showing 13 related works from this author
Occurrence of fumonisins B1 and B2 in broa, typical Portuguese maize bread
2007
Fumonisin B1 (FB1) and fumonisin B2 (FB2) are mycotoxins mainly produced by Fusarium verticillioides, and Fusarium proliferatum, fungi species most commonly isolated from maize. The natural occurrence of FB1 and FB2 in broa, typical Portuguese maize bread, was evaluated in 30 samples. Twenty five were found positive with levels ranging from 142 to 550 [mu]g kg- 1. The limit established by the European regulations was exceeded by 27% of the samples. The tolerable daily intake for fumonisin B1, and B2, alone or in combination, for all of the analysed samples, was lower than 2 [mu]g kg- 1 body weight per day established by the European Commission. http://www.sciencedirect.com/science/article/B…
Ochratoxin A in the morning and afternoon portions of urine from Coimbra and Valencian populations.
2008
Abstract The widespread contamination of foodstuffs and beverages by mycotoxins, such as ochratoxin A (OTA), has made the monitoring of human contamination levels essential. By using a sensitive, accurate and speedy method that combines extraction with 5% NaHCO 3 , immunoaffinity column clean-up and HPLC with fluorescence detection, the human exposure to OTA through urine analysis can be monitored. This method is less invasive than blood monitoring and has the potential to be a good marker of human exposure. The limit of quantification of the method was 0.007 ng/mL of urine, with recoveries of OTA, from urine samples spiked at levels between 0.02 and 0.1 ng/mL, higher than 91% with RSD lowe…
Evaluation of enniatins A, A1, B, B1 and beauvericin in Portuguese cereal-based foods.
2012
Sixty-one samples of Portuguese cereal-based foods were analysed for the occurrence of emerging mycotoxins called enniatins (A, A1, B and B1) and beauvericin. Samples were extracted with a mixture of acetonitrile/water (85/15, v/v) using an Ultra-Turrax homogeniser, and mycotoxins were detected with liquid chromatography coupled to a mass spectrometer. This method was validated and adequate values of recovery (70-103%) and relative standard deviation (15%) were obtained. Signal suppression/enhancement was studied and matrix-matched calibration used to minimise this effect, but no additional clean-up step was necessary. The mass spectrometer was operated in selected reaction monitoring (SRM)…
Levels of ochratoxin A in wheat and maize bread from the central zone of Portugal.
2007
Ochratoxigenic fungi are natural contaminants of cereal and the produced toxins are harmful to humans and animals. Ochratoxin A (OTA) is among the most important mycotoxins, and the International Agency for Research on Cancer (IARC) classifies it as possibly carcinogenic to humans (group 2B). A total of 61 samples of bread from the central zone of Portugal were analysed for OTA by liquid chromatography (LC) with fluorescence detection (FD). For confirmation two procedures were applied, methyl ester derivatization with boron trifluoride-methanol and liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI/MS/MS). As far as we know, this is the first report where on-line…
Comparison of three solid-phase extraction processes in quantification of ciprofloxacin and enrofloxacin in pork meat
2012
Due to strong implications for food safety, control of fluoroquinolones residues in swine meat should be undertaken to verify compliance of the contamination levels with the maximum residue limits recently updated by Commission Regulation (EU) No. 37/2010 of 22 December 2009. Solid-phase extraction is widely used in antibiotic analysis in food of animal origin. In this study, the results of a comparative study using different types of solid-phase extraction columns, HLB, MCX, and MAX, for ciprofloxacin and enrofloxacin analysis, in pork meat, are presented. In addition, diverse sample treatments for defatting, precipitate proteins, eliminate cations, and increase the ionic strength, were us…
Analysis of fumonisins in corn-based food by liquid chromatography with fluorescence and mass spectrometry detectors
2008
Abstract The presented procedure involves an extraction with methanol–water, centrifugation and cleanup with immunoaffinity columns. A comparison study between fluorescence detector, mass spectrometry, and tandem mass spectrometry with a triple quadrupole (QqQ) analyzer using an electrospray ionisation interface for the determination of fumonisin B1 and B2 in corn-based products has been performed. Limits of quantification obtained by the three detectors were lower than the maximum levels established by European Commission. Liquid chromatography coupled to tandem mass spectrometry provides higher sensitivity (12 μg kg−1for fumonisins B1 and B2) when compared to mass spectrometry (40 μg kg−1…
Determination of ochratoxin A in maize bread samples by LC with fluorescence detection.
