Dynamic reaction cell technology

The complexity of analyte matrixes and the low level of selenium compoimds even in em-iched samples make speciation difficult, but the combination of separation processes with selenium-specific detection is a powerful approach. High sensitivity is vital, and MS with an atmospheric pressure ionization source, such as the ICP, has proved successful for HPLC detection. Selenium presents problems due to moderate ionization efficiency and isobaric interferences, although these can be partly overcome with high-resolution mass spectrometers or dynamic reaction cell (DRC) technology. Significant isotopic overlap from " °Ar2 on the most abundant isotope Se (49.6%) may necessitate measurement of the less abundant isotopes Se (8.6%) or Se (7.6%) of total selenium. 

The first commercial instrument to use this approach was called dynamic reaction cell (DRC) technology Similar in appearance to the hexapole and octapole collision/reaction cells, the DRC is a pressurized multipole positioned prior to the analyzer quadrupole. However, this is where the similarity ends. In DRC technology, a quadrupole is used instead of a hexapole or octapole. A highly reactive gas such as ammonia, oxygen, or methane is bled into the cell, which is a catalyst for ion-molecule chemistry to take place. By a number of different reaction mechanisms, the gaseous molecules react with the interfering ions to convert than into either an innocuous species different from the analyte mass or a harmless neutral species. The analyte mass then emerges from the DRC free of its interference and is steered into the analyza quadrupole for conventional mass separation. 

Kawabata, K., Kishi, Y., and Thomas, R. (2003) The benefits of dynamic reaction cell ICP-MS technology to determine ultra trace metal contamination levels in high-purity phosphoric and sulfuric acid. At. Spectrosc., 24, 57-65. 

For these reasons, ICP-MS has proved to be a very attractive option for the analysis of foodstuffs, especially since modern instruments fitted with collision/reaction cell or interface technology have the capability to extend the dynamic range to determine higher levels, as well as the ability to determine low levels of the traditionally... 

In spite of well-developed classical theory, the interest to investigation of synchronization phenomena essentially increased within last two decades and this discipline still remains a field of active research, due to several reasons. First, a discovery and analysis of chaotic dynamics in low-dimensional deterministic systems posed a problem of extension of the theory to cover the case of chaotic oscillators as well. Second, a rapid development of computer technologies made a numerical analysis of complex systems, which still cannot be treated analytically, possible. Finally, a further development of synchronization theory is stimulated by new fields of application in physics (e.g., systems of coupled lasers and Josephson junctions), chemistry (oscillatory reactions), and in biology, where synchronization phenomena play an important role on all levels of organization, from cells to physiological subsystems and even organisms. 

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