Analytical methods half-fractional

Halcon Process, t-butyl hydroperoxide, 428 Half-fractional factorial design, analytical methods, 624... 

A method of quantitatively determining mole fractions of stereoisomers by IR differential absorbance measurements has been described by Gendreau and Griffiths (1976). Absorbance spectra of the pure isomers at a certain concentration are subtracted from the absorbance spectrum of the mixture at the same concentration. The method is claimed to be accurate even if the analytical bands of the isomers have different absorption coefficients or half-widths. 

SEC can be used as a measure of both the size and the polydispersity of a synthesised polymer, that is, the ability to be able to find the distribution of the sizes of polymer molecules. If standards of a known size are run previously, then a calibration curve can be created to determine the sizes of polymer molecules of interest in the solvent chosen for analysis (often THF). In alternative fashion, techniques such as light scattering and/or viscometry can be used online with SEC to yield absolute molecular weights that do not rely on calibration with standards of known molecular weight. Due to the difference in size of two polymers with identical molecular weights, the absolute determination methods are, in general, more desirable. A typical SEC system can quickly (in about half an hour) give polymer chemists information on the size and polydispersity of the sample. The preparative SEC can be used for polymer fractionation on an analytical scale.. 

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