Stabilizers, commercial solutions

Economic Jispects. Sodium borohydride is produced ia large quantities mainly as powder and stabilized water solution. Potassium borohydride powder is produced ia lesser amounts. Commercial quantities of sodium borohydride powder sell for ca 55/kg (1992 price) the 12% solution ia caustic soda is priced at ca 47/kg of contaiaed NaBH. ... 

Dissociation of the second proton is insignificant. The pH of its aqueous solutions can be measured reproducibly with a glass electrode, but a correction dependent on the concentration must be added to obtain the tme pH value. Correction values for the most common commercial solutions are Hsted in Table 3. The apparent pH of commercial product solutions can be affected by the type and amount of stabilizers added, and many times the pH is purposely adjusted to a grade specification range. 

N-Acetylneuraminic acid aldolase (or sialic acid aldolase, NeuA EC 4.1.3.3) catalyzes the reversible addition of pyruvate (2) to N-acetyl-D-mannosamine (ManNAc (1)) in the degradation of the parent sialic acid (3) (Figure 10.4). The NeuA lyases found in both bacteria and animals are type I enzymes that form a Schiff base/enamine intermediate with pyruvate and promote a si-face attack to the aldehyde carbonyl group with formation of a (4S) configured stereocenter. The enzyme is commercially available and it has a broad pH optimum around 7.5 and useful stability in solution at ambient temperature [36]. 

The class I FruA isolated from rabbit muscle aldolase (RAMA) is the aldolase employed for preparative synthesis in the widest sense, owing to its commercial availability and useful specific activity of 20 U mg . Its operative stability in solution is limiting, but the more robust homologous enzyme from Staphylococcus carnosus has been cloned for overexpression [87], which offers unusual stability for synthetic purposes. Recently, it was shown that less polar substrates may be converted as highly concentrated water-in-oil emulsions [88]. 

Sodltsn perborate, dispersed In water, enhances the degradation rate of phosphorus esters. It owes Its reactivity to hydroperoxyl anion, a powerful nucleophile, which Is produced by dissociation of FB In aqueous solution. Because of Its stability, commercial availability, and great reactivity we recommend PB as a detoxicant for hazardous OF wastes. 

Antibody stability in solution cannot be predicted without thorough stability studies technicians are advised to follow proper quality control procedures for stability validation if primary antibodies are to be diluted in the laboratory and utilized for extended periods of time. An advantage to using commercially diluted primary antibodies is the built-in customer protection provided by the regulatory mandates that govern reagent manufacturers. Manufacturers must demonstrate the stability of commercially produced reagents for defined periods to establish a predictable shelf life for their antibody products. 

Stabilized hypochlorite solutions, commercially available, are satisfactory. The submitters used 1.15 1. of Clorox solution, containing 5.25 per cent sodium hypochlorite by weight. 

Homogeneous solutions are the preferred formulation systems for parenteral administration because they can be easily visually inspected for the absence of particulate matter. For this reason, cosolvent solubilization is the first choice for parenteral products once purely aqueous systems provide insufficient solvency. The compositions of three commercial, injectable products are given in Table 39.5. The first product (1) has a low percentage of cosolvent in the separate solvent ampoule. The drug substance is provided as a dry powder because of its limited stability in solution. The second one (2) is solubiUzed with two cosolvents amounting to 50% of the total volume, whereas in the third product the drug dose is dissolved in a water-free mixture of cosolvents. This draws the attention to a further point to consider when cosolvents are employed in formulations. The formulation has to be devised such that the effect of dilution of... 

Lv et al. have demonstrated the ability of the microemulsions to improve the hydrolytic stability of a known anti-microbial agent chloramphenicol [5]. The components of mi-croemulsion included IPM, Tween 20 and Span 20, which have good ocular acceptability. The accelerated stability studies on chloramphenicol microemulsions and commercial solution were carried out for 3 months demonstrated significantly lower hydrolysis of chloramphenicol (14.38%) as compared to that of solutions (27.11%). H NMR studies on microemulsions confirmed that the chloramphenicol was embedded in the surfactant chains that may provide higher stability. 

Conventional MAO has very low solubility in aliphatic solvents as well as poor storage stability in solution, which considerably limits its utility. Other more soluble and commonly used aluminoxanes are ethylaluminoxane and isobutylaluminoxane, which are synthesized by the partial hydrolysis of triethyl-aluminum (TEA) and triisobutylaluminum (TIBA), respectively. However, these alkylaluminoxanes do not perform as well as MAO in metallocene-mediated olefin polymerization. " It was reported, however, that tetrakis(isooctyl) alumoxane [(i-octyl)2—O—Al-(i-octyl)2], prepared by reaction of Al(i-octyl)3 with 0.5 equiv of water, exhibits remarkable cocatalytic activity, comparable to or even greater than that obtained with MAO, for ethylene polymerization catalyzed by racemic an5a-bis(indenyl)-type zir-conocene dichlorides. Furthermore, commercial modified methylaluminoxanes (MMAO) available from... 

For reasons outlined above, deltamethrin in commercial solutions contains the radical scavenger 2,6-dimethyl, 4-t butylphenol. For other proposals for stabilizations see Sect. B.3.4.2 Vol. 4 of this series. 

A still unanswered problem with POMs is related to the inherent acidity of these catalysts and the use of aqueous H2O2 as the oxidant (the commercial solution is acid stabilized), as they may cause hydrolysis of the epoxide. Many approaches such as the addition of basic pH-adjusting additives,insufficient amount of aqueous H202, the use of phase transfer catalysts and organic solvents have... 

The use of formaldehyde to stabilize PAA solutions has been documented in previous sections. With the later discovery that low molecular weight alcohols also stabilize polyacrylamide solutions, the question arose as to the effect of methanol that is always present in commercially available formaldehyde solutions. It seemed possible that the methanol was solely responsible for the stabilizing effect by commercial formaldehyde. 

The methyl alcohol generally present in commercially available formaldehyde solutions was not a significant beneficial factor in the ability of formaldehyde to stabilize PAA solutions. 

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