Costs chemical separation methods

The ideal chemical separation method should be relatively simple, have few separation stages and should be time / cost effective. Itoh et al (2002) used a combined anion and cation exchange column method for the isolation of Ca from other alkaline earth metals. This 3 column separation involved 6 chemical separation techniques following two HF/HCIO4 digests. The decontamination factors for Eu and Co are quoted as >10. The final limit of detection for " Ca for this method was 8 Bq/g, based on a measurement by X-ray spectrometric determination. 

The importance of chemical syntheses of a-amino acids on industrial scale is limited by the fact that the standard procedure always yields the racemic mixture (except for the achiral glycine H2N-CH2-COOH and the corresponding amino acid from symmetrical ketones R-CO-R). A subsequent separation of the enantiomers then is a major cost factor. Various methods for the asymmetric synthesis of a-amino acids on laboratory scale have been developed, and among these are asymmetric Strecker syntheses as well. ... 

When investigating the suitability of a particular resin-bound separations process, the following factors are often important (i) resin consumption (ii) solvent usage (iii) productivity-chemical, optical and volume yields (iv) total number of separations steps and (v) capital costs. For any particular process, these factors differ in their relative importance. However, when evaluating a new separations method it is useful to examine each of these factors. The nonchromatographic separation method... 

Solid phase spectrophotometry proved to be an appropriate technique for the determination of colorants in foods dne to its simplicity, selectivity, reasonable cost, low detection limits, and use of conventional instrnmentation. This simple, sensitive, and inexpensive method allowed simnltaneons determinations of Snnset Yellow FCF (SY), Quinoline Yellow, and their nnsnlfonated derivatives [Sndan I (SUD) and Quinoline Yellow Spirit Soluble (QYSS)] in mixtnres. Mixtnres of food colorants containing Tartrazine, Sunset Yellow, Ponceau 4R, Amaranth, and Brilliant Blue were simultaneously analyzed with Vis spectrophotometry without previous chemical separation. ... 

Chemical esterification methods use an alcohol and a carboxylic acid in the presence of a mineral acid as catalyst. Sulfuric acid, which is commonly used, leads to the formation of undesirable byproducts, requiring a difficult separation step (3). Moreover, in this case, the starting material is a high-value component (fatty acid). Consequently, researchers are interested in the alcoholysis reaction using a vegetable oil with low cost and largely produced in Brazil as a raw material for ester synthesis. 

Burton and Elad" in an investigation of a natural product introduced a new method of osmate cleavage. A solution of the olefinic product and osmium tetroxide in dioxane was let stand for 48 hrs. and hydrogen sulfide was passed in to precipitate hlack osmium dioxide this was removed by filtration and the diol recovered from the filtrate. An application of this procedure impressive for the scale on which costly chemicals were expended is reported by Hirschmann et al. of Merck in the synthesis from prednisone (I) of A-norcortisol (9), which proved to be devoid of physiological activity. A solution of 100 g. of prednisone BMD (2) in 720 ml. of pyridine was cooled to 5° and treated with a solution of 69.9 g. of osmium tetroxide (l.l X theoryI) in 40H ml. of pyridine. Black material began to separate in 5 min. After. 5 days at room temperature the reuclion mixture was stirred into 13.4 I. of petroleum ether and the precipitate was collected, washed, and dissolved in 8 I. of dioxane. The solution was cooled In an ice bath and saturated with hydrogen sulfide. The precipitated osmium dioxide was removed, and the bulk of the solvent removed... 

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