Acid-base buffer systems defined

The pH of the plasma may be considered to be a function of two independent variables (1) the PCO2, which is regulated by the lungs and represents the acid component of the carbonic acid/bicarbonate buffer system, and (2) the concentration of titratable base (base excess or deficit, which is defined later), which is regulated by the kidneys. The plasma bicarbonate concentration is generally taken as a measure of the base excess or deficit in plasma and ECF, although it is recognized tliat conditions exist in which bicarbonate concentration may not accurately reflect the true base excess or deficit. 

In order to be able to predict the retention behavior of peptides of different composition, of peptides of the same composition but different sequence (positional isomers), and of diastereoisomeric peptides, a knowledge of the incremental contribution of each amino acid to the overall contact area term is required not only for each well-defined stationary phase but also for each mobile-phase condition. Group retention coefficient summation approaches based on the assumption that selectivity differences can be ascribed predominantly to amino acid sequence differences, have been developed by Meek (46a, 52b) and Su et al. (45a). These treatments have subsequently been applied to a number of different elution systems (52c-52e). A comparative analysis of the different amino acid group contribution coefficients derived for phosphate, perchlorate, pyridine/acetate, trifluoroacetate, and bicarbonate buffer systems has been reported (52f). 

Obviously the buffer intensity can be expressed numerically by differentiating the equation defining the titration curve with respect to pH. For a monoprotic acid-base system (see equations 67 and 69). 

The concept of buffer intensity considered above may be extended and defined in a generalized way for the incremental addition of a constituent to a closed system at equilibrium. Thus, in addition to the buffer intensity with respect to strong acids or bases, buffer intensities with respect to weak acids... 

The poising (buffering) of a redox system against a pe change can be defined—similarly as in acid-base systems—as a redox-buffer or poising intensity... 

Buffers are defined as substances that resist changes in the pH of a system. All weak acids or bases, in the presence of their salts, form buffer systems. The action of buffers and their role in maintaining the pH of a solution can best be explained with the aid of the Henderson-Hasselbalch equation, which may be derived as follows. 

With pKa 7.2, it would appear that phosphate buffer is an excellent choice for buffering the blood. Although the blood pH of 7.4 is well within this buffer system s capability, the concentrations of H2P()4 and HP042 in blood are too low to have a major effect. Instead, the phosphate system is an important buffer in intracellular fluids where its concentration is approximately 75 mEq/L. Phosphate concentration in extracellular fluids such as blood is about 4 mEq/L. (An equivalent is defined as the mass of acid or base that can furnish or accept 1 mol of H+ ions. The abbreviation mEq indicates a milliequivalent.) Because the normal pH of... 

The second section is characteristic of the saturated solutions before the equivalence point and continues up to complete acid-base neutralization of the cation studied. A flat form of the potentiometric curve in this section is defined by the formation of a buffer system of composition oxide precipitate/solution of the cation possessing a higher buffer number than... 

A buffer is defined as a solution that resists change in pH when a small amount of an acid or base is added or when the solution is diluted. This is very useful for maintaining the pH for a reaction at an optimuiri vrdue. A buffer solution consists of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid at predetermined concentrations or ratios. That is, we have a mixture of a weak acid and its salt or a weak base and its salt. Consider an acetic acid-acetate buffer. The acid equilibrium that governs this system is... 

Acidity and alkalinity titrations determine the total capacity of natural waters to consume strong bases or acids as measured to specified pH values defined by the endpoints of titrations. Of more interest for many purposes is the ability of a water or water-rock system to resist pH change when mixed with a more acid or alkaline water or rock. This system property is called its buffer capacity. Buffer capacity is important in aqueous/environmental studies for reasons that include ... 

The units of OXC and RDC, as defined, are eq/L or meq/L. This makes OXC comparable to acidity and alkalinity, which are also given in eq/L or meq/L (Chap. 5). The pH buffer capacity measures the resistance of a system to pH change at a given pH, upon addition of a strong acid or base (Chap. 5). The concept of redox capacity, as proposed by Nightingale (1958) and defined above, is... 

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