Small scale preparations advantages

Mechanical stirring, although not essential for small scale preparations, is advantageous and increases the yield slightly. 

Chapter XII is concerned with Semimicro Technique. There can be little doubt that preparations on a smaller scale than has hitherto been customary have many advantages particular reference may be made to cost, time and bench space, all of which are important factors in teaching laboratories and also in training for research. Once the student has mastered the special technique, no difficulty should be experienced in adapting most of the preparations described in the book to the semimicro scale. A few examples of small-scale preparations are included together with a suggested list of experiments for an elementary course. 

Skraup reaction, 828, 829, 830, 991, 992 Small scale preparations, 1110-1114 advantages of, 1110, 1111 apparatus for, 1111 basis of an elementary course, 1111-1114... 

Thin-layer chromatography is frequently employed for following the course of chemical reactions and for small-scale, preparative purposes. Often, it may be advantageous to employ a fluorescent adsorbent and to use a p-toluenesulfonic ester instead of the corresponding methanesulfonic ester, since p-toluenesulfonic esters can then be located by examination of a chromatoplate under ultraviolet light. 

In these, the gas phase is suitably collected and subjected to the subsequent analytical determinations in a discontinuous fashion. Although the classical distillation systems have fallen into disuse since the advent of the advantageous gas chromatography, their automation has fostered the development of assemblies of some Interest. Chipperfleld et al. [2] reported a computer-controlled laboratory fractional column for small-scale preparations in which a microcomputer controls the column-jacket temperatures, boil-up rate and reflux ratio to achieve optimum separations. A schematic diagram of the dls-... 

Potable water (Tap water, Aqua, Aqua commimis, Water for human consumption) is as such a raw material for purified water in small-scale preparation and it may be used for the early stages of cleaning pharmaceutical equipment. It has the advantage that, if there is a good flow rate through the pipes, in most European countries it usually has a reasonable microbiological quality. 

One advantage of the method is that any impurities not converted to UV-absorbing derivatives are not detected, so cannot obscure the separations. On the other hand, it is likely again that the principal use of such methods will be for small-scale preparative separations of single components for structural analysis or for liquid scintillation counting. The technique may also prove invaluable for determination of the fatty acid composition of seed oils containing thermally labile fatty acids, such as those with cyclopropene moieties [987]. GC is likely to remain the method of choice for analytical... 

The conclusion was that fixed-bed reactors employing covalently immobilized enzymes are the most advantageous for repeated transformations because of increased enzyme stability, high coenz3nme turnover number [12], and satisfiujtory mass transfer rates. These two-phase reactors demonstrated that cofactor-dependent enzymes can be used in flow systems with no need for macromolecular coenzymes and appear to be the most suitable for scaling up. Free enzymes, which are easier to handle, are preferable for occasional use and small-scale preparations. 

Osmium tetroxide is the traditional osmium species used in the dihydroxylation of olefins. For large-scale reactions, osmium tetroxide may be weighed and transferred as the solid. For many catalytic applications on a laboratory scale, the amount of osmium tetroxide required is too small to be weighed conveniently. In these cases, advantage can be taken of the solubility of osmium tetroxide in organic solvents by the preparation of a stock solution of known concentration and the use of an aliquot for the small-scale reaction. 

As stated by Manz, the pTAS was envisioned as a new concept for chemical sensing, needed since sensors at that time were not providing the best results in terms of selectivity and lifetime. Initially, the main reason for miniaturisation was to enhance the analytical performance of the device rather than to reduce its size. However, it was also recognised that a small scale presented the advantage of a smaller consumption of sample and reagents. Moreover, the total chemical analysis system scheme could provide an integration of several laboratory procedures such as sample preparation, filtration, preconcentration,... 

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