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Made D.,State Office for Consumer Protection Saxony Anhalt | Trubner K.,State Office for Consumer Protection Saxony Anhalt | Neubert E.,Saxon State Laboratory of Health and Veterinary Affairs | Hohne M.,Robert Koch Institute | Johne R.,German Federal Institute for Risk Assessment
Food and Environmental Virology | Year: 2013

During September/October 2012, a norovirus gastroenteritis outbreak affecting about 11,000 people occurred in Germany. Epidemiological studies suggested that frozen strawberries represented the vehicle of infection. We describe here the analysis of frozen strawberries for the presence of norovirus. Samples were taken by applying a stratified subsampling scheme. Two different methods for virus extraction from strawberries were compared. First, viruses were eluted from strawberries under alkaline conditions and concentrated using a polyethylene glycol precipitation. Second, ultrafiltration was applied for concentration of viruses rinsed off of the berries. In both cases, RNA was extracted and analyzed by real-time RT-PCR. Application of the ultrafiltration method generally resulted in a lower detection rate. Noroviruses were detected in 7/11 samples derived from the lot of strawberries implicated in the outbreak using the precipitation method. Typing of norovirus revealed three different genotypes including a combination of norovirus genotype II.16 (viral polymerase) and II.13 (viral capsid). This genotype combination was also found in some of the patients that were involved in the outbreak, but that had not been reported in Germany so far. In conclusion, heterogeneously distributed noroviruses in frozen strawberries can be detected by applying an optimized combination of sampling procedures, virus extraction methods, and real-time RT-PCR protocols. The detection of several different genotypes in the strawberries may suggest contamination from sewage rather than from a single infected food handler. © 2013 The Author(s).


Hildmann F.,Saxon State Laboratory of Health and Veterinary Affairs | Hildmann F.,TU Dresden | Kempe G.,Saxon State Laboratory of Health and Veterinary Affairs | Speer K.,TU Dresden
Journal of Separation Science | Year: 2013

Precolumn back-flushing is a matrix minimization technique in GC in which the carrier gas flow of the precolumn is reversed after the transfer of the highest boiling analyte to the analytical column. Practical details concerning this technology have rarely been published although it is widely used. This paper now focuses on the practical implementation of precolumn back-flushing for pesticide residue analysis of complex food matrices. Fitting the analytical column into the precolumn was found to be essential for comparable analyte responses with and without back-flushing. The effectiveness of the reverse column flow technique is mainly affected by the transfer time after which back-flushing starts. The transfer time was found to depend on which kind of injected matrix is used and the state of the precolumn. For the regular adaptation of the transfer time in routine analysis, a simple test was introduced in which 13-C-labeled deltamethrin and indeno[1,2,3-c,d]pyrene were added to the prepared extract. Chromatograms, LOQ and RSD of up to 99 pesticides in citrus oil and liver extracts proved a clearer identification and enhanced quantification using precolumn back-flushing compared to measurements without this technology. Furthermore, reduced system maintenance could be achieved through back-flushing. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Hildmann F.,Saxon State Laboratory of Health and Veterinary Affairs | Hildmann F.,TU Dresden | Gottert C.,Saxon State Laboratory of Health and Veterinary Affairs | Frenzel T.,Saxon State Laboratory of Health and Veterinary Affairs | And 2 more authors.
Journal of Chromatography A | Year: 2015

A sample preparation method was developed for the analysis of chicken eggs to determine 97 GC and 81 LC amenable residues, including organophosphates, organochlorines, pyrethroids, triazoles, carboxyl-containing compounds, and the indicator PCBs. Hereby, considerations were given to the recoveries of the analytes, the method's suitability for routine analysis, and the assessment of the clean-up effect, for which a simple thin layer chromatography was implemented to visualize the most important lipid classes.The procedure consisted of (I) the extraction by matrix solid phase dispersion, and the clean-up by means of (II) small-scale gel permeation chromatography (GPC) and (III) two different solid phase extractions (SPE) for GC and LC amenable analytes, as well as (IV) the quantification using GC-MS/MS and LC-MS/MS. Cyclohexane/ethyl acetate was chosen as extraction solvent due to its suitability for extracting strong non-polar but also more polar analytes. The classical GPC was scaled down to ensure a 50% lower solvent consumption. The comprehensive investigation of conventional and modern zirconium-oxide-coated SPE materials resulted in the selection of octadecyl-modified silica (C18) combined with primary secondary amine using acetonitrile as elution solvent for GC amenable analytes and pure C18 in combination with acidified methanol for LC amenable pesticides.Compared to the currently established EN 1528 method the sample preparation proposed offered a higher sample throughput and a lower solvent consumption. Furthermore, for the first time the clean-up effectiveness of the sample preparation steps was documented as shown by means of thin-layer chromatography.The validation of chicken eggs proved the fulfillment of the quality control criteria for 164 of the 178 analytes tested, mostly at the lowest validated level of 5. μg/kg for pesticides and 0.5. μg/kg for the single indicator PCBs. However, the analysis of strongly polar analytes was still problematic, which could be attributed to the extraction and the GPC step. Nevertheless, the successful investigation of EU proficiency test materials (EUPT AO 07-09) confirmed the comparability of the results with the currently established sample preparation procedures and demonstrated the potential of the applicability of the presented method to other matrices as exemplified for lean poultry meat and fatty liquid cream. © 2015 Elsevier B.V.

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