Chemical sensitivity abbreviations

The dye NKX-2311, shown in Fig. 1, was kindly given by Hayashibara Biochemical Laboratories. The physical and chemical properties of the dye have already been reported [9], The ZnO and Ti02 films were prepared on a glass or sapphire substrate by a similar procedure reported elsewhere [10], The dye was loaded by just immersing the bare ZnO and T1O2 films into dye solution to make dye-sensitized films, abbreviated as NKX-2311/ZnO and NKX-2311/Ti02, respectively. 

Magnetic and electrical interactions of the nucleus with its environment (e.g., other magnetic nuclei or electrons) produce small shifts in the NMR frequency away from Vo obs = Vo + Av. These interactions, measured by their frequency shifts, convey structural and chemical information. The most useful of these interactions is the so-called chemical shift , which results from magnetic shielding of the nucleus by nearby electrons, which circulate due to the presence of Bq. The chemical shift (5) is very sensitive to the electronic structure, and hence the local structural and chemical environ-ment of the atom. The chemical shift is measured by the frequency difference from a convenient reference material, rather than from vo directly 5=10 (Vsampie - Vref)/Vref- For example, tetramethylsilane (Si(CH3)4, abbreviated IMS) serves as the standard frequency reference... 

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The standard substance almost universally used is tetramethylsilane (Me4Si), commonly abbreviated as TMS. This standard was chosen because it gives rise to a single sharp line as a result of the identical environment of all the protons in the symmetrical molecule and because the chemical environment of protons in TMS is such that they resonate at a higher field than practically any other proton. Further, TMS is an inert, low-boiling liquid and can be easily removed from the sample after the spectrum has been run. Therefore, in practice, the procedure is nondestructive. The sample size required for examination by NMR, however, is relatively large, generally at least 10 mg, because of the inherently low sensitivity of the method. 

Assuming no conformation dependent chemical shift effects to occur and using the chemical shift of orthorhombic polyethylene (33 ppm) [6] we can now calculate the chemical shifts of the methine carbon atoms in the three triads of the solid crystalline E-VOH copolymer, respectively 000 (67 ppm), CX)E (70.4 ppm) and EOE (73.8 ppm) where 000, OOE, EOE are abbreviations for (VOH, VOH, VOH), (VOH, VOH, E) and (E, VOH, E) triads. The chemical shift values presented above are only meant to yield useful assignments of the several methine carbon NMR signals of E-VOH copolymers. These assignments are necessary because Ovenall [5] did not report dependable estimates for all three types of methines sustained by experimental results. We are aware of chemical shift differences between liquids and solids. Moreover, the choice of orthorhombic polyethylene as a basis for the shift calculations is rather arbitrary but this will only cause the same uncertainty in each of the three shifts. Of more importance is the known sensitivity of substituent-induced shifts towards different conformational equilibria. From results obtained by Cantow [7] for different poly (1,2-dimethylbutane) polymers it can be estimated that the uncertainties in our estimations amount to ca. 2 ppm. It is, however, improbable that the order of the three methine carbon signals will be misjudged. 

Consequently, this review is designed to briefly summarize many of the available techniques for accurate measurements of environmental and human lead contamination. This includes the importance of ultraclean techniques for lead analysis as well as brief descriptions of some current and emerging analytical techniques for measuring lead exposures in humans. The descriptions are preceded by abbreviated discussions of the chemical properties of lead, natural and anthropogenic variations in its stable isotopic composition, and historical records of lead contamination in the environment. The report concludes with a summary of some indirect methods of measuring lead exposure and toxicity in humans. Much of the material in this report is based on reviews written for several recent reports Measuring Lead Exposure in Infants, Children, and Other Sensitive Populations (NRC 1993), Lead in the Biosphere Recent Trends (Smith and Flegal 1995), and In Vivo Measurement and Speciation of Nephrotoxic Metals (Smith and McNeill 1995). 

X-ray photoelectron spectroscopy (XPS, commonly termed ESCA as an abbreviation for electron spectroscopy for chemical analysis) is eminently suited to the study of surfactant adsorption. The XPS method is highly sensitive to the surface composition and can characterize adsorbed surfactant layers without elaborate sample preparation. 

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