Biomedical subjects

C A Fente

Publications and source records attributed to C A Fente.

14 recordsLinked to original sources

PubMed2003

Development of a method for direct visual determination of aflatoxin production by colonies of the Aspergillus flavus group.

This report describes a simple, rapid and reliable method for screening the aflatoxin production by moulds of the Aspergillus flavus group. Strains were cultivated on yeast extract agar to which methylated beta-cyclodextrin derivative plus sodium desoxycholate was added. Production of aflatoxins was readily detectable by direct visualisation of a beige ring surrounding colonies after an incubation time of 3 days at 28 degrees C. When this ring was examined under UV light, it exhibited blue fluorescence. The presence of aflatoxins was confirmed by extracting the medium with chloroform and examining the extracts by HPLC with fluorescence detection.

Aflatoxins↗

PubMed2003

Application of a modified culture medium for the simultaneous counting of molds and yeasts and detection of aflatoxigenic strains of Aspergillus flavus and Aspergillus parasiticus.

Molds and yeasts from 91 samples of feed and raw materials used in feed formulation were enumerated on a new culture medium to which a beta cyclodextrin (beta-W7M 1.8-cyclodextrin) had been added. This medium was compared with other media normally used in laboratories for the routine analysis of fungi, such as Sabouraud agar, malt agar supplemented with 2% dextrose, and potato dextrose agar. When a t test for paired data (0.05 significance level, 95% confidence interval) was applied, no statistically significant differences between the results obtained with the new culture medium and those obtained with the other media used to enumerate molds and yeasts were found. For the evaluation of contamination due to aflatoxin for all of the samples, Sabouraud agar and yeast extract agar, both supplemented with 0.3% beta-W7M 1.8-cyclodextrin, and APA (aflatoxin-producing ability) medium were used. Aflatoxin was detected in 21% of the feed samples and in 23% of the raw-material samples analyzed, with maximal amounts of 2.8 and 6.0 microg of aflatoxin B1 per kg, respectively, being detected. In any case, the aflatoxin contents found exceeded the legally stipulated limits. The t test for paired data (0.05 significance level, 95% confidence interval) did not show statistically significant differences between the results obtained with the different culture media used for the detection of aflatoxins. The advantage of the new medium developed (Sabouraud agar with 0.3% beta-W7M 1.8-cyclodextrin) is that it allows simultaneous fungal enumeration and determination (under UV light) of the presence of aflatoxin-producing strains without prior isolation and culture procedures involving expensive and/or complex specific media and thus saves work, time, and money.

Aflatoxins↗

PubMed2002

Gas chromatography-tandem mass spectrometry determination of 17alpha-ethinylestradiol residue in the hair of cattle. Application to treated animals.

A gas chromatography-tandem mass spectrometry (GC-MS(2)) method for the detection and quantification of 17alpha-ethinylestradiol in the hair of cattle has been developed, and uses an ion trap analyzer. After the digestion of 500 mg of hair by alkaline digestion using 1 M NaOH, extraction and purification of the steroid were performed in the same step by means of diphasic dialysis. This technique is a semipermeable-membrane technology developed for the direct extraction of relatively low-molecular-mass analytes. The process was performed by employing acetate buffer to homogenize the digested hair, dichloromethane as the extraction solvent at 37 degrees C, and stirring at 150 rpm for 4 h. The recovery was between 74 and 94%. The detection limit was 0.52 ng/g in hair. To evaluate the validity of the methodology, five animals, approximately 3 months old, received an intramuscular anabolic dose of the drug. The xenobiotic could be detected 7 or 14 days after the treatment (between 2.01 and 23.61 ng/g), and until the end of the study (day 98). No statistical difference between hair color and hair assay outcomes was found.

Animals↗

PubMed2002

Development of a diphasic dialysis method for the extraction/purification of residues of ethinylestradiol in hair of cattle, and determination by gas chromatography-tandem mass spectrometry.

A confirmatory method for the analysis of ethinylestradiol extracted from cattle hair was developed. After the extraction of the xenobiotic from the hair, by using alkaline digestion, the purification of the extract was carried out by employing diphasic dialysis. For the optimization of the technique several parameters was evaluated such as pH, extraction solvents, temperatures, times and agitation speeds. The detection and confirmation of the steroid was accomplished by using a GC-MS2 ion trap system after trimethylsilylation. The calibration curve was linear over the range of 4-20 ng/g. The detection and quantification limit were 0.52 and 0.80 ng/g respectively; with recoveries up to 94%.

Animals↗

PubMed2001

New additive for culture media for rapid identification of aflatoxin-producing Aspergillus strains.

