Analytical Intercomparison Exercises and Harmonization within Environmental Laboratories from Developing Countries

Abstract

Since the early 60's, the IAEA implements a Quality Assurance (QA) programme for the Member States. As part of this programme, the IAEA organized more than 150 analytical intercomparison exercises and produced more than 70 Certified Reference Materials for a wide range of determinands, encompassing radionuclides, trace elements, petroleum hydrocarbons, pesticides and PCBs. From the IAEA — Marine Environment Laboratory in Monaco, analytical Quality Assurance services are provided for non-nuclear contaminants in marine materials.

Results of recently organized worldwide intercomparison exercises using the sample materials IAEA-142 (mussel tissue homogenate) and IAEA-140 (seaweed homogenate), show that some progress was achieved worldwide in the analyses of the more common environmental contaminants. However, results also show that difficulties in obtaining accurate data for trace elements and especially for organic contaminants are still widespread, particularly in developing countries. Therefore, the success of international cooperative programmes as well as of many regional environmental monitoring programmes, depends on improved quality and comparability of data which has to be achieved still through reinforced Quality Assurance programmes. To this aim, the IAEA/UNEP/IOC-UNESCO inter-agency programme on marine pollution promotes the adoption of Reference Methods for harmonization of techniques used in developing and developed countries, organizes frequent intercomparison exercises, and produces certified marine Reference Materials which are made available to laboratories worldwide.     

High harmonic generation and molecular orbital tomography in multielectron systems: beyond the single active electron approximation

It was recently shown that the highest molecular orbital of N2 could be reconstructed from a series of high harmonic measurements. Existing theories of high harmonic generation and orbital tomographic imaging are based on the single active electron approximation that ignores essential quantum mechanical properties such as the indistinguishability of identical particles and the Pauli exclusion principle. We show that, when fully antisymmetrized multielectron wave functions and electronic relaxation in the cation are considered, molecular orbital tomography records the image of the Dyson orbital plus exchange contributions from inner shells. The mixing of contributions from more than one molecular orbital gives access to additional wave function information. By utilizing the exchange term, harmonic emission from a closed-shell 4-electron system can be interpreted as a complete Hartree-Fock wave function.     

Study on the reactivity of the alkyne component in ruthenium-catalyzed [2 + 2] cycloadditions between an alkene and an alkyne

The ruthenium-catalyzed [2 + 2] cycloadditions of norbornadiene with a variety of alkynes have been investigated. Electronic effect of the alkyne component has shown to play an important role on the rate of the cycloaddition, and the reactivity of the alkyne component increases dramatically as the alkyne becomes more electron deficient. Increase in the steric bulk of the alkyne component decreases the reactivity of the alkyne component. It was also found that chelation effect of propargylic alcohols greatly enhanced the reactivity of the alkyne component in the ruthenium-catalyzed [2 + 2] cycloadditions.