Alkaline digestion

Usually prepared on the large scale by caustic soda fusion of sodium naphthalene-1-sulphonate, but can also be obtained by high-temperature alkaline digestion of... 

Concentrated waste solutions are obtained from spent metal plating baths and etchants. However, the majority of metal wastes are soflds or sludges obtained from the hydrolysis of metal-bearing solutions and industrial process effluents. Most of these water-insoluble wastes are composed of hydroxides or basic salts of the contained metals. Eor processing by hydrometallurgical routes the materials must be brought into solution usually by acid or ammoniacal or alkaline digestion. 

Method 3060A. Alkaline Digestion for Hexavalent Chromium. Available at http // www.epa.gov/epawaste/hazard/testmethods/sw846. Accessed June 2, 2013. 

Mussels and Oysters PFOS, PFHS, PFBS, Alkaline digestion Betasil C18 2 mM ammonium LC-(QqQ)- [157]... 

Because PFAs can bind tightly to protein, a new method was developed by applying a combination of alkaline digestion and solid-phase extraction to improve the extraction of various short-chained and long-chained per-... 

Soil, sediment and sludges (chromium(VI)) Alkaline digestion extraction using Na2C03 and NaOH UV-VIS No data 85-115% EPA 1997 (Method 3060A and 7196A)... 

A simple and rapid MW-assisted alkaline digestion procedure was developed in combination with high-performance liquid chromatography (HPLC)DUV postcolumn oxidationDCVDAFS detection for methyl-Hg determination in biological tissues [45]. The accuracy of the method was evaluated by the analysis of the BCR 463 Tuna Fish CRM. 

Dissolution and Extraction in General For the dissolution of fish tissues different procedures are reported. Acid or alkaline digestion or solvent extraction is usually used for the separation of Hg species from biological matrices [45, 46]. For the quantitative extraction of Hg, four methods were examined HC1 leaching, alkaline-methanol extraction with tetramethylammonium hydroxide (TMAH) and... 

Enzymatic digestion has some advantages over conventional sample pretreatment procedures based on acid or alkaline digestion thus, the former uses mild conditions as regards temperature and pH, which avoids potential analyte losses by volatilization or ohemical transformation to other species, and reduces the risk of contamination. In addition, the selectivity of enzyme catalysis is a powerful tool for distinguishing between fractions of elements associated with different components of the matrix as enzymes act on oertain ohemical bonds only. 

An alkaline digest must normally be desalted before the nucleotides can be successfully fractionated. This may conveniently be carried out by neutralising the digest with 6 N perchloric acid (10 min at 0°C) or Dowex 50 and spinning the solution clear in a bench centrifuge. 

In the classical procedure, scheelite was mainly processed by acid digestion while wolframite was dissolved by an alkaline digestion. The important solid, pure intermediate was, in both cases, tungstic acid, derived either directly or after several precipitation steps. Tungstic acid is formed by a precipitation, which is a more or less instantaneous process. Foreign ions present in solution during the precipitation are partly entrapped or coprecipitated and contaminate the tungstic acid. 

While the alkaline digestion of wolframite ores results in the formation of Mn(OH)2 (equation 1) in which Mn is divalent, the presence of Mn02 in the ore tailings is not surprising because the air oxidation of Mn(OH)2 is well known (5). Extensive observations of the dissolution behavior of the tungsten ore tailings indicate that it is not a simple acid dissolution but a redox reaction such as... 

United States Environmental Protection Agency, Alkaline digestion for hexavalent chromium , EPA Method 3060A, National Technical Information Service, Springfield, VA, 1996. 

Not aU the available methods extract the mercury species from solid samples (soil, sediment or biological material) with acceptable efficiency. The procedure giving the best recovery for methyl mercury from soil (95 4%) is the distillation method, and from fish tissue it is alkaline digestion using tetramethylammonium hydroxide with focused microwave power (95 to 105%). There is no standardized method to assess the extraction efficiency of a particular method, but several options are described in the subchapter on extraction efficiencies. 

Chemical treatment using acid or alkali can be applied to eliminate interfering substances. Acidic or alkaline digestion is often used during extraction. Chemical treatment with sulfuric acid or KOH can also be used in combination with other clean-up steps such as silica gel.5T55.137.138... 

The total nitrogen content of the nitrided samples was determined by titration with a sulphuric acid solution of the ammonia evolved upon alkaline digestion at 400°C with molten KOH [5]. Repeatability of this method was evaluated for an aluminum nitride standard, for which the variation coefficient established from three replicate measurements was equal to 4.0%. 

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