A new reliable, fast, and simple method for the detection of aflatoxigenic Aspergillus strains, consisting of the addition of a cyclodextrin (a methylated beta-cyclodextrin derivative) to common media used for testing mycotoxin production ability, was developed. We propose the use of this compound as an additive for fungal culture media to enhance the natural fluorescence of aflatoxins. The production of aflatoxins coincided with the presence of a bright blue or blue-green fluorescent area surrounding colonies when observed under long-wavelength (365-nm) UV light after 3 days of incubation at 28 degrees C. The presence of aflatoxins was confirmed by extracting the medium with chloroform and examining the extracts by high-pressure liquid chromatography with fluorescence detection.

Aflatoxins↗

PubMed2000

Application of the assay of aflatoxins by liquid chromatography with fluorescence detection in food analysis.

HPLC using fluorescence detection has already become the most accepted method for the determination of aflatoxins due to its several advantages over other analytical methods. Both normal- and reversed-phase HPLC can be used. However the reversed-phase HPLC methods are more popular. Liquid chromatographic determination of aflatoxins using fluorescence detection and its application in food analysis is reviewed in this article.

Aflatoxins↗

PubMed2000

Determination of quinolones in animal tissues and eggs by high-performance liquid chromatography with photodiode-array detection.

A rapid, specific reversed-phase HPLC method is described, with solid-phase extraction, for assaying five quinolones (ciprofloxacin, difloxacin, enrofloxacin, norfloxacin and marbofloxacin) with confirmative diode-array detection in samples of bovine kidney, muscle and eggs. The least efficient extraction was marbofloxacin from kidney tissue (64%). The lower detection limit for each quinolone was: enrofloxacin and ciprofloxacin, 1 ng; norfloxacin and difloxacin, 2 ng; marbofloxacin, 4 ng injected. The intra-day relative standard deviations were lower than 7.9% and lower than 8.6% for inter-day assays. These results indicate that the developed method had an acceptable precision.

4-Quinolones↗

PubMed1999

Determination of clenbuterol residues in bovine hair by using diphasic dialysis and gas chromatography-mass spectrometry.

A method for the determination of clenbuterol (4-amino-3,5-dichloro-alpha[(tert.-butylamino)methyl]-benzyl alcohol hydrochloride) in hair of living cows has been developed. Hair samples were digested in an alkaline medium. The diphasic dialysis technique is a semi-permeable membrane technology developed for the direct extraction of relatively low-molecular-mass analytes such as clenbuterol. In this case, we used sodium citrate buffer to homogenize the digested hair, dichloromethane was used as the extraction solvent at 37 degrees C, and stirring was applied at 150 rpm for 4 h. The analysis was carried out using gas chromatography-mass spectrometry. The calibration curve for clenbuterol in hair was linear in the range from 12.5 to 400 ng g(-1). The detection limit of clenbuterol was 5 ng g(-1) and the quantification limit was 12.5 ng g(-1), in hair. A good inter-day reproducibility was obtained (R.S.D. = 7.08%). The repeatability and intra-day reproducibility (50 ng g(-1) of hair, n = 10) show R.S.D.s of 7.1 and 9.5%, respectively.

Animals↗

PubMed1999

Determination of dexamethasone in bovine liver by chemiluminescence high-performance liquid chromatography.

A new method for the determination of dexamethasone (9alpha-fluoro-11beta,17alpha,21-trihydroxy-16alpha -methylpregna-1, 4-diene-3,20-dione) in bovine liver was developed. This new liquid-liquid extraction method comprises the addition of sodium hydroxide to the tissue sample followed by extraction with ethyl acetate. After centrifugation, the extract is evaporated to dryness and the residue dissolved in acetonitrile. The cleaning of the fat is performed with n-hexane, and the acetonitrile layer is evaporated. Analysis of the extracts is performed using high-performance liquid chromatography with chemiluminescence detection employing luminol as CL reagent. A series of recovery curves performed at spiking levels of 50, 30, 10, 5, and 2.5 ppb show that at least 80% of DEX can be recovered from liver and that the chemiluminescence detection yields satisfactory results with respect to sensitivity (LOD 0.2 ppb), reproducibility (CV% 10.7) and repeatability (CV% 6.2-8.9).

Animals↗

PubMed1998

Interaction between cyclodextrins and aflatoxins Q1, M1 and P1. Fluorescence and chromatographic studies.

The fluorescence properties of the aflatoxins M1, Q1, P1 in solution and the effect of various cyclodextrins (alpha-, beta-, gamma-, hydroxypropyl-beta- and alpha-beta-heptakis-di-O-methyl-beta-) on their fluorescence emission were studied. Among the aflatoxins, a substantial enhancement of the fluorescence emission of aflatoxin Q1 in the presence of aqueous solutions of alpha-, beta-, hydroxypropyl-beta, and alpha-beta-heptakis-di-O-methyl-beta-cyclodextrin, was observed. On the contrary, gamma-cyclodextrin proved to be inefficient to enhance the fluorescence properties of this compound. No important fluorescence enhancement was found for aflatoxins P1 or M1 for any of the cyclodextrin derivatives tested. The complex formation constant (Kf) of these compounds with beta-cyclodextrin was chromatographically determined, and from the results obtained, we can conclude that Kf cannot be used alone to explain the fluorescence increase. Thermodynamic studies showed that delta-H and delta-S parameters, associated with the partition of aflatoxins in RP-HPLC, increased when beta-cyclodextrin was added to the eluent.

