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Due to the utilisation of 1,1,2-trichlorotrifluoroethane (CFE) as extraction solvent the IR-spectrometric determination of total petrol hydrocarbon (TPH) in soil according to ISO/TR 11046 has been replaced by gas chromatography/flame ionisation detection (GC/FID) after extraction with a halogen-free solvent according to ISO/DIS 16703:2001. The results obtained with both methods by field laboratories in three proficiency testing (PT) rounds are compared. The consensus means obtained with GC/FID are typically 10%-20% (ranging between 0% and 25%) higher than those found with IR-spectroscopy. On the contrary, coefficients of variation (CV) are roughly double in case of GC/FID and are briefly discussed against the background of the Horwitz equation.
A procedure for the quantification of the PCB marker congeners 28, 52, 101, 138, 153, 180 in plastic waste form the recycling of cables in the range of content between 0.1 mg kg-1 and 20 mg kg-1 was validated. Representative reference materials for laboratory analyses were produced using granulates from different recycling processes. The method development included aspects of grinding, sieving, homogenising as well as the comparison of extraction methods and chromatographic conditions. The validated procedure foresees grinding of the technical sample to an upper particle size limit of 0.50 mm followed by extraction with an unpolar solvent such as n-hexane and gas chromatographic determination. LOD and LOQ for individual congeners ranged between 0.01 mg kg-1 and 0.08 mg kg-1. Electron capture detection (ECD) and mass selective detection (MS) were equivalent if chromatographic conditions were appropriately selected. The application of MS was advantageous in presence of significant amounts of interfering components which have been found in some cables.
Three reference materials containing the marker congeners in the range of 0.1 mg kg-15 mg kg-1 were submitted to a final validation intercomparison with 23 selected field laboratories using the developed method. Relative reproducibility standard deviations varied between 15% and 33%.
The 2-year international joint project HYCREF (Contract-No. G6RD-CT-2002-00854), funded by the European Commission in the 5th Framework programme, aimed to develop methods to prepare homogenous and stable water-, soil- and waste reference materials contaminated with mineral oil hydrocarbons and to test certify the mineral oil content by gas chromatographic methods. As mineral oil products are important sources for environmental contaminations, appropriate reference materials certified by using the new gas chromatographic methods (soil: ISO/FDIS 16703, waste: prEN 14039 and KW/04, water: ISO 9377-2) are highly needed. Additional to the HYCREF-results presented in part Imineral contaminated soilsthis second paper gives an overview of the feasibility study for the preparation and test certification of three waste reference materials (offshore marine sediment, building material and industrial waste). The following specifications, which had been defined in the project work plan, were reached successfully: uncertainty of the mineral oil content resulting from the certification exercise ≤ 5% and a between-bottle inhomogeneity of ≤ 3%. All three materials have been evaluated for long- and short term stability. They contain different levels and types of mineral oil and cover the full application range of ISO/FDIS 16703 and prEN 14039 (10010,000 mg/kg). The expanded uncertainties U cert of the three materials are about 6%. In this way, they are comparable to ERM®-CC015a (U cert=7.1%, mineral oil in a river sediment) and are suited to close the present gap of commercially available CRM for mineral oil determination in waste.
The aim of this study was to investigate the distribution of zearalenone in wheat kernels contaminated with this mycotoxin. Kernels from a sample of a wheat harvest affected by Fusarium culmorum were sorted into six groups according to their visual attributes. Milled portions of these groups were analysed by high-performance liquid chromatography with fluorescence and diode array detection. The clean-up was performed with an immunoaffinity column after methanol/water (4:1, v/v) extraction. The zearalenone content of the unsorted kernel fraction was 74 µg/kg. The group of healthy-looking kernels was contaminated with only 6 µg/kg of zearalenone. The groups of kernels that appeared shrunken and chalky white, damage routinely caused by Fusarium, were contaminated with 170 and 117 µg/kg, respectively. A remarkably high level of zearalenone contamination, 2,184 µg/kg, was observed for the group of reddish kernels. An association between the presence of the red pigment aurofusarin and high levels of zearalenone was found. Therefore, this pigment may be used as a marker of high zearalenone content.
