Selective efficiency

Actually, because the alternate scheme is based on 75% efficiency, if the values are corrected for the differences in efficiency of the two individual compressor cases used, the results will be close enough for engineering application. As they stand, the bhp values cannot be resolved to a more accurate basis without specific data on case selection, efficiency, and losses. 

Catalytic kinetic resolution can be the method of choice for the preparation of enantioenriched materials, particularly when the racemate is inexpensive and readily available and direct asymmetric routes to the optically active compounds are lacking. However, several other criteria-induding catalyst selectivity, efficiency, and cost, stoichiometric reagent cost, waste generation, volumetric throughput, ease of product isolation, scalability, and the existence of viable alternatives from the chiral pool (or classical resolution)-must be taken into consideration as well... 

The resolution of two peaks is related to the adjustable chromatographic variables of selectivity, efficiency, and time by equation (1.46) (104-106)... 

Fundamental concepts of retention, selectivity, efficiency, and peak resolution... 

This chapter provides an overview of essential concepts in HPLC including retention, selectivity, efficiency, and resolution as well as their relationships with key column and mobile phase parameters such as particle size, column length and diameter, mobile phase strength, pH, and flow rate. The significance of several concepts important in pharmaceutical analysis such as peak capacity, gradient time, void volume, and limit of quantitation are discussed. 

The fact that the EP wants to replace old TEC methods with more selective, efficient, and sensitive separation methods provides the chance for the introduction of more CE methods. The continuous development of analytical methods is reflected in the national and international pharmacopoeias. This might be demonstrated for atropine sulfate. Whereas the Deutsches Arzneibuch, 7th Edition (DAB 7) only limits the tropic acid by extraction and titration with NaOH and phenolphthalein indication, the 4th edition of the EP looked for foreign alkaloids and decomposition products by means of TEC with a potassium iodobismuthate for detection. By intensity comparison of the obtained spots, it was possible to limit these impurities to 0.5%. The EP 5 utilizes an ion-pair HPLC method that is able to limit most of the impurities to less than 0.2%. To make the method more robust, an HPLC method using a polar embedded was applied, which might be the next step for the EP. However, recently the same authors have reported on a MEEKC method being as robust and precise as the latter HPLC method (see Eigure 6) but far more sensitive and, therefore, a future perspective for the EP. 

It strikes me that in biological membranes, at least in eucaryotic cells, the transport mode almost universally chosen is the channel, or pore, mode, and not the mobile carrier mode. Surely there must be reasons for this, and it would seem appropriate to me if either Professor Simon or Professor Eisenman could start this discussion with a description of the respective merits of the two transport modes, with respect to selectivity, efficiency, and other parameters. 

Resolution is a measure of the relative separation achieved between two chromatographi-cally distinct materials, and maximum resolution is the primary goal of any purification step. This discussion covers the main theoretical parameters that affect ability to resolve components of a protein sample into chromatograph i-cally distinct forms, thereby providing a basis on which to judge chromatographic results. The main parameters affecting resolution are selectivity, efficiency, and capacity. More detailed... 

The selection efficiency is evaluated by the ratio of the output over input titers. After each selection, the phages are amplified and can be subjected to anew selection round. If some clones of the library are effectively selected, the ratio should increase from around 10-5 (background level) to around 10-2. Typically, the ratio reaches a plateau after about 4 to 8 selection rounds - depending on the starting diversity and on the power of the selection itself. 

Markovitz HM (1959) Portfolio Selection Efficient diversification of investments. John Wiley Sons, New York et al. 

Certainly, the selectivities, efficiencies, reproducibilities, and applications of nanoliquid chromatography (NLC) and nanocapillary electrophoresis (NCE) machines depend on the materials used for microchips. The microfabrication technologies originated from the microelectronics industry using silicon... 

