Retention efficiency, meaning

Alumina membranes having a mean pore diameter of 4 and 50 nm reduce the oil and grease concentration in the wastewater containing lubricating oil from 80-120 mgA in the feed to about 2-4 ppm in the p meate. This is equivalent to a retention efficiency of about 96% [Bhave and Fleming, 1988]. The attainable peimeate flux is close to about 90 L/hr-m. The permeate flaxes for the two membranes are shown in Figure 6.14 where they are compared to conesponding clean water fluxes. 

It was found that the benzene, toluene, mesitylene, durene and hexamethylbenzene tricarbonyl chromium could best be separated and quantitatively determined in mixtures by use of temperature programming with the flame ionization detector. Figure 204 illustrates the separation achieved. It can be seen that the resolution is excellent, and that the retention times of the early components are far enough removed from the tail of the solvent peak that measurements from the original base line are possible in each case. Under isothermal conditions (135°C) using flame ionization, the benzene tricarbonyl--chromium and toluene tricarbonylchromium peaks eluted on the tail of the benzene peaks and the retention time of the hexamethylbenzene tricarbonylchromium was 32.6 minutes. This peak was also considerably broader and flatter when eluted isothermally. For this determination therefore, programmed temperature operation is the most efficient means of analysis not only is the resolution improved, but also the total time of analysis is reduced to 15 minutes. 

Berger [340] has examined the use of pSFC in polymer/additive analysis. As many polymer additives are moderately polar and nonvolatile SFC is an appropriate separation technique at temperatures well below those at which additives decompose [300,341,342], SFC is also a method of choice for additives which hydrolyse easily. Consequently, Raynor et al. [343] and others [284,344] consider that SFC (especially in combination with SFE) is the method of choice for analysing polymer additives as a relatively fast and efficient sample preparation method. Characterisation of product mixtures of nonpolar to moderately polar components encompassing a wide range of molecular masses can be accomplished by cSFC-FID. Unknown polymer additives may be identified quite adequately by means of cSFC-FID by comparison with retention times of standards [343], However, identification by this method tends to be time-consuming and requires that all the candidate compounds are on hand. SFC-FID of some low-to-medium polarity additives on reversed-phase packed columns... 

One of the difficulties with any form of chromatography is that a band of solute is dispersed, becoming less concentrated as it travels through the system. The efficiency of the column is a measure of the amount of spreading that occurs. In the chromatogram in Fig. 2.3b, Vr = the retention volume of a solute and wg = the volume occupied by the solute. This is called the peak width, but remember it means a volume, not a length. 

A highly efficient asymmetric induction was also observed in the addition of the lithium salt of (+)-(5)-34 to acetone (313). The addition product 297 (optical purity ca. 80%) was then oxidized to the corresponding sulfone 298, whose absolute configuration was established as R by means of chemical correlations. The formation of sulfone 298 with the absolute configuration R at carbon proves that, unlike methylation, the addition reaction takes place with retention of configuration. It is worthy of note that the optically active... 

Cationic starch in a paper mill furnish can have additional benefits beyond ash retention and strength. Properly added cationic starch can improve formation in a sheet. With an even distribution of fibers, the natural attraction of water for ionized anionic groups can be counteracted by the addition of cationic counter ions in the form of cationic starch. The flocculation effect that occurs produces much improved drainage on the paper machine. The result is increased speed on the machine yielding greater production rates and overall efficiency. To a paper mill, increased production means increased profitability. 

The main task in technical application of asymmetric catalysis is to maximize catalytic efficiency, which can be expressed as the ttn (total turnover number, moles of product produced per moles of catalyst consumed) or biocatalyst consumption (grams of product per gram biocatalyst consumed, referring either to wet cell weight (wcw) or alternatively to cell dry weight (cdw)) [2]. One method of reducing the amount of catalyst consumed is to decouple the residence times of reactants and catalysts by means of retention or recycling of the precious catalyst. This leads to an increased exploitation of the catalyst in the synthesis reaction. 

It is the rate of separation rather than the efficiency of salt retention that is the primary practical issue in the development of reverse osmosis desalination. In addition to a variety of other factors, the rate of reverse osmotic flow depends on the excess pressure across the membrane. Therefore the problem of rapid flow is tied into the technology of developing membranes capable of withstanding high pressures. The osmotic pressure of sea water at 25 °C is about 25 atm. This means that no reverse osmosis will occur until the applied pressure exceeds this value. This corresponds to a water column about 840-ft high at this temperature. 

The retention of a sample by a column and the resultant column efficiency is principally dependent on the rate of diffusion of the analyte through the column. The diffusion rate is dependent upon both the size and porosity of the resin beads and the viscosity of the eluent. The mean free path of an analyte through a column is increased when the resin particle diameter is reduced and also if the stationary phase resin is more porous. The combination of these diffusion mechanisms is the rate determining step in IEC. 

Whatever the method of control may be it seems evident that it is by no means completely efficient for the solid polymer is always a rather small fraction of the total. Price believes, presumably because any optical activity tends to be concentrated in the crystalline phase, that the amorphous and crystalline polymers are products of two different reactions, one in solution and the other heterogeneous (27). While this view is not impossible, it could be argued that solution reaction might be expected to lead to either inversion or retention of configuration and, hence, optically active polymer. Furthermore, some reports suggest rather strongly that the distinction between the two types of polymer is a rather arbitrary one based in part on polymer symmetry and in part on molecular weight. 

---