Sequestering agent function

Various polyphosphates are effective sequestering agents under appropriate conditions. The best known of these is sodium hexametaphosphate (10.14), the cyclic hexamer of sodium orthophosphate. Further examples are the cyclic trimer sodium trimetaphosphate (10.15), as well as the dimeric pyrophosphate (10.16), the trimeric tripolyphosphate (10.17) and other linear polyphosphates (10.18). All of these polyanions function by withdrawing the troublesome metal cation into an innocuous and water-soluble complex anion by a process of ion exchange as shown in Scheme 10.7 for sodium hexametaphosphate. Hence these compounds are sometimes referred to as ion-exchange agents. 

Mitochondria are distinct organelles with two membranes. The outer membrane limits the organelle and the inner membrane is thrown into folds or shelves that project inward and are called cristae mitochondriales. The uptake of most mitochondrion-selective dyes is dependent on the mitochondrial membrane potential. Conventional fluorescent stains for mitochondria, such as rhodamine and tetramethylrosamine, are readily sequestered by functioning mitochondria. They are, however, subsequently washed out of the cells once the mitochondrion s membrane potential is lost. This characteristic limits their use in experiments in which cells must be treated with aldehyde-based fixatives or other agents that affect the energetic state of the mitochondria. To overcome this limitation, the research... 

Casein may be coagulated and recovered as rennet casein by treatment of milk with selected proteinases (rennets). However, one of the caseins, K-casein, is hydrolysed during renneting and therefore the properties of rennet casein differ fundamentally from those of acid casein. Rennet casein, which contains the colloidal calcium phosphate of milk, is insoluble in water at pH 7 but can be dissolved by adding calcium sequestering agents, usually citrates or polyphosphates. It has desirable functional properties for certain food applications, e.g. in the production of cheese analogues. 

Figure 5 Calculated theoretical for sorption of uranyl onto a goethite substrate as a function of pH at fixed total carbon concentration in the presence of a sequestering agent (EDTA). are shown for several levels of calcium concentration. Surface area of the substrate is 100 L total carbon is fixed at 1.5 X 10 M and total uranium...

Studies on the aerobic oxidation of sucrose with noble metal catalysts revealed low selectivity and, surprisingly, the involvement of all of the three primary alcoholic functions at Cg, Ci, and Cg while preserving the disaccharide backbone (Figure 21.12). This is not a problem, because mono- and polycarboxylated sugars are both economically attractive as biodegradable calcium sequestering agents ... 

Zeolites have similar chemical compositions to minerals. Both natural and synthetic zeolites exist. Not only do zeolites find extensive use as catalysts in industry they can also function as ion-exchange matrices. There are several recent reports [16] of the use of zeolites in this capacity much of the work concentrates on zeolites in washing powder where they remove calcium and magnesium from water. Zeolites replaced polyphosphates as calcium and magnesium sequestering agents due to the unacceptable phosphate-promoted eutrophication of lakes. 

A whole range of inorganic and organic bases can be used to adjust the pH of NR field latex. However, ammonia remains the most common and the cheapest option and hence is widely used. Additional preservatives are sometimes used to further boost the stability of NR latex concentrates. Very often they function as bactericides, enzyme inhibitors, sequestering agents or stabilizers and are often used in combination. Some early preservative systems that were discontinued mainly because of safety and health hazard concerns are 0.2% sodium penta-chlorophenate and 0.2% ammonia 0.1% sodium pentachlorophenate and 0.1% ethylenediaminetetraacetic acid (EDTA) and 0.1% ammonia 0.2% zinc di-ethyldithiocarbamate (ZDTC) and 0.2% ammonia 0.2% boric acid, 0.05% ammonium laurate and 0.2% ammonia. 

The preservatives may function as bactericides, enzyme inhibitors, sequestering agents or stabilizers. They are often used in combination. A system widely used today is zinc oxide/TMTD 0.025% lauric acid or ammonium laurate 0.05% and ammonia (NH3) 0.2%. This is the low ammonia LA-TZ centrifuged latex corresponding to Type III. 

Product A has been shown to exhibit excellent wetting properties and, due the increased solubility and free carboxyl group, has the potential to act as a calcium sequestering agent while the aldehyde function of product B is a likely starting point for further chemical derivatization [24]. 

Uses Designed for prevention and removal of metal oxide deposits In aq. systems contains sequestering agents, org. dispersants, and surf. act. agents to provide detergency at solld/llq. Interface, to Inc. removal of deposits will function at near neutral pH... 

Syn. Cleansers Cleaning Agents G. Reiniger F produits i nettoyer There are numerous household, institutional and industrial c. available, which have multipurpose or specific functions. The products are formulated from many ingredients, but the most important are - surfactants and sequestering agents. The use of RR-based products is rather limited. 

Builders impart the function of complexing and sequestering, mainly Ca-ions in the water used (hardness), from soil and from the fiber surface. The only RR-based sequestering agents are - citric acid and citrates, but they are of increasing importance. 

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