Distribution of Trichothecenes, Zearalenone, and Ergosterol in a Fractionated Wheat Harvest Lot
(2008)
To investigate possible co-occurrences of type B trichothecenes and zearalenone within a Fusarium culmorum-infected wheat harvest lot, kernels were fractionated into six groups by visual criteria. The Fusarium-damaged kernels were subdivided into white, shrunken, and red kernel groups, and the remaining kernels were sorted into healthy, black spotted, and nonspecific groups. The distribution patterns of nivalenol, deoxynivalenol, zearalenone, and ergosterol were determined for possible correlations. Significant correlations between the distribution patterns were found for the mycotoxins and ergosterol for the grouped kernels (r = 0.997-0.999, p < 0.0001). Additionally, remarkably outstanding levels of nivalenol (24-fold more than the mean at 1.16 mg/kg), deoxynivalenol (27-fold more than the mean at 0.16 mg/kg), zearalenone (25-fold more than the mean at 77 µg/kg), and ergosterol (17-fold more than the mean at 13.4 mg/kg) were found in the red kernel group. Further, detailed mycotoxin and ergosterol analyses were carried out on various segments (kernel surface, conidia, bran, and flour) of the red kernels. However, the mycotoxin and ergosterol distribution profiles revealed nonsignificant correlations for these kernel segments, with the exception of deoxynivalenol and nivalenol, which were moderately correlated (r = 0.948, p = 0.035).
High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) can be used for simultaneous quantification of various mycotoxins in contaminated food samples. Therefore, multi-mycotoxin methods have been developed in the last couple of years. To enlarge these methods for further analytes, we have developed a LC-MS/MS method for the quantification of the mycotoxin aurofusarin. Additionally, further LC-MSn experiments were performed to demonstrate the fragmentation pattern of aurofusarin. Applicable multiple reaction monitoring (MRM) transitions of aurofusarin were found and optimized by parameter variation of the tandem mass spectrometer. The applicability of the developed method was tested by analysis of naturally contaminated wheat.
Liquid chromatography coupled with tandem mass spectrometric detection has gained more importance for mycotoxin determination in recent years. In addition to instrumental improvements, the development of LC-MS-MS has also been a consequence of the availability of stable isotope internal standards, e.g., 13C-labelled mycotoxins. Thus, the LC-ESI-MS-MS method using a 13C15-deoxynivalenol internal standard as a state-of-the-art technique was selected as a reference procedure for an in-house method comparison study of the determination of deoxynivalenol (DON) in wheat materials. Alternative methods include LC-diode array detection, which is a frequently used routine procedure for DON-analysis, and gas chromatography after trimethylsilylation. For GC application, an electron capture detector and a negative chemical ionisation mass spectrometry detector were used, which have both been well described in the literature. The method comparison was conducted using t test statistics. Additionally, this study also calculates important method performance characteristics, including accuracy, linearity, limit of detection, limit of quantification, recovery, and variation coefficient. Furthermore, this is the first report of a GC-MS method for the determination of DON using a fully carbon-labelled 13C15-DON as an IS. The GC-MS using 13C15-DON as an IS has produced comparable results to the 13C-IS-LC-MS-MS reference method with a similar sensitivity. ECD detection was slightly less sensitive, but is also suited for DON analysis in wheat. Due to the high LOQ, the LC-DAD method seems highly applicable to the measurement of highly contaminated samples.
The contamination of infant food with substances from its packaging due to migration processes is still a problem. Most recently, great attention was paid to the migration of epoxidized soybean oil (ESBO) and phthalates from twist-off closures into baby food packed in glass jars. Besides, packaging made of recycled fiber materials such as paper and paperboard were found to be the source of contaminants in dry and powdery foodstuffs such as sugar, rice, and maize flour. In this study 20 infant food samples packed in recycled paperboard containers were tested for phthalates and diisopropyl naphthalenes (DIPN), known incorporated substances in recycled paper. Furthermore, the barrier function of different secondary packaging materials (paper and aluminum-coated foil) was investigated. The highest contents of phthalates (mainly diisobutyl phthalate, DiBP) and DIPN in infant food samples were found for those foods packed in inner bags made of paper. Migration experiments were performed under authentic conditions to evaluate possible transfer mechanism (gas phase, direct contact) of phthalate esters into foodstuff. It is shown that paper does not provide an appropriate barrier against migration of semipolar compounds such as phthalates. The air space itself otherwise effectively prevents migration of the less volatile phthalates under the applied conditions.