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141.
Matthias Koch Wolfram Bremser Robert K?ppen Rita Kr��ger Tatjana Rasenko David Siegel Irene Nehls 《Accreditation and quality assurance》2011,16(8-9):429-437
Mycotoxins are important non-anthropogenic food and feed contaminants, which can be present on almost every agricultural commodity. Effective consumer protection therefore essentially depends on food surveillance by reliable quantitative analysis enabled by appropriate quality control. Certified (matrix) reference materials (CRMs) are versatile tools to support quality assurance. However, in the case of ochratoxin A (OTA), a hepato- and nephrotoxic mycotoxin, which is regulated in various foods, there is a lack of suitable CRMs. This lack has now been overcome by the development of two European Reference Materials (ERM?) for the determination of OTA in roasted coffee (ERM?-BD475) and red wine (ERM?-BD476). This article discusses the material preparation process as well as the results of homogeneity and stability testing. Furthermore, the results of the in-house certification studies carried out at BAM Federal Institute for Materials Research and Testing are presented and discussed. Interlaboratory comparison studies involving selected expert laboratories with documented expertise in the field of mycotoxin analysis were conducted to confirm the certified values determined by BAM. The certified ochratoxin A values and their corresponding expanded uncertainties (k?=?2) were assigned in full compliance with the requirements of ISO Guide 35 and are as follows: (6.0?±?0.6)???g?kg?1 for roasted coffee, ERM?-BD475, and (0.52?±?0.11)???g?L?1 for red wine, ERM?-BD476. 相似文献
142.
Juvancz Zoltan Bodane-Kendrovics Rita Beleznay Peter Erdelyi Istvan Klujber-Mohr Maria 《Chromatographia》2010,71(1):125-128
1,4-Dichlorobenzene is a frequently used lavatory deodorant although it has strong endocrine disrupting and potential carcinogenic effects. A large amount (approximately 15,000 tonnes annually worldwide) of this compound is released into the environment. This paper deals with the determination of 1,4-dichlorobenzene in a variety of environmental matrices. Various extraction and concentration methods such as charcoal absorbtion tubes and headspace sampling were applied. Sensitive and selective ion monitoring GC-MS measurements were used for determination. Significant concentrations of the compound have been identified in lavatory air, waste water, waste water sludge and human breast milk.
相似文献143.
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145.
In this paper we consider experimental situations requiring usage of a row-column design where v treatments are to be applied to experimental units arranged in b
1 rows and b
2 columns where row i has size k
1i
, i=1,..., b
1 and column j has size k
2j
, j=1,..., b
2. Conditions analogous to those given in Kunert (1983, Ann. Statis., 11, 247–257) and Cheng (1978, Ann. Statist., 6, 1262–1272) are given which can often be used to establish the optimality of a given row-column design from the optimality of an associated block design. In addition, sufficient conditions are derived which guarantee the existence of an optimal row-column design which can be constructed by appropriately arranging treatments within blocks of an optimal block design.Visiting from the Indian Statistical Institute. 相似文献
146.
Sara M. Resnizky Rita R. Plá Raquel C. Jasan Sonia E. Hevia Mónica A. Moreno Rodrigo Invenizzi 《Accreditation and quality assurance》2006,10(11):590-593
The implementation of a quality system based on the ISO/IEC 17025:1999 standard is a growing necessity for analytical laboratories to demonstrate their technical competence. In 2001, the Nuclear Analytical Techniques Group of the Argentine Atomic Energy Commission obtained the recognition of the International Atomic Energy Agency in the application of neutron activation analysis and the accreditation by the national accreditation body. The importance of the participation of the group in the Agency's Regional Programme for Latin America, ARCAL XXVI on Quality Assurance in Analytical laboratories is discussed, as well as the activities performed to attain these objectives. Some improvements worth mentioning resulted from the implementation of the quality system and, following the premise of continuous improvement, changes were introduced aiming at the laboratory re-accreditation. 相似文献
147.
U. Wahl J. G. Correia E. Rita E. Alves J. C. Soares B. De Vries V. Matias A. Vantomme 《Hyperfine Interactions》2004,159(1-4):363-372
We present results of recent emission channeling experiments on the lattice location of implanted Fe and rare earths in wurtzite
GaN and ZnO. In both cases the majority of implanted atoms are found on substitutional cation sites. The root mean square
displacements from the ideal substitutional Ga and Zn sites are given and the stability of the Fe and rare earth lattice location
against thermal annealing is discussed. 相似文献
148.
149.
The Schmidt reaction is the acid-catalyzed analogue of the Curtius reaction and is extensively used in organic synthesis. In this work, the mechanism of this reaction has been explored using DFT calculations at the B3LYP/6-311+G(d,p) level. Protonated formyl azide may undergo rearrangement to the product, protonated isocyanic acid, with simultaneous extrusion of molecular nitrogen (concerted mechanism), or undergo rearrangement to the anti conformer, followed by removal of nitrogen to form the nitrenium ion, which then rearranges to the final product, protonated isocyanic acid (step-wise mechanism). Like the Curtius reaction, it is found that the concerted pathway is definitely preferred. The key role of acidification in decreasing the overall energy barrier is more highlighted in case of phenyl substitution, with negligible effect on the lower homologues. For methoxy and amine substituents, there is very little difference in the activation energies of the concerted and step-wise reactions, with the former being still slightly preferred. Unlike the parent compound, the rearrangement of substituted nitrenium ion in some cases involves side reactions like C-H insertion and cyclization. 相似文献
150.