Degradation Under Particular Conditions

Good thermal stability is a requirement for surfactants used in processes to enhance oil recovery. This applies most particularly to steam foam applications where surfactants such as AOS may be exposed to temperatures far above 100°C albeit for short times. Many authors have approached the problem of the thermal stability of a surfactant through a determination of the activation energy of the thermal degradation process. Once the activation energy is known, it can be used to estimate the rate of thermal degradation under various conditions. 

Certain classes of lipids are susceptible to degradation under specific conditions. For example, all ester-linked fatty acids in triacylglycerols, phospholipids, and sterol esters are released by mild acid or alkaline treatment, and somewhat harsher hydrolysis conditions release amide-bound fatty acids from sphingolipids. Enzymes that specifically hydrolyze certain lipids are also useful in the determination of lipid structure. Phospholipases A, C, and D (Fig. 10-15) each split particular bonds in phospholipids and yield products with characteristic solubilities and chromatographic behaviors. Phospholipase C, for example, releases a water-soluble phosphoryl alcohol (such as phosphocholine from phosphatidylcholine) and a chloroform-soluble diacylglycerol, each of which can be characterized separately to determine the structure of the intact phospholipid. The combination of specific hydrolysis with characterization of the products by thin-layer, gas-liquid, or high-performance liquid chromatography often allows determination of a lipid structure. 

In addition to the polymerase function of DNA Pol I the purified enzyme also possesses discrete 3 - 5 and 5 -> 3 exonucleolytic activities. Under particular conditions these activities degrade DNA strands with the release of 5 -mononucleotides (Fig. 1.3b.). 

Some approaches/examples for conducting forced degradation studies are given below For a forced degradation acid study for a particular API the API is exposed to acidic conditions. The API (at a known concentration) is usually prepared in the sample preparation solvent, which gives 0.1 M HCl concentration in the final solution. Once this solution is prepared, it is injected every half hour or hour to determine the loss of API over time. If the API is susceptible to degradation under acidic conditions, then peak(s) of degradation products would increase over time and the API should decrease over time... 

Refractoriness The resistance of a substance to degradation. Often applied to organic matter Relative humidity The ratio of the partial pressure of water to the saturation vapor pressure at that temperature Reservoir An amount of material defined by certain chemical, physical, or biological characteristics that, under particular conditions, can be considered as reasonably homogeneous... 

TNT degrades under aerobic conditions into monoamino-, diamino-, and hydroxylamino-DNT, and tetranitro-azoxynitrotoluenes. RDX and HMX degrade into carbon dioxide and water under anaerobic conditions. Researchers have not identified any specific organisms that are particularly effective for degrading explosives waste a consortium of organisms usually effects the degradation. 

Degradation under mild conditions in the presence of carbon monoxide is generally limited to compounds of the first row metals and, in particular, to nickel derivatives. This is probably due to the combination of a greater difference between the Ni-Ni and Ni-CO bond energies and the presence of holes in the... 

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