Buffer anion, effect

The effect of buffer anions on peroxynitrite decomposition. As the concentration of formate is increased, the rate of peroxynitrite decomposition increases but reaches a plateau at high concentrations. The maximum rate depends on the pH. 

D. Effect of Buffer Cation and Buffer Anion The electroosmotic flow is proportional to the potential drop across the diffuse layer of counterions associated with the capillary wall. Because the potential drop is formed by counterions in the buffer attracted to the charged silica surface, the nature of the counterions will affect the zeta potential and therefore the EOF. Figure 4.5 shows the effect of the buffer cation on the mobility of both the EOF (using mesityl oxide as the marker) and a solute (dansylalanine).16 The highest mobility is obtained with the smallest cations however, high mobility may decrease solute resolution, so care must be taken in choosing the cation. The buffer anion also affects the mobility of the EOF, although trends are less apparent. Therefore, the effect of the EOF on a separation can be altered by careful selection of both the buffer anion and cation. 

If one compares two electrolyte solutions, a phosphate buffer solution and a KCl one with the same pH in the bulk solution, the pH at the electrode/ electrolyte interface in a phosphate buffer solution is actually lower than in a KCl one. Such a difference in the pH enhancement, depending on anions, leads to the anionic effect in CO, reduction, as discussed in Section VIII.3. 

Stationary phase-macromolecule repulsion is yet more evident in SEC of proteins on SW columns in sodium dodecyl sulfate (SDS), in which solvent strongly anionic protein-surfactant complexes are formed. A pronounced ionic strength dependence was observed (76) for the MW calibration curves obtained with a series of globular proteins in 0.1% SDS containing 0.02 M - 0.2 M pH 7 phosphate buffer. The effect of ionic strength on the shapes of these calibration curves is quite similar to observations with strong polyanions. The pronounced influence of I on Ksec °f proteins in SDS eluant was also observed by Takagi et al. (77). 

Citrate buffers are usually used as electrolytes for the electrodeposition of ZnTe [135-140]. Citrate can form complex ions with Zn ". Therefore, Zn " ions exist in the form of Zn(Cit)2" in citrate buffer solutions and Zn(Cit)2" ions are the species involved in reactions (31)-(34). The cathodic electrodeposition of ZnTe has been carried out using three kinds of citric acid electrolyte, each with a different counter anion (i.e., sulfate, chloride, and nitrate) to investigate the anion effect [139]. The authors reported that the type of anions affects the morphology, composition, and strucmre of the obtained ZnTe films. 

It is known that, with certain electron acceptors, the activity of sulfite oxidase is sensitive to inhibition by anions, such as phosphate (see Cohen and Fridovich, 1971). In keeping with this finding, Kessler and Rajagopalan (1974) reported anion effects on the form of the Mo(V) EPR spectra of sulfite oxidase. Phosphate, thiocyanate, fluoride, and sulfate produced particularly marked effects relative to, e.g., chloride or nitrate. These changes were seen in experiments at pH 7 but not at pH 9. Unfortunately, however, the spectral changes were not analyzed in detail. Their interpretation might be complicated by the superimposition of pH effects (Section 7.4) and anion effects. Phosphate buffers are susceptible to substantial decreases in apparent pH on freezing (Williams-Smith et a/., 1977), a factor not appreciated at the time the work was done. Clearly, further work on the various spectra from sulfite oxidase is required. ... 

The concentration of the metal ion can be controlled by adjusting the ratio of the concentrations of free ligand and metal chelate. If both species are present in appreciable amounts, moderate changes in either concentration have Httie effect on the ratio. The concentration of the metal ion can thus be buffered in a manner analogous to the buffeting of pH by the presence of a weak acid and its anion... 

The effect of concentration of cationic (cetylpyridinium chloride, CPC), anionic (sodium dodecylsulfate, SDS) and nonionic (Twin-80) surfactants as well as effect of pH value on the characteristics of TLC separ ation has been investigated. The best separ ation of three components has been achieved with 210 M CPC and LIO M Twin-80 solutions, at pH 7 (phosphate buffer). Individual solution of SDS didn t provide effective separation of caffeine, theophylline, theobromine, the rate of separ ation was low. The separ ation factor and rate of separ ation was increase by adding of modifiers - alcohol 1- propanol (6 % vol.) or 1-butanol (0.1 % vol.) in SDS solution. The optimal concentration of SDS is 210 M. 

As in the case of bromodeboronation, an increase in acetate buffer concentration reduced the rate, the biggest effect arising from the acid component, and again the effect of increasing the concentration of acetate could not be explained. Chelates produced large rate accelerations as with bromodeboronation and sodium fluoride similarly produced a very large effect, which was considered to be related to the stability of the tetrafluoroborate anion. 

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