Buffers effectiveness

A fourth alkalinity control additive is magnesium oxide [1309A8A], which is used in clay-free polymer-base fluids (47). Magnesium oxide provides an alkaline environment and, as it is only slightly soluble, also has a buffering effect. It enhances the thermal stabHity of polymer solutions by preventing a pH decrease to neutral or slightly acidic conditions at elevated temperatures. It is mainly appHed in completion or workover operations where clay-free acid-soluble fluids are desired. 

Thermal stabihty of the foaming agent in the presence of high temperature steam is essential. Alkylaromatic sulfonates possess superior chemical stabihty at elevated temperatures (205,206). However, alpha-olefin sulfonates have sufficient chemical stabihty to justify their use at steam temperatures characteristic of most U.S. steamflood operations. Decomposition is a desulfonation process which is first order in both surfactant and acid concentrations (206). Because acid is generated in the decomposition, the process is autocatalytic. However, reservoir rock has a substantial buffering effect. 

In Cosmetics. Amino acids and their derivatives occur in skin protein, and they exhibit a controlling or buffering effect of pH variation in skin and a bactericidal effect (216). Serine is one component of skin care cream or lotion. Ai-Acylglutamic acid triethanolamine monosalt is used for shampoo. Glucose glutamate is a moisturizing compound for hair and skin (234). 

Consequently, biochemists conducting in vitro experiments were limited in their choice of buffers effective at or near physiological pH. In 1966, N.E. Good devised a set of synthetic buffers to remedy this problem, and over the years the list has expanded so that a good selection is available (Figure 2.18). 

Antonenko et al. [540] considered pH gradients forming in the UWL under bulk solution iso-pH conditions. They elegantly expanded on the buffer effect model and made it more general by considering multicomponent buffer mixtures. Direct measurements of the pH gradients (using wire-coated micro-pH electrodes) near the membrane-water interface were described. 

You might be wondering why the bicarbonate buffer can buffer effectively at pH 7.4 when its pKa is 6.1. The answer is that it doesn t buffer all that well. What makes it unique and the major buffer system of the blood is that C02, being a gas, can be exhaled by the lungs. Exhaling C02 is equivalent to exhaling protons. 

Strong electrostatic interactions with ionic metal complexes can only occur when this buffering effect of the oxide is overcome. 

We have seen that a BGE for analysis of anions and organic acids needs to have (a) a pH above the p A 2 of the analyte, (b) a sufficient buffering effect, and (c) a co-ion as a probe for indirect UV detection, with mobility close to that of the analytes of interest. Furthermore, care should be taken to reverse the EOF of the capillary and to work in the anodic or reverse mode. 

Since food has a buffering effect, antacids are taken between meals (e.g., 1 and 3 h after meals and at bedtime). Nonabsorbable antacids are preferred. Because Mg(OH)2 produces a laxative effect (cause osmotic action, p. 170, release of cholecystokinin by Mg, or both) and Al(OH)3 produces constipation (cause astringent action of AP, p. 178), these two antacids are frequently used in combination. 

Due to their high concentration, plasma proteins—and hemoglobin in the erythrocytes in particular—provide about one-quarter of the blood s buffering capacity. The buffering effect of proteins involves contributions from all of the ionizable side chains. At the pH value of blood, the acidic amino acids (Asp, Glu) and histidine are particularly effective. 

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