Microanalytical techniques

SIMS is one of the most powerful surface and microanalytical techniques for materials characterization. It is primarily used in the analysis of semiconductors, as well as for metallurgical, and geological materials. The advent of a growing number of standards for SIMS has gready enhanced the quantitative accuracy and reliability of the technique in these areas. Future development is expected in the area of small spot analysis, implementation of post-sputtering ionization to SIMS (see the articles on SALI and SNMS), and newer areas of application, such as ceramics, polymers, and biological and pharmaceutical materials. 

High purity elements and compounds, organic compounds, organo-metallic compounds, high purity compounds for microchemical and microanalytical techniques, pharmaceuticals... 

To further clarify the scope of our discussion, we present a compilation of existing and developing modem microanalytical techniques in Table 4.3. These techniques routinely use small samples in the aforementioned mass range, with some techniques extending their capabilities to significantly smaller sample sizes. 

To discuss the development of CRMs for the emerging use of microanalytical techniques, one has to be concerned chiefly with the degree of homogeneity of the components in the material at the designated sample size. Basic indications for the homogeneity properties of a CRM for microanalytical methods and the assessment of these properties can be derived from the general requirements ... 

Particularly for direct microanalytical techniques using <10 mg of sample for analysis, it is highly desirable to obtain quantitative information on element- and compound-specific homogeneity in the certificates for validation and quality control of measurements. As the mean concentration in a CRM is clearly material-related, the standard deviation of this mean value should represent the element s distribution in this matrix rather than differences in the analytical procedures used. 

Not all reference materials producers currently employ the various techniques that would characterize materials for microanalytical use. Such techniques include measurement of particle size distribution, particle composition, and the determination of component homogeneity with microanalytical techniques. Nevertheless, some... 

The latest innovation is the introduction of ultra-thin silica layers. These layers are only 10 xm thick (compared to 200-250 pm in conventional plates) and are not based on granular adsorbents but consist of monolithic silica. Ultra-thin layer chromatography (UTLC) plates offer a unique combination of short migration distances, fast development times and extremely low solvent consumption. The absence of silica particles allows UTLC silica gel layers to be manufactured without any sort of binders, that are normally needed to stabilise silica particles at the glass support surface. UTLC plates will significantly reduce analysis time, solvent consumption and increase sensitivity in both qualitative and quantitative applications (Table 4.35). Miniaturised planar chromatography will rival other microanalytical techniques. 

Microanalysis is the common name used to refer to a variety of techniques for identifying, characterizing, and evaluating minute amounts of materials. Some microanalytical techniques are scaled-down versions of well-known conventional or physical analytical techniques others are specialized techniques that can be implemented only on extremely small samples. Table 11 lists the minimum size of samples required for microanalysis and the minimum amount of substance detectable by microanalytical techniques (Janssens and Van Grieken 2004). 

We test the permeability of polymer films or sheets to various vapors and gases by mounting the polymer between chambers that contain different concentrations of the migrant molecules. We can determine the permeability from pressure changes, volumetric changes, or by microanalytical techniques that measure the concentration of the migrant molecules in a stream of gas flowing across the low concentration side of the barrier. 

Capillary electrophoresis (CE) was originally developed as a microanalytical technique for analysis and purification of biopolymers. The separation of bio-... 

Microanalytical techniques were first pioneered in the 1960s, and the earliest paper using X-ray microanalysis on plant materials is that of Lauchli and Schwander in 1966 (1). It was soon realized that microanalysis could provide a link between anatomical studies and plant physiology. It allowed scientists who were interested in aspects of plant mineral relations to pursue their interests at a cellular or even subcellular level. Microanalysis, in its various forms, is now a well-established technique, and one that is continuing to develop. 

With some exceptions (2-4), there have been relatively few recent reviews of microanalysis that have considered applications to plant science. In a previous review of this topic (5), I concentrated almost entirely on methods of specimen preparation for electron probe X-ray microanalysis. Here I highlight further developments in this area, and also broaden the scope of the review to include other microanalytical techniques. This chapter introduces the main types of hardware that are now available for microanalysis, reviews the main techniques used to prepare plant material prior to analysis, and provides protocols for the two major techniques. 

Micro structures in heterogeneous catalysts are closely related to the catalytic properties. TEM and related microanalytic techniques are powerful tools in characterising catalysts at atomic level. The obtained structural information is essential to the understanding of correlations between microstructures and catalytic properties. In this lecture note, the general principle of characterization of catalysts by TEM is introduced and the applications on Pt/Si02 model system and on VPO catalysts are intensively described. 

Surface Microanalytical Techniques for the Chemical Characterization of Atmospheric Particulates... 

Linton, R. W., Physico-Chemical Characterization of Environmental Particles Using Surface Microanalytical Techniques , Ph.D. Thesis, University of Illinois, Urbana, Illinois, 1977. 

In recent years, microanalytical techniques, which permit relatively precise isotopic determinations on a variety of samples that are orders of magnitude smaller than those used in conventional techniques, have become increasingly important. Different approaches have been used in this connection, which generally reveal greater isotope heterogeneity than conventional analytical approaches. As a rule of thumb the smaller the scale of measurement, the larger the sample heterogeneity. 

---