Download
A unified scale is recommended for reporting the NMR chemical shifts of all nuclei relative to the 1H resonance of tetramethylsilane (TMS). The unified scale is designed to provide a precise ratio, Ξ, of the resonance frequency of a given nuclide to that of the primary reference, the 1H resonance of TMS in dilute solution (volume fraction, ϕ < 1%) in chloroform. Referencing procedures are discussed, including matters of practical application of the unified scale. Special attention is paid to recommended reference samples, and values of Ξ for secondary references on the unified scale are listed, many of which are the results of new measurements.
Some earlier recommendations relating to the reporting of chemical shifts are endorsed. The chemical shift, δ, is redefined to avoid previous ambiguities but to leave practical usage unchanged. Relations between the unified scale and recently published recommendations for referencing in aqueous solutions (for specific use in biochemical work) are discussed, as well as the special effects of working in the solid state with magic-angle spinning. In all, nine new recommendations relating to chemical shifts are made.
Standardized nuclear spin data are also presented in tabular form for the stable (and some unstable) isotopes of all elements with nonzero quantum numbers. The information given includes quantum numbers, isotopic abundances, magnetic moments, magnetogyric ratios and receptivities, together with quadrupole moments and line-width factors where appropriate.
Pure Appl. Chem., Vol. 73, No. 11, pp. 1795–1818, 2001.
IUPAC Recommendations 2001
© 2001 IUPAC
IUPAC permission is acknowledged
Abstract
This is a new revised and expanded edition of the book “Planning and Optimization of Experiments,” written by researchers and aimed at any professional wishing to conduct and to analyze experiments in the most efficient manner possible.
The qualities that made previous editions a blockbuster – clear and direct language, humorous style and orientation to real-life applications – are still there.
Among the principal inovations of this new edition are dozens of case studies, a more comprehensive comparative presentation of experiments and an entire chapter devoted to methodology of response surfaces, one of the most used techniques for the optimization of products and processes.
Also, if you are interested in the programs (for the DOS operating system) and in the related tutorials, you can get them for free here on this site.
Authors
Benício B. Neto
Ieda S. Sacrminio
Roy E. Bruns
Abstract
The phenomenon known as electrophoresis is defined as the migration of electrically charged species, which occurs when they are dissolved or suspended in an electrolyte, through which an electric current is applied. This separation technique was developed by the chemist Arne Tiselius for the study of proteins in serum and for this work he won the Nobel prize in 1948. This method, called free solution, was quite limited due to instability of the apparatus, and more significantly, the effects of diffusion and heat generated by the electric field, which compromised the resolution (the separation) of the compounds. These effects were minimized with the introduction of a support medium (gel or paper) that helped to contain the movement of the analytes, so that the effect of diffusion was reduced. However this system provided a low level of automation, a long time of analysis with detection performed visually after the separation. Capillary electrophoresis (CE) is a technique that was introduced in 1981 by Jorgenson and Lukacs and has been increasingly accepted as an important analytical method. In its simplest form the CE is an approximation of the original technique, described by Tiselius, but it employs a capillary tube, filled with an electrolyte, as the name suggests.
Keywords
capillary electrophoresis, capillary, detectors, eletroosmotic flow, molecular diffusion
Authors
Sonia Claudia do Nascimento de Queiroz
Isabel Cristina Sales Fontes Jardim
Universidade Estadual de Campinas, Instituto de Química
Translated by
João C. de Andrade
Revised by
Carol H. Collins
