Carbon instrumental configuration

Bixler, J.W., Bond, A.M., Lay, P.A. et al. (1986) Instrumental configurations for the determination of sub-micromolar concentrations with carbon, gold and platinum microdisc electrodes in static and flow-through cells. Analytica Chimica Acta, 187, 67. 

Improved sensitivity of NMR instruments has enabled the development of methods for the measurement of carbon-carbon coupling constants, particularly the long-range coupling constants, which are expected to complement the proton-proton and proton-carbon coupling constants in the configurational and conformational analysis of compounds. 

This paper describes the configuration of oxygen and carbon impurities in silicon and techniques which can be used to improve the quality and quantitative accuracy of IR absorption spectra obtained on FT-IR instruments. It also discusses instrument-to-instrument... 

Lycorine (I R, Ri = H) is the most abundant alkaloid in the Amaryl-lidaceae. Classic chemical degradations elucidated the fundamental carbon skeleton and the positions of most functional groups within this nucleus. More subtle problems associated with the position of olefinic unsaturation and the relative and absolute configuration of the alkaloids have been examined by modern chemical and instrumental methods. Simultaneously, fundamental research in NMR-, CD-, ORD, and mass-spectroscopy has been furthered by the ready accessibility of this series of closely related compounds. 

Although the Cotton effects of a-amino acids can be measured directly with up-to-date ORD/CD equipment, more often it is advantageous to form chromophoric derivatives or complexes whose chiroptical properties reflect the absolute configuration of the a-carbon atom. This is especially important when adequate instrumentation is not available or chromophoric substituents other than COOH or NH2 are present. For instance, in the case of aromatic amino acids, more complex chirospectral patterns have to be considered which might prevent the unequivocal assignment of absolute stereochemistry. Also, minor optically active impurities might interfere with spectral data in the 200-250-nm area. 

FT-NMR instruments of 60 and 90 MHz are available from Anasazi Instruments (www.aiinmr. com) in configurations for proton, carbon, fluorine, phosphorus, and silicon studies, with common research capabilities such as 2D (COSY, HETCOR) and DEPT. The proton spectrum and peak assignments for ibuprofen and a good comparison of S/N, resolution, and second-order effects in the 60 MHz spectrum versus a 90 MHz spectrum for ibuprofen can be found in their application note at http //www.aiinmr.com/applications/60-vs-90mhz-sample-2m-ibuprofen. 

The polymer chain is a "fingerprint of the catalyst active centers, go that study of microstructure of the polymer chain handily provides information about the structure of active centers in the catalyst and the effect of different additives on them. The microstructure of polypropylene is most easily studied in the methyl carbon region of NMR spectra.With modem high field NMR instruments even heptad configurations of PP chain can be determined rather easily, Microstructures of polypropylene up to hexads can be examined in the methylene region of the spectra,... 

The glassy carbon (GC) electrodes (3 mm diameter) were purchased from bioanalytical Science. Cyclic voltammetry was performed with a BAS (Bioanalytical System) potentiostat (Model 100). In the voltammetric experiments, a three-electrode configuration was used, including Ag/AgCl reference electrode and a platinum wire counter electrode. The reflectance FTIR spectra of polymers were obtained using Nicolet NEXUS 870 FTIR instrument. The uv-vis spectra using a Agilent 8453 spectrophotometer. 

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