Decomposition of biological materials

The state of the art for the decomposition of biological materials are the ashing methods. Of course, some of these methods stiU have teething troubles. TTie most recent include the following techniques and devices ... 

Kotz, L., Kaiser, G., Tschopel, P. and Tolg, G. (1972) Decomposition of biological materials for the determination of extremely low contents of trace elements in limited amounts with nitric acid under pressure in a Teflon tube. Fresenius Zeitschrift fur Analytische Chemie 2 60(3), 207-209. 

Wiirfels, M., Jackwerth, E. Investigations on the carbon balance in decomposition of biological materials with nitric acid. Fresenius Z. Anal. Chem. 322, 354-358 (1987)... 

Pilz W, Komischke S. 1972. [The determination of vanadium in biological material and in the air. 2. Decomposition of biological material, air analyses]. International Journal of Environmental Analytical Chemistry 1 275-282. (German)... 

Figure 6 shows schematically the aquatic redox cycle of iron. Under the conditions usually encountered in natural aquatic systems, the reduction of iron(III) is accompanied by dissolution and the oxidation of iron(II) by precipitation. Reductive dissolution of iron(III) hydroxides occurs primarily at the sediment-water interface under anoxic conditions in the presence of reduct-ants, such as products of the decomposition of biological material or exudates of organisms. Reductive dissolution of iron(III) hydroxides, however, can also occur in the photic zone in the presence of compounds that are metastable with respect to iron(III), that is, compounds that do not undergo redox reactions with iron(III) unless catalyzed by light. The direct biological mediation of redox processes may also influence the redox cycles of iron (Arnold et al., 1986 Price and Morel, Chapter 8, this volume). Dissolved oxygen is usually the oxidant of... 

Kotz etal. (1972, Decomposition of biological materials for the determination of extremely low contents of trace elements in limited amounts with nitric acid under pressure in a Teflon tube) Hartstein et al. (1973, Novel wet-digestion procedure for trace-metal analysis of coal by atomic absorption) Jackson etal. (1978), Automated digestion and extraction apparatus for use in the determination of trace metals in foodstuffs) Campos etal. (1990, Combustion and volatilization of solid samples for direct atomic absorption spectrometry using silica or nickel tube furnace atomizers) Erber et al. (1994, The Wickbold combustion method for the determination of mercury under statistical aspects) and Woit-tiez and Sloof (1994, Sampling and sample preparation). 

Knapp, G. (1988). New developments in the decomposition of biological material, Trace Elem. Anal. Chem. Med. Biol., Proc.Int.Workshop, 5th, 63-71. Ed. by Braetter, P. and Schramel, P.de Gruyter Berlin, FRG... 

Wurfels, M. and Jackwerth (1985). Investigations of the carbon balances in decomposition of biological materials with nitric acid, Fres. Z. Anal. Chem. 322,35-58 Yin, D. and Wang, Y. (1987). Analytical problems of trace elements In biological materials. Part 2. Sources of analytical errors in trace element analysis of biological materials, Zhong. Huan. Hexue 7(2), 67-71... 

Other than grooving, localized attack due to ammonia is relatively rare. Patches of attack can occur in conjunction with biological fouling emd decomposition of organic materials, which generate ammonia. 

Parnas, H. 1975. Model for decomposition of organic material by microorganisms. Soil Biology and Biochemistry 7 161—169. 

A managed process that controls the biological decomposition of biodegradable materials into a humus-like substance called compost The aerobic and mesophilic and thermophilic degradation of organic matter to make compost the transformation of biologically decomposable materials through a controlled process of bio-oxidation... 

According to Stoeppler et al. [15], severe errors up to a factor of two may result from ETA—AAS analysis of biological materials without some form of sample pretreatment. The approaches that will be discussed here are (a) the use of diluent solutions to minimise matrix and molecular absorption interferences (b) partial decomposition techniques in which metals are extracted from proteins with acids (c) dissolution of tissue samples without complete oxidation (d) complete oxidation procedures such as dry ashing, wet digestion at ambient and elevated pressures, and low temperature ashing with reactive gases at low pressures. 

It is of great importance to distinguish between enzymic and non enzymic LPO processes, in order to recognize whether a process is a physiological one, induced by enzymes, or is the result of processing of biological material in aqueous solution which induces by decomposition of LOOHs nonenzymic LPO processes as well. 

Several different processes have been proposed for the conversion of solid organic wastes to a more usable liquid or gaseous form to be utilized as fuel or petrochemical feedstocks. Principally the commonly discussed processes involve the biological conversion to alcohols, the catalytic chemical conversion to methanol or Fischer-Tropsch liquids via a carbon monoxide and hydrogen synthesis gas, or the thermochemical formation of gases or oxygenated liquids by pyrolysis. Pyrolysis is defined as the decomposition of organic material at elevated temperatures. The process to be described uses a very special case of pyrolysis. 

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