Acid studies degradation conditions

The photocatalytic activity of ZnO nanomaterials for the degradation of some organic pollutants in water [173] (e.g., dyes [174]) was explored by several groups to achieve environmental benefits. Recent studies have indicated that ZnO can be used under acidic or alkaline conditions with the proper treatment [175,176]. ZnO nanomaterials were used as photocatalysts for the degradation of phenol [177] and chlorinated phenols such as 2,4,6-trichlorophenol [178]. ZnO nanomaterials were also used for the degradation of Methylene Blue [179], direct dyes [180], Acid Red [181], and Ethyl Violet [182],... 

Healy and Young (58) observed that the conversion of vanillic and ferulic acids under anaerobic conditions to methane and CO2 was nearly stoichiometric. More than half of the organic carbon could potentially be converted to methane. This could have great importance in studies where the degradation of phenolic compounds are studied by trapping the evolved CO2. Under anaerobic conditions, part of the normal CO2 evolution may be shifted to methane production with a subsequent low reporting of CO2 evolved, and an underestimation of microbial activity in the soil (51). 

In our studies on the lignin peroxidase catalyzed oxidation of veratraldehyde and veratric acid no degradation was observed under the reaction conditions used. However, ligninolytic cultures of P. chrysosporium degraded veratraldehyde and veratric acid via reduction to veratryl alcohol... 

Much has been written about the effects of processing, temperature, and storage conditions on the stability of ascorbic acid in citrus juices. On the other hand, little is known about the stability of folic acid under similar conditions. Chen and Cooper (72) studied the effects of temperature and oxygen and ascorbic acid on the thermal degradation of folic acid, and they reported that ascorbic acid increased the stability of the terra-... 

The presence of acidic degradation products of both TBP and CMPO (HDBP, compounds (1) and (5)—strong extracting agents) was responsible for the dramatic elevation of DAm at low acidities. Specific studies have indicated that HDBP could increase americium extraction even for such small amounts as 5 x 10-2 mol L 1 (41), and that DAm depends on phosphinic acid (1) concentration to the power of three (40). The increase of DAm measured at low acidity under dynamic conditions compared to static radiolysis has been attributed to the formation of larger amounts of acidic degradation products, such as (1) and (2) (46). 

Some of these processes can be controlled and used for the preparation of chemicals of industrial interest, such as 5-(hydroxymethyl-2-furaldehyde, HMF). HMF is the product of a triple dehydration of fructose, which is itself one of the first degradation products of sucrose. The preparation and the uses of HMF have been extensively studied and reviewed by Lichtenthaler.342 It can be obtained under various degradative conditions, including acid catalysis and catalysis by lanthanide ions.343 Processes for the production of HMF on the multi-ton scale have been developed as well as many uses, notably polycondensations.344,345 The polymerization of HMF has been shown to produce complex... 

The temperature/humidity conditions used may be more severe than the typical accelerated stability testing conditions in order to generate potential degradation products in a reasonable time. The typical forced degradation conditions include thermolytic, hydrolytic, oxidative, photolytic (in excess of ICH conditions), high pH (alkaline conditions), and low pH (acidic conditions). Outlined in Table 9-25 and Table 9-26 are some solid-state and solution forced degradation studies, respectively, that could be conducted. In the following... 

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... 

Furaldehyde and reductic acid are formed by acidic treatment of hexuronic acids. Under special conditions, reductic acid is obtained as the major product. These reactions have been studied by Stutz and Deuel, who discussed a mechanism for the formation of the two compounds that involved splitting between C-5 and C-6 by decarboxylation. There is, at present, insufficient evidence to permit formulation of any mechanism for the degradation of the keto-n-glucosides. However, it is the writer s opinion that a ring closure between C-6 and C-2 in the common enediol derived from either the 2-keto or 3-keto compounds is po ible. In a pre-... 

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