Preparative-scale chromatography relies on a compromise between three variables (cf. Figure 1) (i) component resolution (determined by selectivity, efficiency and retention factor), (ii) speed of analysis and (iii) column sample capacity (Pescar, 1971). Any two of the desired goals may be realized only at the expense of the third. If a large amount of sample is required in a short time, resolution must be high. If resolution is insufficient, either the column load is limited or the time required for separation is long. 

The selection efficiency is also dependent on the percentage of phage(mid) particles which display a particular antibody. This usually varies between 1 % and 10%, although it can be far lower [14]. The selection of two antibodies with similar affinities but different display levels will result in the preferential recovery of the antibody with the highest display level. The level of display is the result of a number of different parameters, including (1) antibody folding within the periplasm, (2) resistance to proteolysis, (3) resistance to aggregation, and (4) toxicity to the bacterial expression host. 

Wide scope vs. high sensitivity Time constant The separation Capacity factor Selectivity Efficiency Resolution... 

It has been recently reported that the reactions of 1,4-dilithio-l,3 dienes with carbon monoxide provides a useful tandem methodology for the synthesis of cyclopentenones14. The reaction constitutes an unprecedented pattern of highly selective efficient carbonylation, since in 1 h at — 78 °C it affords, after hydrolysis, fraws-3-cyclopenten-l-one in an excellent isolated yield and with perfect trans selectivity. 

Advantages - Mild reaction conditions - High activity selectivity - Efficient heat transfer - Facile separation of catalyst and products - Continuous processing... 

The effect of the nature of a chaotropic mobile phase additive on retention behavior of basic drugs analytes was studied. They influence the selectivity, efficiency, and repeatability [87,95,108]. Interestingly, weakly chaotropic ions such as those coming from acetic [94,109-111] or phosphoric add were advantageously used as IPRs [16,89-91] and the results may be rationalized by the theory of chaotropicity [95]. 

Improvements in the selectivity of the separation of microcystins and nodnlarin have been achieved by selecting the most efficient stationary phase, with this aim (Spoof 2002) compared a monolithic C-bonded silica rod colnmn (Merck Chromolith) to particle-based C and antide C 18 18 16 sorbents in the HPLC separation of eight microcystins and nodularin-R. Two gradient mobile phases of aqneons trillnoroacetic acid modified with acetonitrile or methanol, different flow-rates, and different gradient lengths were tested. The performance of the Chromolith colunrn measured the resolution of some microcystin pairs. The selectivity, efficiency (peak width), and peak asymmetry equalled, or exceeded, the performance of traditional particle-based columns. The Chromolith 21 colnmn allowed a shorteiting of the total analysis time to 4.3 minutes with a flow rate of 4 ml/minute. 

Evaluation parameters are retention time, selectivity, efficiency or plate number, HETP values and resolution. They characterize the performance of a certain chromatographic separation and are indicators for the selection (or better definition) of a chromatographic system. Strictly speaking they are defined for linear chromatography only. 

Resolution can be increased if one of the three terms in Eq. 4.14 is increased. As mentioned in Chapter 2.4.3 the first term describes the influence of selectivity. This term should be maximized by maximizing a in a selectivity screening with different adsorbents and mobile phases. The second term should be kept in a certain range and not be maximized, because the maximum value of 1 is reached for an infinite retention factor. At infinite retention the productivity would decrease due to the high cycle time. The last term of Eq. 4.14 describes the efficiency of the column in terms of the number of plates. Resolution can be increased by selecting efficient adsorbents with small particle size and appropriate narrow particle size distribution. For these adsorbents fluid dynamic and mass transfer resistances are minimized. Con-... 

The most important goal of chemistry is to create new materials. Up to now, more than 30 million compounds have been created by scientists. However, the methods for their synthesis and preparation are still mainly based on a trial-and-error approach. With the development of science and the progress of social civilization, developing atom-economic and highly selective, efficient, and versatile synthetic methods to create new materials based on functional requirements have become key issues for the development of chemistry in the new century. 

---