Fractional polarization Free volume

DMABN suffers from the fact that dual fluorescence is only observable for polar media. Therefore, the pretwisted ester DMPYRBEE has been developed which shows dual fluorescence also in alkane solvents. 9 This probe allowed measurement of nonpolar polymeric siloxane oils and a comparison with the corresponding measurements using an EXCIMER probe. As expected from the decreased reaction volume necessary for the TICT photoreaction, the latter is usable down to much lower temperatures (higher viscosities) and probes a larger fraction of free volume. 26 ... 

We define a nucleation overpotential rjN EN E0 (Fig. 36) required to make the N0 oxidation nuclei appear. The nucleation overpotential is related to the degree of closure (compaction) of the polymeric entanglement ( ), expressed as the fraction of interchain free volume destroyed after polarization at a given potential Ec, compared with the amount of free volume present at Es. 

Some results for the effects of addition of different lipid compounds on loaf volume of a base flour are shown in Figure 7.10 (Sroan 2007). The natural lipid from flour has been separated into two fractions polar and nonpolar. Thin layer chromatography (TLC) of the fractions is shown in Figure 7.11. Polar lipids comprise mainly galactolipids and phospholipids. Their addition enhances loaf volume. In contrast, the nonpolar fraction, which comprises mono-, di-, and triglycerides and free fatty acids as the main components, causes depression of the loaf volume. The unsaturated linoleic acid, which is the major fatty acid in wheat, also depresses loaf volume, whereas the saturated palmitic acid has no effect. Another saturated fatty acid, myristic acid, affected loaf volume negatively. 

Extraction of nonpolar compounds using equal volumes of sample and the Folsch mixture (2 1, chloroform/MeOH) gives a very broad polarity cut. Everything from steroids to triglycerides is pulled down into the bottom chloroform-rich layer. Extraction with methylene chloride from a sample acidified with sulfuric acid is more specific, pulling in steroids, fat-soluble vitamins, and free fatty acids. The triglyceride fraction can be extracted using i-PrOH/ hexane (1 9) with little emulsification. 

The methanol at room temperature extracts both fats and volatiles. Cooling the methanolic extract desolublized most of the fat retaining most of the volatiles in solution. The alcoholic solution was then diluted with nine volumes of water. Back extraction of the aqueous solution with Freon 113 followed by ethyl acetate yielded a non-polar and a polar fraction free of many contaminating non-volatiles. In this procedure acetonitrile, but not isopropyl alcohol, was a good replacement for methanol and pentane is a good replacement for Freon 113. The idea is similar to the estab-... 

Doubling the volume fraction of one phase doubles the probability of solute interaction and, consequently, doubles its contribution to retention. There is another interesting outcome from the results of Purnell and his co-workers. Where a linear relationship existed between the retention volume and the volume fraction of the stationary phase, the linear functions of the distribution coefficients could be summed directly, but their logarithms could not. In many classical thermodynamic descriptions of the effect of the stationary-phase composition on solute retention, the stationary-phase composition is often taken into account by including an extra term in the expression for the standard free energy of distribution. The results of Purnell indicate that this is not acceptable, as the solute retention or distribution coefficient is linearly not exponentially related to the stationary-phase composition. The stationary phases of intermediate polarities can easily be constructed from... 

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