Separator selection Efficiency

Equation (16-168) shows that the resolution is the result of independent effects of the separation selectivity (ot), column efficiency [Np), and capacity (k ). Generally, peaks are essentially completely resolved when R, = 1.5 (>99.5 percent separation). In practice, values of R, 1, corresponding to 98 percent separation, are often considered adequate. 

Sizing, 451, 453, 455, 459, 462 Sonic flow, 461 Types, illustrations, 411-421 Rupture disk, liquids, 462, 466 Rupture disk/pressure-relief valves combination, 463 Safely relief valve, 400 See Relief valve Safety valve, 400, 434 Safety, vacuum, 343 Scale-up, mixing, 312, 314—316 Design procedure, 316-318 Schedules/summaries Equipment, 30, 31 Lines, 23, 24 Screen particle size, 225 Scrubber, spray, 269, 270 Impingement, 269, 272 Separator applications, liquid particles, 235 Liquid particles, 235 Separator selection, 224, 225 Comparison chart, 230 Efficiency, 231... 

Prus and Kowalska [75] dealt with the optimization of separation quality in adsorption TLC with binary mobile phases of alcohol and hydrocarbons. They used the window diagrams to show the relationships between separation selectivity a and the mobile phase eomposition (volume fraction Xj of 2-propanol) that were caleulated on the basis of equations derived using Soezewiriski and Kowalska approaehes for three solute pairs. At the same time, they eompared the efficiency of the three different approaehes for the optimization of separation selectivity in reversed-phase TLC systems, using RP-2 stationary phase and methanol and water as the binary mobile phase. The window diagrams were performed presenting plots of a vs. volume fraetion Xj derived from the retention models of Snyder, Schoen-makers, and Kowalska [76]. 

If we consider only a few of the general requirements for the ideal polymer/additive analysis techniques (e.g. no matrix interferences, quantitative), then it is obvious that the choice is much restricted. Elements of the ideal method might include LD and MS, with reference to CRMs. Laser desorption and REMPI-MS are moving closest to direct selective sampling tandem mass spectrometry is supreme in identification. Direct-probe MS may yield accurate masses and concentrations of the components contained in the polymeric material. Selective sample preparation, efficient separation, selective detection, mass spectrometry and chemometric deconvolution techniques are complementary rather than competitive techniques. For elemental analysis, LA-ICP-ToFMS scores high. 

There are four principal factors that are paramount in selecting the best separation technique. They are the energy required for the separation, the capital required for the equipment used in the separation, the efficiency/effectiveness of the separation, and the vitality of the catalyst after the separation. General process considerations include ... 

FIGURE 3.13 Dependence on the resolution of two adjacent peaks from the separation selectivity, column efficiency, and capacity factors of peaks. Curves were calculated by keeping values of two parameters constant at the starting value and varying the third parameter. 

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. 

Capillary electrophoresis offers a set of important advantages that make it a premier technique for the investigation of enantioselective effects in the affinity interactions between chiral drugs and cyclodextrins. The most important advantage of CE is the inherently high separation efficiency offered by this technique. As already known, the most important contributors to peak resolution (R) are a separation selectivity (a) and an efficiency (N). A relationship between these parameters in CE is described by the following equation (2) ... 

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... 

Basically, capillary electrochromatography (CEC) is a hybrid technique of HPLC and CE [1-3], which was developed in 1974 by Pretorius et al. [4]. CEC is expected to combine high peak efficiency, which is a characteristic of electrically driven separations, with high separation selectivity. As is the case for electrophoresis, a voltage is applied across the separation plateform and sample moves via electroosmotic flow (EOF). However, in analogy to liquid chromatography, the separation device contains a solid... 

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 success of a particular analytical or preparative HPLC strategy with polypeptides or proteins is predicated by the ease of resolving to a predefined level the desired component from other substances, many of which may exhibit similar separation selectivities but are usually present at different abundance levels. For high-resolution purification procedures to be carried out efficiently, it is self-evident that rapid, multistage, high-recovery methods must be utilized. To minimize losses and improve productivity, on-line, real-time evaluation of each of the recovery stages is an essential objective. Furthermore, overall optimization and automation of the individual unit operations must be achieved. Similar criteria but with different endpoints apply in high-resolution analytical application. 

Preparative liquid chromatography (in opposition to analytical chromatography) introduces specific requirements, which are mostly related to the separation selectivity and the loadability of a solid phase rather than the separation efficiency or peak resolution. While analytical chromatography separations may use complex profiles of elution gradients, in most of the cases, preparative chromatography utilizes linear or step gradients or a combination of both. 

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

We have found that the use of 3% n-propanol in the micellar mobile phase and column temperatures of 40° C appear to offer a broadly applicable solution to the low efficiency previously reported for micellar mobile phases. These conditions have resulted in reduced plate heights of 3-4 for SDS, cetyltrimethylammonium bromide (CTAB), and Brij-35 (15). This efficiency optimization scheme then appears to be a broadly-based solution for micellar mobile phases of any surfactant. This means that the surfactant type can be varied to affect separational selectivity with no loss in column efficiency. 

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

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. 

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