High pressure ashing

Table 8.11 Main characteristics of high-pressure ashing...

Method development for high-pressure ashing and closed microwave digestion was reported for wet oxidation and extraction of Pb, Cd, Cr and Hg from various food packaging materials [57]. Use of HPA resulted in the highest median recoveries of the spiked elements (Pb and Cd, 92% Cr, 97% Hg, 83%). The use of In as an internal standard improved the accuracy... 

Two sets of bottles were kept at +6°C and +20°C during a period of 12 months and As, Hg and Se were determined to assess the possible losses of volatile compounds. Samples were digested by high-pressure ashing with a mixture of HNO3, HCl and H2SO4 at 320°C for 2 h. The final determination methods were HAAS (As, Se) and CVAAS (Hg). No instability could be demonstrated. 

High-Pressure Digestion, The introduction of a high-pressure ashing (HPA) technique by Knapp [45] has not only reduced the effective ashing time to ca. two hours but also opened the way to digestion of extremely resistant materials [46J. High-... 

Figure 31. High-pressure ashing apparatus HPA-S (Courtesy of Perkin Elmer)...

Zbinden, R, and Andrey, D. (1998). High pressure ashing—Determination of trace element contaminants in food matrices using a robust, routine analytical method for ICP-MS. Af. Spectrosc. 19(6), 214. 

Cleaning procedures include an internal washdown with a 0.5 to 2% soda ash solution, using a high-pressure jet. All wash water must be drained and deposits removed from the boiler. Usually, all external surfaces of the boiler are cleaned as well, in addition to the flue gas side of the economizer, air heater, and ID fans. 

Complete dissolution of plutonium residues, especially high temperature calcined plutonium dioxide contained in residues such as incinerator ash, continues to cause problems, despite continued research since the Manhattan Project (9). Methods to improve the Rocky Flats system include the use of additives (e.g., cerium) and electrochemistry, other solvents (HCl-SnCl2) as well as high-temperature fusion methods (10). High pressure dissolution, HF preleaching, fluorination, and other methods are being investigated. 

Numerous microwave applications have been published on decomposition, fusion, dry and wet mineralisation, ashing and extraction. Knapp et al. [67] have reported decomposition efficiencies of over 96% for PE, PVC, PS and PB, using PMD. Boron in polyolefins was determined after high-pressure microwave digestion followed by ICP-MS [80]. 

Fire For an infectious disease or weapon, use available methods and equipment on surrounding fires. Appropriate extinguishing agents dry chemical, soda ash, sand, or lime. Do not use high pressure water streams... 

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