Biomedical subjects

R D Josephs

Publications and source records attributed to R D Josephs.

4 recordsLinked to original sources

PubMed2004

Trichothecenes: reference materials and method validation.

The frequent contamination of food and feed with trichothecene mycotoxins, the high consumption of these products, and the potential risk associated herewith, has led to an increasing public awareness and therefore to the establishment of measures to control trichothecene contamination. The analytical difficulty and the economic importance of controlling trichothecenes in food and feed support the need for certified reference materials (CRMs) and validated methods. They form invaluable tools to ensure comparability and traceability in analytical measurements and are very useful for the implementation of written standards, legislation/regulations and laboratory accreditation. The present paper provides an overview of previous work, current strategies and prospectives for the production of CRMs and validation of analytical methods in the field of trichothecene analysis. Additional information is given on methodological demands, normative frameworks and commonly accepted procedures.

Chemistry Techniques, Analytical↗

PubMed2003

Zearalenone in maize: stability testing and matrix characterisation of a certified reference material.

Within the certification process of a reference material for the determination of the mycotoxin zearalenone (ZON) in maize, short- and long-time stability tests of naturally contaminated maize have been performed. The short-term stability of ZON in the maize was evaluated under four different conditions (4, 25, 40 and 70 degrees C) in preliminary studies. Four storage times of 0, 1, 2 and 4 weeks were investigated using HPLC. The long-term stability study was conducted with measurements after 0, 3, 6, 12, 24 and 36 months under three storage conditions (4, 25 and 40 degrees C) in preliminary studies using HPLC. Stability data gained under two different conditions (4 and 25 degrees C) with five storage times of 0, 1, 6, 12 and 18 months were further evaluated for the contaminated maize in the certification process. Before the certification, the maize matrix had been characterized with respect to dry residue, ash content, fat content, protein content, ergosterol content and total dietary fibre, and the efficiency of gamma-irradiation on the fungal flora was investigated. The stability of the maize matrix was evaluated by monitoring UV absorption and ergosterol content under four different storage conditions (4, 25, 35 and 70 degrees C) with five storage times of 0, 1, 6, 12 and 24 months. Other possibly occurring mycotoxins (deoxynivalenol, nivalenol, 3-acetyl deoxynivalenol, 15-acetyl deoxynivalenol, fusarenon X and moniliformin) have been quantified. On the basis of the stability measurements, which showed no significant trends for both short- and long-term stabilities, it can be recommended to store the samples at temperatures < 4 degrees C and ship the samples at ambient temperatures.

Chromatography, High Pressure Liquid↗

PubMed2001

International interlaboratory study for the determination of the Fusarium mycotoxins zearalenone and deoxynivalenol in agricultural commodities.

Twenty-eight laboratories from 12 different countries participated in an interlaboratory study for the determination of the Fusarium mycotoxin zearalenone (ZON) in maize and deoxynivalenol (DON) in maize and wheat employing their usual in-house methods. The aim of this study was to obtain information about the state-of-the-art of ZON and DON analysis in cereals and to support a knowledge and experience exchange between the participating laboratories in the field of mycotoxin analysis. Eight different sample types were distributed to the participants, 'blank' materials, spiked samples (102 microg/kg ZON in maize and 475 microg/kg DON in wheat) and naturally-contaminated maize and wheat. For the final separation and quantification either gas chromatography (GC), high performance liquid chromatography (HPLC), thin layer chromatography (TLC) or enzyme linked immunosorbent assays (ELISA) were employed by the participating laboratories. Coefficients of variation (CV) between laboratory mean results (outliers rejected) ranged from 28 to 41% for ZON and from 32 to 38% for DON. The results are close to the between laboratory CV criteria of 40% for DON and ZON at concentration levels of >100 microg/kg established by the CEN in 1999. A good trueness was obtained for the wheat samples spiked at 475 microg/kg DON. However, a significant deviation at p = 0.01 from the respective target value was observed for the maize samples spiked at 102 microg/kg ZON. The high CVs can be traced back to problems occurring by determination of the concentration of the participants' own calibrant solutions. Additionally, the variability of the results is strongly influenced by the use of different final separation and quantification procedures.

Calibration↗

PubMed1998

Determination of trichothecene mycotoxins in wheat by use of supercritical fluid extraction and high-performance liquid chromatography with diode array detection or gas chromatography with electron capture detection.

The extraction behaviour of the Fusarium mycotoxin deoxynivalenol (DON) and some related type B trichothecenes from spiked seasand, spiked wheat flour and naturally contaminated wheat flour with modified supercritical CO2 has been investigated and optimized under several conditions. The extraction fluid was decompressed over a solid-phase trap and the amount of deposited analytes was determined by HPLC-diode array detection (DAD) or GC-electron capture detection (ECD) without any further clean-up. Recovery rates as high as 90.1 +/- 10.7% were achieved for spiked wheat samples and 53.0 +/- 3.2% for naturally contaminated samples. The performance of the optimized supercritical fluid extraction (SFE) method was compared with an already well established analytical method employing extraction on a rotary shaker in combination with Mycosep clean-up. Moreover, the SFE procedure developed for naturally DON contaminated wheat was employed for the simultaneous extraction of 5 type B trichothecenes by GC-ECD. This work represents the first successful approach in obtaining an SFE-method for the extraction of Fusarium mycotoxins from wheat with reasonable recoveries and good precision.

Chromatography, Gas↗