Microscopic specie analysis

For chemical speciation, X-ray absorption spectroscopy is another supreme tool taking advantage of its electronic and structural information power. Also, REMPI-MS is outstanding in its selectivity for molecular species. Radioanalytical methods have also been used for speciation analysis [548]. Microscopical speciation analysis requires SSIMS or LMMS [549]. 

Network properties and microscopic structures of various epoxy resins cross-linked by phenolic novolacs were investigated by Suzuki et al.97 Positron annihilation spectroscopy (PAS) was utilized to characterize intermolecular spacing of networks and the results were compared to bulk polymer properties. The lifetimes (t3) and intensities (/3) of the active species (positronium ions) correspond to volume and number of holes which constitute the free volume in the network. Networks cured with flexible epoxies had more holes throughout the temperature range, and the space increased with temperature increases. Glass transition temperatures and thermal expansion coefficients (a) were calculated from plots of t3 versus temperature. The Tgs and thermal expansion coefficients obtained from PAS were lower titan those obtained from thermomechanical analysis. These differences were attributed to micro-Brownian motions determined by PAS versus macroscopic polymer properties determined by thermomechanical analysis. 

Probably the most extensive use of particle morphology and microscopy has been in the area of chemical microscopy. With this approach, derivatives of the analyte species are prepared, crystallized, and identified through the morphological characteristics of these derivatives [21]. Most of these applications have been superseded by modem methods of analysis, but the microscopic method can still be used by skilled practitioners for the study of trace quantities of analyte. The literature developed during the heyday of chemical microscopy is too large to be reviewed here, but advances in the field are still chronicled in the Annual Reviews issue of Analytical Chemistry [22]. A substantial review of the optical characteristics of organic compounds is available [23]. 

After the experiment, the experimental charge is prepared for analysis of the diffusion component or species. The analytical methods include microbeam methods such as electron microprobe, ion microprobe, Rutherford backscatter-ing, and infrared microscope to measure the concentration profile, as well as bulk methods (such as mass spectrometry, infrared spectrometry, or weighing) to determine the total gain or loss of the diffusion component or species. Often, the analysis of the diffusion profile is the most difficult step in obtaining diffusivity. 

In this manner the unpaired election spins may be used as a probe foi analysis of their immediate microscopic surroundings. Typical instrument sensitivity is such that approximately ]0-11 mole of a paramagnetic species can be detected, but generally concentrations of 10 4 mole give optimum ESR spectra. 

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