Purification methods before

Instead of specific amplification of one target to improve sensitivity, methods that amplify all genomic DNA or mRNAs are useful when the target is in short supply. For example, multiple-displacement amplification uses exonuclease-resistant random hexamers and a highly pro-cessive polymerase to amplify DNA nonspecificaily. Initial DNA denaturation is not necessary and the reaction proceeds isothermally. Similarly, messenger RNA can be generi-caUy amplified with a poly(T) primer modified with an RNA polymerase promoter. After reverse transcription, second-strand DNA synthesis, and transcription, antisense RNA is produced. Both whole genome and antisense RNA amplification are also useful as nucleic acid purification methods before amplification or detection. 

Analysis of zinc solutions at the purification stage before electrolysis is critical and several metals present in low concentrations are monitored carefully. Methods vary from plant to plant but are highly specific and usually capable of detecting 0.1 ppm or less. Colorimetric process-control methods are used for cobalt, antimony, and germanium, turbidimetric methods for cadmium and copper. Alternatively, cadmium, cobalt, and copper are determined polarographicaHy, arsenic and antimony by a modified Gutzeit test, and nickel with a dimethylglyoxime spot test. 

Methods of Purification. Although carbon dioxide produced and recovered by the methods outlined above has a high purity, it may contain traces of hydrogen sulfide and sulfur dioxide, which cause a slight odor or taste. The fermentation gas recovery processes include a purification stage, but carbon dioxide recovered by other methods must be further purified before it is acceptable for beverage, dry ice, or other uses. The most commonly used purification methods are treatments with potassium permanganate, potassium dichromate, or active carbon. 

Almost all the entries in Chapters 4, 5 and 6 have CAS (Chemical Abstract Service) Registry Numbers to identify them, and these have been entered for each substance. Unlike chemical names which may have more than one synonymous name, there is only one CAS Registry Number for each substance (with only a few exceptions, e.g. where a substance may have another number before purification, or before determination of absolute configuration). To simplify the method for locating the purification of a substance, a CAS Registry Number Index with the respective page numbers has been included after the General Index at the end of the book. This will also provide the reader with a rapid way to see if the purification of a particular... 

After the release of the oligosaccharides, they must be purified by a variety of methods before structural analyses can be undertaken. Ion-ex-change chromatography, gel-filtration chromatography, or some type of electrophoresis is usually used for the purification. At this point, structural analyses may begin. 

Biomass-derived gasification gas contains tar that can plug the particulate filters, and ammonia that forms nitrogen oxides when burned. The use of a catalytic gas purification unit before particulate filters to decompose tar and ammonia is a promising method to solve these problems,... 

The advantage of this screening method over other approaches is the elimination of purification steps before mass spectrometric identification. Also, the disadvantages associated with chromatographic separations are eliminated. However, the use FTICR mass spectrometric screening restricts the binding... 

This study emphasizes the measurement procedure of Sr activity in radioactive aqueous waste produced by the nuclear industry. Considering radioecological and radioprotective elements, there is a need for systematic measurements of Sr activity in rejected wastes. The classical methods for this determination are gas flow proportional counting, liquid scintillation counting or Cherenkov counting.These techniques require efficient concentration and purification steps before the measurement of radiostrontium itself. 

Table 3 Recovery rates of the sodium cations with different analytical methods before and after dialysis purification...

Preliminary extraction of 5-HIAA may be used as an initial purification step before HPLC analysis. Organic solvents, anion-exchange resins, and other solid phase extraction procedures have aU been used. For many systems, direct injection of urine onto the analytical column is a common practice,and samples are often merely diluted with a buffer to protect the HPLC system from contamination. Methods that analyze 5-HIAA without prior sample cleanup rely on the selectivity of the HPLC separation combined with fluorescence or electrochemical detection to provide the requisite specificity. 

Example 3 uses whole-broth-ethyl acetate extraction with solvent swing by pH adjustment. Solutes must be either weak acids or weak bases that can be extracted in or out of solvent by adjusting pH above or below the pKa of the solute. Since solutes may be unstable at extreme pH values, it is important to determine stability with small samples before using this method. This procedure IS the purification method used commercially for many antibiotics, with penicillin being the most widely studied example. Figure 3 shows the large changes of the distribution coefficient of penicillins and its impurities as a function of pH. Since any water-immiscible solvent can be used in this procedure, and because there are several interdependent parameters involved (partition coefficient, selectivity, emulsion tendency, separation characteristics), solvent... 

Another purification method consists in dissolving the crude material acid in water in a supercritical or subcritical state, and recrystallizing. A two-stage condensation process is simpler, in which an oligomer is produced that is purified before the second condensation to the high molecular product. ... 

Before analysis by HPLC can be performed, an initial sample purification is often necessary. Various purification methods for leukotrienes have been described in the literature. Depending on the type and size of the sample, and whether a total analysis is intended or if only certain components should be analyzed, different procedures can be used. The cysteinyl-containing leukotrienes are somewhat acid labile and require mild conditions for extraction and purification. A first extraction of leukotrienes from biological samples can be achieved by adsorption to some resin, e.g. Amberlite XAD-8 or XAD-7, at slightly acid or neutral pH [64,91,112,215] or adsorption to charcoal [75,118] or to Sephadex LH-20 [69]. Mild extraction into organic solvents at low temperature has also been used for cysteinyl-containing leukotrienes [119], although this method has preferably been used at a later step in the purification procedure for these compounds [75],... 

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