,3-pentanedione, 4-methyl-3-penten-2-one, 2-heptanone, dimethyl trisulphide and nonanal were only perceived in the second beef. Significant differences in terms of detection frequency, odour characteristics and in nature of the volatile flavour compounds were emphasised between the two samples. (C) 2003 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailAnalysis of 5-vinyl-1,3-oxazolidine-2-thione in complex matrices at ppb level
Mabon, N.; Wathelet, Jean-Paul ULg; Marlier, Michel

in Talanta (1999), 49(1), 199-206

5-Vinyl-1,3-oxazolidine-2-thione (5-VOT) is a goitrogenic compound released by enzymatic degradation of progoitrin, the most important glucosinolate occurring in rapeseed meal. This paper describes an ... [more ▼]

5-Vinyl-1,3-oxazolidine-2-thione (5-VOT) is a goitrogenic compound released by enzymatic degradation of progoitrin, the most important glucosinolate occurring in rapeseed meal. This paper describes an analytical method for determining the 5-VOT in complex matrices. The method proposed by Quinsac et al. [J. Assoc. Off. Anal. Chem., 75(3) (1992) 529] has been improved by modification of the extraction conditions and the purification steps. The extraction of 5-VOT is performed with hot acid buffer. The first purification step is achieved by solid-phase chromatography (C-18). The second purification step of 5-VOT is carried out by complexation with phenyl mercury acetate in cyclohexane and, afterwards, by decomplexation using an aqueous solution of sodium thiosulfate. These reactions move 5-VOT from an aqueous to an organic medium, and then back again to the aqueous phase. This Procedure ensures a high purification efficiency. The precise quantification of 5-VOT is completed in 12 min by reverse-phase liquid chromatography (C18), using an isocratic elution with an ultraviolet detector and with synthetic 4,4-dimethyl-1,3-oxazolidine-2-thione as internal standard. Using this modified method, 5-VOT can be determined in different matrices such as rapeseed meal, animal diets, muscle, several organs (thyroid, liver, kidney and lung) and biological fluids (plasma and milk). The quantification limit of 5-VOT in the sample is of 1 ppb (1 mu g kg(-1)), the recovery rate of 5-VOT is about 90% and the repeatability is over 97%. (C) 1999 Elsevier Science B.V. All rights reserved. [less ▲]

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