Buffering capacity citrate

Flue Ga.s Desulfuriza.tion. Citric acid can be used to buffer systems that can scmb sulfur dioxide from flue gas produced by large coal and gas-fired boilers generating steam for electrical power (134—143). The optimum pH for sulfur dioxide absorption is pH 4.5, which is where citrate has buffer capacity. Sulfur dioxide is the primary contributor to acid rain, which can cause environmental damage. 

The compact, nonporous anodic alumina film is the most suitable for fundamental investigations. It is grown by anodization, mostly under constant-current (galvanostatic) conditions, in neutral solutions of borates, tartrates, citrates, and phosphates, all of which possess significant buffering capacity and hence do not allow significant dissolution of the oxide. 

Buffers are used mainly to control the pH and the acid-base equilibrium of the solute in the mobile phase. They can also be used to influence the retention times of ionizable compounds. The buffer capacity should be maximum and should be uniform in the pH range of 2-8 commonly used in HPLC. The buffers should be soluble, stable, and compatible with the detector employed, e.g., citrates are known to react with certain HPLC hardware components. 

In principle, it would be logical to combine plots of the buffer index curves of each of the buffer components of milk and thus obtain a plot which could be compared with that actually found for milk. It is not difficult, of course, to conclude that the principal buffer components are phosphate, citrate, bicarbonate, and proteins, but quantitative assignment of the buffer capacity to these components proves to be rather difficult. This problem arises primarily from the presence of calcium and magnesium in the system. These alkaline earths are present as free ions as soluble, undissociated complexes with phosphates, citrate, and casein and as colloidal phosphates associated with casein. Thus precise definition of the ionic equilibria in milk becomes rather complicated. It is difficult to obtain ratios for the various physical states of some of the components, even in simple systems. Some concentrations must be calculated from the dissociation constants, whose... 

The eluents suitable for the separation of amino acids on latex cation exchangers do not comprise the classical citrate/borate buffers but mixtures of nitric acid and potassium oxalate. In comparison to buffers composed of sodium citrate and borate, these components may be obtained at much higher purity. The retention of the amino acids to be analyzed, however, is possibly affected by the sample pH due to the limited buffer capacity of the eluents that are based on nitric acid and potassium oxalate. Fig. 4-21 shows the separation of a calibration standard for collagen hydrolysates on an Amino Pac PA-1 latex cation exchanger at ambient temperature. The advantage is the short... 

The alteration of mineral and casein equilibria is reflected in changes to the physical properties of milk. The addition of citrate and different types of phosphates (ortho-, pyro-, or hexameta) to milk protein concentrate solutions, which alters the distribution of calcium and inorganic phosphate between the colloidal and serum phases of milk, affects its turbidity and buffering capacity (Mizuno and Lucey, 2005). The turbidity is affected because dissolution of colloidal calcium phosphate is accompanied by release of caseins into the serum. 

Acidity, alkalinity, buffer capacity, and pH are all related and are usually readily controllable within limits by the addition of reagents. The pH must generally be kept on the acid side to prevent alkaline degradation with the attendant development of bitterness and brown color. When this reaction takes place, the pH is slowly reduced by the acidic end products until a stable pH is reached. For practical purposes, products are available from pH 3.5 to 5.5 with any reasonable quantity of suitable edible buffer salts, such as acetate, lactate, and citrate. 

Thus, the combination of citrate buffering capacity and thiosulfate concentration provides capacity for short-term overloads of either sulfur dioxide or hydrogen sulfide. There is no need for precise instantaneous adjustment of the hydrogen sulfide flow rate to match exactly the instantaneous sulfur dioxide absorption rate. This is in contrast with the gas phase reaction where precise stoichiometry must be maintained at all times. 

A high buffering capacity of the solution is necessary to ensure a steady state process. For this reason acetate, citrate, propionate, glycolate, lactate, or amino-acetate is added to the solutions. These substances along with buffering may form complexes with nickel ions. Binding ions into a complex is required in alkaline solutions (here ammonia and pyrophosphate may be added in addition to citrate and amino-acetate). In addition, such binding is desirable in acid solutions... 

---