Small-scale extractions

Fig. 4.3-33. SITEC super-critical fluid extraction small-scale plant [50].

First carry out a small-scale test, placing about 0 5 g. of the mixture in a test-tube, adding about 5 ml. of 10% aqueous NaOH solution, and shaking the mixture well. It will be readily seen whether the neutral substance (which remains undissolved) is solid or liquid. Then repeat the extraction on a largo scale as follows ... 

Biopolymer Extraction. Research interests involving new techniques for separation of biochemicals from fermentation broth and cell culture media have increased as biotechnology has grown. Most separation methods are limited to small-scale appHcations but recendy solvent extraction has been studied as a potential technique for continuous and large-scale production and the use of two-phase aqueous systems has received increasing attention (259). A range of enzymes have favorable partition properties in a system based on a PGE—dextran—salt solution (97) ... 

Other Methods. Instant tea may also be prepared by directiy extracting fermented leaf before the firing stage. These processes, only suited for practice in the tea-growing countries, have been carried out on a small scale in Sri Lanka, India, and Kenya (101). 

Scandium is very widely but thinly distributed and its only rich mineral is the rare thortveitite, Sc2Si20v (p. 348), found in Norway, but since scandium has only small-scale commercial use, and can be obtained as a byproduct in the extraction of other materials, this is not a critical problem. Yttrium and lanthanum are invariably associated with lanthanide elements, the former (Y) with the heavier or Yttrium group lanthanides in minerals such as xenotime, M "P04 and gadolinite, M M SijOio (M = Fe, Be), and the latter (La) with the lighter or cerium group lanthanides in minerals such as monazite, M P04 and bastnaesite, M C03F. This association of similar metals is a reflection of their ionic radii. While La is similar in size to the early lanthanides which immediately follow it in the periodic table, Y , because of the steady fall in ionic radius along the lanthanide series (p. 1234), is more akin to the later lanthanides. 

The use of mercury for extracting precious metals by amalgamation has a long history and was extensively used by Spain in the sixteenth century when her fleet carried mercury from Almaden to Mexico and returned with silver. However, environmental concerns have resulted in falling demand and excess production capacity. It is still used in the extraction of gold and in the Castner-Kellner process for manufacturing chlorine and NaOH (p. 72), and a further major use is in the manufacture of batteries. It is also used in street lamps and AC rectifiers, while its small-scale use in thermometers, barometers and gauges of different kinds, are familiar in many laboratories. 

The substances involved in bioluminescence reactions are usually unstable. Thus, the extraction and purification of bioluminescent substances should be carried out in the shortest possible period of time, usually at a low temperature. It is known through experience that luminescent substances are almost always more stable in the original animal tissues than in extracts when preserved at a low temperature. Therefore, before starting extraction and purification, the stability of the extracts and purified substances should be investigated by carrying out a small-scale pilot experiment. A pilot experiment is also essential in the course of purification to avoid an unexpected loss of the target substance. If a component of the luminescence system is insoluble in common buffer solutions, it must be solubilized to purify it (see C1.3). 

At atmospheric or reduced pressure, a melt polymerization on a small scale (25-100 g) can easily be carried out using straight-wall flange flasks (250 mL) (Fig. 3.18a). The straight wall often allows the extraction of the polymer from... 

Fig. 11 Experimental set-up for small-scale microwave SPPS of /S-peptides (SPE = solid-phase extraction). 1 Pasteur pipet for N2 agitation 2 10 mL glass vial 3 4mL solid-phase extraction tube 4 DMF 5 coupling solution 6 resin 7 polyethylene frit 8 Luer-lock cap...

The demand for metallic Sr and Ba is severely limited. Consequently, they are speciality products and are extracted from their ores in small-scale batch processes. 

Economic feasibility studies suggest that even at the present state of the art photocatalytic technology indeed can be competitive with the traditional carbon adsorption or incineration technologies in treatment of contaminated soil vapor extraction vents and small scale VOC-containing vents [28]. Rapid progress in basic and applied research in photocatalysis suggests... 

Cane sugar is processed using one of two methods of extraction. One method uses diffusion and the other uses roller press extraction. Both methods may be used to make sugar and molasses fractions from sugarcane. However, roller press extraction is used by a greater percentage of the industry and, therefore, is the better method for a small-scale study. 

In proper experimentation important considerations are the chemical nature of the analyte and the proposed analytical technique for further analysis of the extract. When a modifier is used it is best to use the modifier solvent as the trapping solvent. A disadvantage of solid-based traps is that most subsequent separation techniques (e.g. GC or HPLC) require a solution consequently, it is then necessary to carry out a (small scale) solvent extraction to remove the analytes from... 

