Tool for in situ measurements

Taillefert M, Luther GV III, Nuzzio DB (2000) The application of electrochemical tools for in-situ measurements in aquatic systems. Electroanalysis 12 401-412... 

More fluorescence features than just the emission intensity can be used to develop luminescent optosensors with enhanced selectivity and longer operational lifetime. The wavelength dependence of the luminescence (emission spectmm) and of the luminophore absorption (excitation spectrum) is a source of specificity. For instance, the excitation-emission matrix has shown to be a powerful tool to analyze complex mixtures of fluorescent species and fiber-optic devices for in-situ measurements (e.g. 

In this article, magnetic resonance imaging (MRI) technique is described as a diagnostic tool for in-situ visualization of water content in the membrane under fuel cell operation.7-30 Demonstrative applications and measurement procedure using MRI techniques are presented with discussion on water transport involved in PEMFCs. 

These experiments demonstrate that tunable diode laser absorption spectroscopy is well suited for in situ measurements of species concentrations in combustion flows, when a line-of-sight technique is appropriate, and for accurate measurements of spectroscopic parameters needed to characterize high-temperature absorption lines. The technique is sensitive, species specific and applicable to a large number of important combustion species including reactive intermediates, and hence it should prove to be a useful tool in future studies of combustion chemistry. The potential of tunable laser absorption spectroscopy in particleladen flows should also be noted (12), in that modulation of the laser wavelength on and off an absorption line allows simple discrimination against continuum extinction by particles. 

We have developed several new measurement techniques ideally suited to such conditions. The first of these techniques is a High Pressure Sampling Mass Spectrometric method for the spatial and temporal analysis of flames containing inorganic additives (6, 7). The second method, known as Transpiration Mass Spectrometry (TMS) (8), allows for the analysis of bulk heterogeneous systems over a wide range of temperature, pressure and controlled gas composition. In addition, the now classical technique of Knudsen Effusion Mass Spectrometry (KMS) has been modified to allow external control of ambient gases in the reaction cell (9). Supplementary to these methods are the application, in our laboratory, of classical and novel optical spectroscopic methods for in situ measurement of temperature, flow and certain simple species concentration profiles (7). In combination, these measurement tools allow for a detailed fundamental examination of the vaporization and transport mechanisms of coal mineral components in a coal conversion or combustion environment. 

S. Chandra and J. Singh, Capacitance-voltage measurement technique as a tool for in situ characterization of electrochemical etching of silicon, J. Electrochem. Soc. 146, 1206, 1999. 

This discussion formulates what we understand about the diamond growth mechanism. The growth mechanism is related to surface processes that are difficult to describe on the atomic scale because of their complexity and the lack of adequate tools for in situ observation and measurements. In this case, modeling of the growth process is required to fill the gap in experimental data. We refer to the diamond growth process as an active surface CVD because of the importance of surface processes. This requires consideration of the following issues ... 

Badry et al. 1993), but no tools are currently equipped with electrodes for in situ measurements of pH. pH electrodes that operate at high temperatures (e.g., 200-300 C) are currently being developed (Bourcier et al. 1987), and research into their use during subsurface drill-stem tests of formation waters may provide the best results in determining this important variable. 

One strong point of Raman spectroscopy for research in catalysis is that the technique is highly suitable for in-situ studies. The spectra of adsorbed species interfere weakly with signals from the gas phase, enabling studies to be performed under reaction conditions. A second advantage is that typical supports such as silica and alumina are weak Raman scatterers, with the consequence that adsorbed species can be measured at wavenumbers as low as 50 cm-1. These benefits render Raman spectroscopy a powerful tool for studying catalytically active phases on a support. 

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