2007
Ochratoxin A (OTA) is a secondary fungal metabolite produced by several moulds, mainly by Aspergillus ochraceus, A. carbonarius, A. niger and by Penicillium verrucosum. The present work shows the results of comparative studies using different procedures for the analysis of OTA in maize bread samples. The studied analytical methods involved extraction with different volumes of PBS/methanol, different extraction apparatus, and clean-up through immunoaffinity columns. The separation and identification were carried out by high-performance liquid chromatography with fluorescence detection. The optimized method for analysis of OTA in maize bread involved extraction with PBS:methanol (50:50), and …
Determination of organochlorine pesticide residues in honey from the central zone of Portugal and the Valencian community of Spain
2004
In this study nine organochlorine pesticide residues ([alpha]-, [beta]-, and [gamma]-hexachlorocyclohexane (HCH), hexachlorobenzene (HCB), aldrin, p,p'-DDE, p,p'-DDD, o,p'-DDT, and p,p'-DDT) in forty nine samples of honey collected from markets of Portugal and Spain during 2001 and 2002, respectively, were evaluated. For this evaluation, three analytical procedures were studied. The analytical procedure, based on LLE extraction with ethyl acetate followed by gas chromatography-electron-capture detection (GC-ECD) for quantification, and mass spectrometry (GC-MS) for confirmation, has been selected. Recoveries of spiked samples ranged from 68%, for [beta]-HCH, and 126% for p,p'-DDT, for forti…
Photo-induced fluorescence of magnesium derivatives of tetracycline antibiotics in wastewater samples
2009
Abstract An analytical strategy, for the determination of tetracyclines (TCs), based on a HPLC system coupled with a photo-reactor followed by post-column derivatization was developed. Higher fluorescence emission after coupling the resulting photo-fragments with magnesium ions was observed for the determination of minocycline (MC), epitetracycline (ETC), tetracycline (TC) and doxycycline (DC). The manifold included a HPLC system with a photo-reactor (PTFE tubing helically coiled around a low-pressure mercury lamp), a mixing T-piece and a fluorescence detector. The derivatization reagent was delivered at 0.5 mL min −1 by a pump. After HPLC separation using a gradient system with a mobile ph…
Occurrence and risk assessment of zearalenone in flours from Portuguese and Dutch markets
2014
The occurrence of zearalenone (ZEA) in different flours for human consumption, from the Portuguese and Dutch markets, was evaluated. Good analytical performance was obtained through extraction with acetonitrile:water (90:10), clean-up with immunoaffinity columns, and detection and quantification by liquid chromatography-fluorescence detection. ZEA levels were determined in 48 samples to verify the compliance with the maximum permitted levels by European legislation. Two flour samples from Portugal exceeded the maximum limit established by EC. A major presence and levels in maize flours was shown. Coimbra (Portugal) and Utrecht (The Netherlands) samples showed that 37.5% of the samples were …
Assessment of Pesticide Residues in Honey Samples from Portugal and Spain
2003
Fifty samples of honey collected from local markets of Portugal and Spain during year 2002 were analyzed for 42 organochlorine, carbamate, and organophosphorus pesticide residues. An analytical procedure based on solid-phase extraction with octadecyl sorbent followed by gas chromatography-mass spectrometry (GC-MS), for organochlorines, and by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS), for organophosphorus and carbamates, has been developed. Recoveries of spiked samples ranged from 73 to 98%, except for dimethoate (40%), with relative standard deviations from 3 to16% in terms of repeatability, and from 6 to 19% in terms of reproducibility. …
Determination of ochratoxin A in organic and non-organic cereals and cereal products from Spain and Portugal
2008
The objective of this work was to know the occurrence of OTA in organic and non-organic cereals and cereal products from Spain and Portugal. A method based on extraction with matrix solid phase dispersion (MSPD) using octylsilica (C8) followed by liquid chromatography coupled with fluorescence detection (LC-FD) was used to determine OTA from the selected samples. Recoveries of OTA from the studied samples spiked at 10 ng/g level ranged from 78% to 89% with a standard deviation of 3.66. The limits of detection and quantification of this method were 0.05 and 0.19 ng/g, respectively. Furthermore, LC-FD after OTA methylation was used to confirm the identity of OTA in all positive samples. This …
Occurrence of fumonisins B1 and B2 in Portuguese maize and maize-based foods intended for human consumption.
2007
Fumonisin B(1) (FB(1)) and fumonisin B(2) (FB(2)) are mycotoxins mainly produced by Fusarium verticillioides and Fusarium proliferatum, which are field pathogens of maize. A survey was conducted on the incidences of FB(1) and FB(2) in both maize and derived products purchased in Portugal. The analytical method involved extraction with methanol-water, clean-up by immunoaffinity column and derivatization with naphthalene-2,3-dicarboxaldehyde. Determination was carried out by high-performance liquid chromatography (HPLC) with spectrofluorimetric detection, with liquid chromatography/mass spectrometry (LC/MS) confirmation. The presence of FB(1) and FB(2) was determined in 67 samples of maize an…