Research titration curve

Fig. 16-4 pH sensitivity to SO4- and NH4. Model calculations of expected pH of cloud water or rainwater for cloud liquid water content of 0.5 g/m. 100 pptv SO2, 330 ppmv CO2, and NO3. The abscissa shows the assumed input of aerosol sulfate in fig/m and the ordinate shows the calculated equilibrium pH. Each line corresponds to the indicated amoimt of total NH3 + NH4 in imits of fig/m of cloudy air. Solid lines are at 278 K, dashed ones are at 298 K. The familiar shape of titration curves is evident, with a steep drop in pH as the anion concentration increases due to increased input of H2SO4. (From Charlson, R. J., C. H. Twohy and P. K. Quinn, Physical Influences of Altitude on the Chemical Properties of Clouds and of Water Deposited from the Atmosphere." NATO Advanced Research Workshop Acid Deposition Processes at High Elevation Sites, Sept. 1986. Edinburgh, Scotland.)... 

Figure 8.11. Titration curves of ai-acid glycoprotein (17 pM) (a) and of HSA (10.5 pM) (b) with calcofluor. Source Albani, J. R. and Plancke, Y. 1999. Carbohydrate Research. 318, 193-200.

Once titration curves have been measured using one of fhe above methods, they are typically fitted to Eq. (2) in the case of a single fifrafion, or to an equation describing the pH-dependence of fhe chemical shift due to two or more titrations. The overall goal of experimental measurements has hitherto been to extract pK values from titration curves, and the information published in research publications (the pKa values) are thus an interpretation of fifrafion curves and not the primary experimental data. 

Bowden, J. W., A. M. Posner, and J. P. Quirk. 1977. Ionic adsorption on variable charge mineral surfaces. Theoretical charge development and titration curves. Soil Research 15, no. 2 121-136. 

Figure 13 Spectrocoulometric titration of cytochrome c (17.5 iiM) and cytochrome c oxidase (6.3 )iM) by reduction with electrogenerated methyl viologen radical cation (MV +) at a SnOs OTE. Each spectrum was recorded after 5x10 equivalents of charge (0.5 mC) were passed. Spectra correspond to titration from totally oxidized to totally reduced forms. The final two spectra around 605 nm were recorded after excess MV + was present. Inset shows titration curves at 550 and 605 nm. Reprinted with permission from Heineman WR, Kuwana T and Hartzell CR (1973) Biochemical and Biophysical Research Communications 50 892-900.

The interpretation of the experimental results has not taken into account any kinetic effects, which might be of importance in this particular case of dynamic-operation. The results obtained here are therefore not exactly comparable to those carried out by a normal potentiometric titration. Nevertheless, the value of the buffer capacity at a certain pH contains quantitative information about the amount of protein that is present. Moreover, the curve as a function of the pH as shown in Fig. 16 reveals a protein signature that is specific for each different type of protein. This feature might be exploited in future biosensor research. 

Acid-base constants/proton-affinity constants These parameters cannot, at present, be established experimentally. Because there are probably several distinct sites and electrostatic effects, the overall surface-charge curves do not give any hint as to the nature and reactivity of these sites. Experimental back-titration data by Schulthess and Sparks [103], which indicate steps in the proton adsorption isotherm (i.e., the surface-charge density versus pH curve), were interpreted by these authors to be indicative of individual sites with individual reactivities. However, such data are not reproduced by the bulk of research groups. In the previous subsection, the back-titration technique has been discussed in some detail and, in particular, the results on goethite obtained with base titrations at low pH were found to show significant scatter compared to data obtained with the coulometric approach. 

Surface-active molecules or ions with an amphiphilic structure are known to have low solubility in water and self-assemble into large aggregates [61], According to the enthalpy curves presented in Fig. 6.30, surfactant aggregation may occur not only in aqueous solution but also at the Solid-Liquid interface. Since the topic of surfactant aggregation is a well-developed field of research [62, 71, 73, 93, 99, 100], only a brief review of the broad principles is proposed in the present paragraph to better illustrate the contribution of titration calorimetry. 

Several methods have been employed by various researchers to quantify the short-chain carboxylic acids and anions in solutions of geochemical interest. Before the advent of gas chromatography, many researchers used titrimetric methods to quantify CAA in formation waters. However, in practice, formation waters that contain high concentrations or complex mixtures of CAAs yield titrimetric results that are uninterpretable (e.g., a Gran Mals plot that yields a line rather than a set of curves with clearly defined titration inflection points). 

With the spectrum deconvolution analysis developed by Van Wielink et al. (1982) the spectra could be simulated by the dotted Gaussian curves. Also using the results of a potentiometric titration (not shown) the peaks are interpreted Sybesma, C. (ed.). Advances in Photosynthesis Research, Vol. II. ISBN 90-247-2943-2. 

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