A procedure for preparation of sodium hyponitrite involving reduction of nitrogen oxide by the ketyl, followed by extraction into water [1], had been operated routinely on the small scale. A 41-fold scaled up run exploded and ignited after 200 ml of water had been added as part of the work-up. This was attributed to the presence of an unusually large proportion of coagulated unreacted sodium in the ketyl. Small-scale operation with precautions is urged [2],... 

Reaction is terminated by acetonitrile quenching, or by liquid-liquid extraction with water-immiscible organic solvent, provided that the extraction efficiency and the effect of the organic solvent on product stability are tested at the small scale. Based on properties of product, the pH of the reaction mixture should be adjusted before termination to allow maximal recovery of the product. For example, acid is usually added to the acyl-glucuronide product mixture at the end of the reaction to minimize acyl migration. 

Small-Scale Extraction of PHA from Transgenic Plants. 227... 

One of the more important considerations in determining the end use of synthetic graphite is its contamination with metallic components Metals such as iron, vanadium, and especially in nuclear applications, boron are deleterious to the performance of graphite Table 3 presented the extraction yields of NMP-soluble material for three bituminous coals. For these coals, mineral matter and insoluble coal residue were separated from the extract by simple filtration through 1-2 pm filter paper fable 13 lists the high-temperature ash content in the dry coal, and in their corresponding NMP-insoluble and NMP-soluble products. The reduced ash content of the extract is typically between 0.1 to 0.3 wt% using traditional filtration techniques for the small-scaled extraction experiments... 

Most studies of micellar effects upon rates or products of organic reactions have been made with very low concentrations of reactants, and this small scale of work is not very encouraging for the synthetic organic chemist. An additional disadvantage is that surfactants complicate product separation by extraction or distillation, and to date most studies in this general area have been exploratory and have been aimed at solving these problems. 

Reliable mechanistic conclusions require high intrazeolite yields that account for the majority of the substrate mass balance. This can be a challenge because of the small-scale reactions often conducted for mechanistic studies. In addition, rapid removal of the products from the zeolite, and/or low conversions to decrease residence time, is occasionally necessary because of the sensitivity of the reaction products to the zeolite environment.44,45 Intrazeolite products are generally recovered by extractive techniques from either the intact zeolite, or from a mixture formed after mild digestion of the zeolite. Polar solvents such as tetrahydrofuran or acetonitrile coupled with a continuous extraction technique is in particular an effective means to remove polar products with an affinity for the interior of the zeolite.44 Zeolite digestion with mineral acids, in order to liberate the products, must be conducted with care in order to prevent acid catalyzed product decomposition or reaction.46,47... 

Recently an isotope dilution method has been reported O for assaying neomycin sulphate. However, it is first necessary to prepare 14C-labelled neomycin sulphate. This is accomplished by adding l4C-labelled glucose to a small-scale fermentation of 5. nad-iat. l4C-labelled neomycin can then be extracted by solvent-extraction or by ion-exchange chromatography. 

Unfortunately, the appeal of solid phase extractions on small scale fades as the scale increases due to the cost and inconvenience of using large amounts of fluorous silica gel. Here, modified techniques to reduce the tedium of repeated extractions are attractive. For example, Crich has recently introduced the minimally fluorous selenide C6Fi3CH2CH2C6H4SeH[171. This selenol is added in catalytic quantities to tin hydride reductions of reactive aryl and vinyl radicals. The high reducing capacity of the aryl selenide suppresses undesired reactions of product radicals without suppressing the reactions of the aryl and vinyl radicals themselves. After the reaction is complete, the selenol can be recovered by a modified continuous extraction procedure. 

We usually conduct solid phase extractions on small scale and have not focused on the recovery of the tin reagents. However, in principle this should be possible for many types of reactions. 

In theory, such information could be extracted from high-resolution experimental data. However, due to the technical challenges, conditional statistics of small-scale quantities are more readily accessible from numerical simulations. 

In this chapter the three main modes of large-scale chromatographic operation, and combined reaction and separation. Many useful but small-scale chromatographic methods have been omitted, as well as allied separation techniques which combine aspects of chromatographic principles or practice with aspects of adsorption, extraction, sedimentation or electrophoresis. Such is the pace of invention that novel processes related to chromatography are still being developed and described in the literature. 

For example, copper is about 99% pure after extraction. This copper is pure enough for some uses, such as the manufacture of copper pipes for plumbing. However, the copper is not pure enough for one of its principal uses, electrical wiring. Therefore, some of the impure copper is refined electrolytically, as shown in Figure 11.25. Nickel can be refined electrolytically in a similar way. You refined copper on a small scale in Investigation 11-C. 

Bunzl, K., Schimmack, W., Belli, M., and Riccardi, M., 1997, Sequential extraction of fallout radiocesium from the soil Small scale and large-scale spatial variability. J. Radioanal. Nucl. Ghent. 226 47-53. 

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