Aflatoxin M1↗

PubMed1998

Determination of alternariol in tomato paste using solid phase extraction and high-performance liquid chromatography with fluorescence detection.

Alternaria spp. produce a wide variety of toxic metabolites with different chemical structures. Tomato products have been considered a likely source of Alternaria toxins in the human diet because Alternaria is an important spoilage mold of tomatoes. A new method for the determination of these mycotoxins in tomato paste, involving solid phase cartridges for extraction before HPLC fluorescence detection with a reversed phase column and isocratic elution, was developed. The method was demonstrated to be linear in the range 5.2-196 ppb of alternariol (AOH) in tomato paste. Good recoveries were obtained for AOH at all levels assayed (minimum 77.2%). The detection limit of the AOH toxin in real samples of tomato paste was low, 1.93 ppb. The precision of the method was demonstrated with a good repeatability (RSD = 2.98%) and reproducibility (RSD = 9.35%).

Calibration↗

PubMed1997

Determination of residues of the beta-agonist clenbuterol in liver of medicated farm animals by gas chromatography-mass spectrometry using diphasic dialysis as an extraction procedure.

A method has been developed for the rapid confirmation of clenbuterol in cow liver using gas chromatography coupled with detection by mass spectrometry of the trimethylsilyl derivatives of clenbuterol. The technique used for the extraction was diphasic dialysis. It was observed that the best suitable solution to homogenize the liver the barium hydroxide-barium chloride buffer, the optimal extraction solvent was tert.-butylmethyl ether at an extraction temperature of 37 degrees C, and stirring should be applied at 150 rpm for 4 h. This extraction method improves clenbuterol recovery up to values of 99.3%. With the use of the barium buffer, derivatization is performed more efficiently and the detection and quantification limits can be decreased to values close to 250 ppt and 500 ppt, respectively.

Adrenergic beta-Agonists↗

PubMed1996

Simple and sensitive high-performance liquid chromatography--fluorescence method for the determination of citrinin application to the analysis of fungal cultures and cheese extracts.

A new and highly sensitive method for the detection of the important mycotoxin, citrinin, has been developed. Spectroscopic studies demonstrate that the fluorescence of this metabolite is influenced by the pH of the environment. This fact was exploited in the chromatographic determination of citrinin with fluorescence detection. The proposed method, based on the addition of 1 M hydrochloric acid as an acidic post-column reagent, has a limit of detection of 0.9 center dot 10(-7) M. Analytical validation shows that linearity can be assumed from 2 center dot 10(-7) to 10(-4) M citrinin. The repeatability and reproducibility are satisfactory, with R.S.D. = 5.1% (n = 9, c = 10(-5) M) and R.S.D. = 7.2% (n = 9, c = 10(-5) M). The method was also applied to the determination of this mycotoxin produced by mould cultures isolated from soft cheese and also from soft cheese and also from cheese extracts spiked with citrinin. The specificity of the method is demonstrated and the necessity for post-column acidification is illustrated on real samples.

Cheese↗

PubMed1996

Postcolumn excitation of aflatoxins using cyclodextrins in liquid chromatography for food analysis.

Measurement of fluorescence increase was used for the comparative quantification of the effect that several cyclodextrins (alpha-, beta-, heptakis-2,6-beta-omicron-dimethyl- and gamma-) produce on the fluorescent response of aflatoxins B1 and G1. This constitutes a new chromatographic method with stability of the mobile phase, and shows general improvements in the chromatographic conditions with respect to other methods (especially those using an iodine reservoir as a postcolumn reactor). A C18-type column was used, with methanol-water (60:40, v/v) as the mobile phase. The excitation phase of the natural fluorescence of aflatoxins, a 10(-2) M solution of each cyclodextrin, was introduced postcolumn. The determination of the elution order aflatoxin G2 > G1 > B2 > B1 was performed for each phase in less than 15 min. As expected using an aqueous-alcoholic medium, an increase in the fluorescence response of aflatoxins with an unsaturated furanic ring was found to occur with all the cyclodextrins studied, except gamma-cyclodextrin. The observed increase was larger for heptakis-2,6-beta-omicron-dimethyl- than for beta-cyclodextrin (to our knowledge, the only cyclodextrin previously described in the literature to serve for the determination of aflatoxins). The difference is of the order of 70.1-fold in the case of aflatoxin G1 and 45.2-fold in the case of aflatoxin B1. The detection limit in the mobile phase used was determined (for aflatoxin B1) for beta-cyclodextrin and 2,6-beta-omicron-dimethylcyclodextrin (signal-to-noise ratio 1:3) to be 4 and 9 mg 1(-1), respectively.

Aflatoxin B1↗