Techniques for examining

Holzworth and Maga (16) developed a technique for examining the trend in visibility and analyzed data for several California airports. Bakersfield s visibility deteriorated over the period 1948-1957, and Sacramento s visibility decreased over the period 1935-1958. Los Angeles had decreasing visibility from 1932 to 1947, with little change over the period 1948-1959. 

X-ray absorption spectroscopy is an important part of the armory of techniques for examining pure and applied problems in surface physics and chemistry. The basic physical principles are well understood, and the experimental methods and data analysis have advanced to sophisticated levels, allowing difficult problems to be solved. For some scientists the inconvenience of having to visit synchrotron radia-... 

F.a.b.-m.s. is a powerful technique for examining mixtures of carbohydrates. Many examples of such analyses are given in Sections V and VI. Unless the components have very different chemical structures, all will give molecular ions. However, the relative abundance of the ions will not necessarily reflect the relative concentrations of the components. Furthermore, if more than one class of carbohydrate is present, different pseudomolecular ions may be produced for each class. An example of such a phenomenon is given in Fig. 4. 

U-series disequilibria have become a powerful technique for examining the melting process beneath mid-ocean ridges. All available evidence points to the disequilibria... 

The terms nondestructive testing and microanalysis refer to techniques for examining the internal structure and analyzing the composition of objects that, because of aesthetic or other considerations, cannot be studied by conventional techniques. 

The two-micropipette current-clamp technique for examining the massed responses of ion channels on Ascaris body muscle... 

IR spectroscopy is a powerful spectroscopic technique for examining the structure and behavior of intermediates involved in organometallic photochemistry. Examples are given of the combination of IR spectroscopy with matrix isolation, with liquid noble gases as solvents, and with flash generation, for probing novel transients and intermediates. 

NMR spectroscopy has become an indispensable tool for synthetic chemists, and an additional and very useful technique for examining tautomeric and conformational equilibria. 

ESR Studies of Surface Species. ESR has been applied widely in heterogeneous catalysis as a technique for examining the nature and concentration of possible catalytic sites when a material is activated either chemically or thermally (64, 65, 66). ESR studies on the Phillips polyethylene catalyst, Cr03/Si02, are a classical example of this application (67). The interpretation of such ESR studies is questionable since the chemical changes during activation are not well understood, and the nature of the surface species may have to be assumed. 

The following discussion will focus on how to apply the previously discussed concepts to the validation of marketed products. To provide a fuller understanding of this procedure, the manufacture of several dosage forms designed for different routes of administration will be examined. For each dosage form, critical process steps and quality control tests will be identified. Useful statistical techniques for examining the assembled data will be illustrated. It is also important to note that not all of the collected information for a product lends itself to this type of analysis. This will become more apparent as we proceed with the evaluation of the five drugs under consideration. 

A most useful technique for examining surface structure is that of replication. One method is to deposit the sample on a freshly cleaved mica surface on to which carbon (and, if desired, a heavy metal) is vacuum-evaporated. The resulting thin film, with the specimen particles still embedded, is floated off the mica on to a water surface. The particles are dissolved out with a suitable solvent and the resulting replica is mounted on a copper grid. 

Refractive index (RI) The measure of the bending of the path of a light ray when passing from a less dense into a more dense medium, e.g. air to water, or vice versa. It is measured by an instrument called a refractometer. May be used as an analytical technique for examining essential oils. 

Figure 10.1 Comparision of various techniques for examination of defects and voids in materials (OM-optical microscopy, TEM- transmission electron microscopy STM-Scanning tunneling microscopy, AFM-atomic force microscopy, Mech-mechanical techniques).

CRM for road dust (BCR-723) containing 81.3 2.5 Jg/kg Pt, 6.1 1.9 ig/ kg Pd, and 12.8 1.3 Jg/kg Rh, was introduced [49, 228]. It is widely used for quality control of results obtained in the analysis of environmental materials (e.g., airborne particulate matters, dusts, soils, and sediments). Comparison of results obtained using different analytical procedures and interlaboratory studies are recommended when there is a lack of suitable CRM (e.g., in examination of clinical samples). The use of standards based on real matrices (e.g., saliva, plasma, ultrafiltrates, and lung fluids) instead of synthetic solutions is recommended in such analyses. Difficulties with the identification and quantification of different metal species in examined samples make the reliability of results of great importance. The use of various instrumental techniques for examination of particular samples can be helpful. The application of chromatography, mass spectrometry, and electrochemistry [199] HPLC ICP MS and HPLC MS/MS [156] ESI MS and MALDI [162] micellar electrokinetic chromatography, NMR, and MS [167] AAS, ESI MS, and CD spectroscopy [179] SEC IC ICP MS and EC ESI MS [180] and NMR and HPLC [229] are examples of such approaches. 

---