Separation techniques, classification

Because membranes appHcable to diverse separation problems are often made by the same general techniques, classification by end use appHcation or preparation method is difficult. The first part of this section is, therefore, organized by membrane stmcture preparation methods are described for symmetrical membranes, asymmetric membranes, ceramic and metal membranes, and Hquid membranes. The production of hollow-fine fiber membranes and membrane modules is then covered. Symmetrical membranes have a uniform stmcture throughout such membranes can be either dense films or microporous. 

TABLE 5.1 Classification and Examples of Two-Dimensional Liquid-Phase Separation Techniques... 

The classification of separation techniques as shown in Table 3.2 is concise and easy to remember but it is also simplistic because it appears to imply that only one factor is involved in each technique. In practice, the effectiveness of any method is a composite of many factors, the one indicated in the table usually being the most significant. Some of the developments in separation procedures exploit this range of factors involved in any separation technique by using conditions or reagents designed to minimize one or maximize another. As a consequence, the techniques and instrumentation of separation methods are constantly changing but the fundamental principles remain the same and need to be understood in order to appreciate the usefulness and limitations of any particular technique. 

Figure 5.2 — Classification of (bio)chemical flow-through sensors based on integrated reaction, separation and detection according to the type of separation technique involved.

Once explored the sensor data by PCA and determined that the four types of honey could be separated, a classification model was performed by the ANN technique. The results of ANN analysis can be visualised... 

Table 4.1 Classification of separation techniques TKCHNiyUI PHASE SYSTEM ...

In complex systems where the number of groups to be separated during classification becomes larger, the performance of simple unsupervised methods (Section 3) degrades, requiring the use of more sophisticated supervised chemometric techniques. Additionally, in fields such a process NMR where there is a need for quantifying a component, the use of supervised methods becomes necessary. The different supervised methods described in the sections below have all been utilized in the chemometric analysis of NMR data for classification and/or quantitation. Examples utilizing these different techniques are discussed in Section 5. 

TABLE 17,1-1 Classification and Principles of Major Separation Techniques... 

These are arbitrary classifications of chromatographic techniques, and some types of chromatography are considered together as a separate technique, such as gas chromatography for gas-solid and gas-liquid chromatography. In every case, successive equilibria are at work that determine to what extent the analyte stays behind or moves along with the eluent (mobile phase). In column chromatography, the column may be packed with small particles that act as the stationary phase... 

Many similarities in equipment and methodology exist between HPLC and FI separation methods, particularly those involving column separation techniques, and occasionally, some confusion in classification does occur in published literature. However, the objectives, underlying principles and technical requirements in hardware for HPLC and FIA are quite different. Although the two techniques have much to borrow from each other, they should rightfully belong to two different disciplines. 

In the classification scheme in Sec. 1.4.1, the first three entries under liquid-solid separation methods, i.e., ion-exchange, adsoiption, and sorbent extraction, all belong to column separation techniques. While in the batch approach, separations based on these principles may be performed either by static equilibration or by a column technique, online columns are invariably used in FI separations, both for convenience and efficiency. FI column separation systems based on different sorptive mechanisms do not differ strongly in the principles of system design and optimization of operational parameters. Therefore, the principles discussed in the following sections are generally applicable to the different approaches. 

Table 25,1 A broad classification of reaction-separation techniques and strategics...

McEwen et al. have utilized another ambient technique called atmospheric pressure solids analysis probe (ASAP) [84,85] and interfaced it with TWIM-MS [86], This source is now available commercially on the Synapt instrument. They have used m/z vi drift time plots to define compound classes in CTude oil analysis and to resolve isobaric compounds. Excellent agreement was demonstrated for drift times obtained from standards run individually and doped into the crude oil mixture. This work demonstrates the utility of mobility experiments to provide a degree of separation and classification in the study of very complex mixtures where chromatographic separation is either not possible or too time consuming. 

The success of an ISPR process does not depend only on the chosen separation technique but also on the configuration of the bioreactor/separation units and mode of operation. Previous reviews have shown the various possible modes of operation (continuous, batch) and the use of a separation unit outside of the reactor or separation techniques that act right inside the fermenter [19,22,31]. Freeman and coworkers introduced a classification scheme for ISPR process based on batch/continuous operation and internal (within the reactor)/external (outside the reactor) removal of the product [3]. 

Classification of the separation techniques according to those involving phase change or mass transfer from one phase to another, known as diffusional operations, and those that are useful in the separation of solid particles or drops of a liquid and that are generally based in the application of an external physical force, known as mechanical separations. 

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