Complexing agents, degradation

Considerable effort has been directed to the degradation of complexing agents. The degradation of nitrilotriacetate (NTA), ethylenediamine tetraacetate (EDTA), and related compounds display some important featnres ... 

Pirkanniemi, K., Complexing Agents A Study of Short-term Toxicity, Catalytic Oxidative Degradation and Concentrations in Industrial Waste Waters. Kuopio University Publications C. Natural and Environmental Sciences, 209, 2007, Doctoral dissertation. Finland. 

Complexing agent that deactivates or reduces the ability of metal ions to initiate or to catalyze the degradation of a polymer. 

On the other hand, many excipients can act to chemically stabilize an API in the solid state and in solid dosage forms. The most common class of stabilizing excipients is cyclodextrins (36). Cyclodextrins can envelop the API in their hydrophobic cavities and shield it from common degradation reactions such as hydrolysis, oxidation, or photodegradation. Some excipients or additives may also act as complexing agents that provide hydrolytic (37) and oxidative (38) stabilization. Many excipients, such as cyclodextrins, dyes, and colored additives, are capable of providing extensive photostabilization in the solid state (39-41). 

Sample containers must be suitable for storage without degradation especially when acids are added to liquid samples. The absorption of radionuclides from solution is less on polyethylene than on glass. With a few exceptions, almost all sorption losses can be eliminated by the addition of acid, a carrier solution containing stable elements, or a complexing agent. 

Some pertinent degradants from glass are silica lamination, especially in phosphate buffer after 6 or more months of stability. Citrate and EDTA can induce complexing agents as well as high levels of sodium, aluminum, barium, and iron. 

Cyclodextrins are degradation products from starch by the bacterium Bacillus macerans. They are separated by precipitation with complexing agents and purified by recrystallization. They could probably be produced industrially by the tonne. The formation of cyclodextrins is interpreted as a trans glycosidation of amylose under enzymic control. The latter, in aqueous solution, adopts at least partially the shape of a helix with a period of six glucopyranose units. The bacterial enzyme catalyses the junction of two glucopyranose residues separated... 

Ruthenium tetroxide was shown to oxidize PCBs in water [20], Water-soluble ruthenium complexes, such as [Ru(H20)2(DMS0)4]2+, are effective catalysts for the KHSO5 deep oxidation of a number of chloroaliphatics, of a-chlorinated al-kenes, polychlorobenzenes, and polychlorophenols. When the reactions are carried out in water in the presence of surfactant agents, degradation of the substrates is definitely faster. Aromatic substrates are mainly converted into HC1 and C02, polychlorophenols being more sensitive to oxidation than substituted benzenes [21]. Replacement of the DMSO- solvated ruthenium by RuPcS results in a definite improvement of the reaction course with hydrogen peroxide, since dismutation of... 

This compound is the most widely-used of the family of aminopolycarboxylic acids, which act as strong metal ion-complexing agents. Its near-ubiquity in surface waters has begun to cause concern. OH-induced degradation represents one way to cope with this problem. Radiolytic studies focusing on the action of OH have been undertaken recently [54, 55]. 

Many complexing agents are hardly degradable and therefore can be observed in environmental waters. Since the complexing agents such as ethylenediamino tetra-acetic acid (EDTA), nitrilo triace tic acid or aminophosphonic acids are extremely polar compounds, they were determined preferentially by ESl-LC-MS. IC interfaced by ESI to the MS allowed the determination of EDTA in pg L quantities without any pre-concentration [397]. Metal complexes of EDTA were very stable and could be observed after ESI-LC-MS as [M-i-metal] ions in positive ionisation mode [398]. ESI CE-MS was applied to separate and to quantify the stabile Ni-EDTA complexes [399]. 

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