Titration profile

Case 3 No complexation. If the binding interaction is not strong enough there is no effect on the fluorescence. The fluorescence intensity of solutions of piperazinyl derivative 5a does not change on addition of metal ions. Ca(II) and Al(III), both very weak binders to the macrocyclic polyamines,(n) have no effect on the fluorescence of any anthrylazamacrocycle. Na+ also has no effect, and as shown in Figure 3.8 the titration profile of 5c with Zn(II) is virtually unaffected even by the presence of a 100,000-fold excess ofNa+ at pH 12. 

Figure 5 RP-HPLC Analysis of the Oxidation Reaction Mixtures for the Formation of Disulfide-Bridged Homo- (a) and Heterostranded (b) Coiled Coils and Gdn-HCl Titration Profiles of the Coiled Coils (c)P8] J>.c,d...

Figure 1 shows a comparison of the model results with the experimental results. The three curves shown in the plot correspond to three different values of the rate constant for the HOSO + O2 reaction upper - 8 x 10-13, middle - 4 x IO13, and lower - 2 x 10"13 cm3/s. Similar comparisons between model and experimental results have been made for a wide variety of other experimental conditions. Based upon such comparisons, we have concluded that a rate constant of (4 )x lu-13 cm3/s gives the best match between the experimental and model results, in both an absolute sense and based upon the shape of the O2 titration results. Since there is greater uncertainty in the absolute concentrations of HO radicals than there is in the trend of the HO concentrations with increasing O2, the comparison of the shapes of the experimental and model O2 titration profiles may provide a reliable basis for comparison. 

The conversion from abstract to chemical factors is sometimes called a rotation or transformation and will be discussed in more detail in Chapter 6, and is illustrated in Figure 4.9. Note that factor analysis is by no means restricted to chromatography. An example is the pH titration profile of a number of species containing different numbers of protons together with their spectra. Each equilibrium species has a pH titration profile and a characteristic spectrum. 

As previously reported for dicopper complex of cage compound 45 [79], the steric constraints imposed by the polycyclic framework induce clear selectivity effects in the recognition of ambidentate anions. In particular, spectrophotometric titration studies have shown that the [Cu 2(45)] + receptor gives 1 1 complexes of varying stability with ambidentate anions in aqueous solution. Also the [Zn 2(44)] + complex, which is stable in aqueous solution over a substantial range of pH, can encapsulate ambidentate anions, to give stable 1 1 inclusion complexes. In particular, by titrating with a standard solution an aqueous solution lO M in [Zn 2(44)] + complex buffered at pH 8, a linear decrease of fluorescence is observed until the addition of 1 equiv. of azide. From the titration profile, a value of log A" of 5.8 can be calculated for the inclusion equilibrium. 

With automation, the Karl Fisher titration provides a titration kinetics profile (e.g., milliliters of titrant vs. time). If the rate of water release from the solid is the rate-limiting step, the kinetics of the Karl Fisher titration profile can provide indirect information about the state of water associated with the solid. Fig. 14 shows the titrations of two different samples of dicaldum phosphate dihydrate. Here, and in the titration profiles in Fig. 15, the data have been normalized in such a way that each titration ultimately consumes 25 mL of reagent. This normalization is... 

The titration profiles for dicalcium phosphate are not monotonic, but exhibit stages of dehydration consistent with the scheme shown in Eq. (7). It is also evident that the release of moisture is faster from the milled form (Fig. 14, curve B) of the excipient. This is consistent with the increased total surface area and shorter diffusional path expected with smaller particle size. 

Titration profile of acetic acid (CH3COOH) with sodium hydroxide (NaOH). Maximum buffering capacity is at pH = pK, at which point minimal change in pH occurs upon addition of acid or base. 

Titration profiles of the basic and acidic amino acids lysine and aspartic acid are shown in Figures 2-9 and 2-10. The R-groups are ionized at physiological pH and have anionic and cationic groups, respectively. The pi value for aspartic acid is the arithmetic mean of pKj and pK2, whereas for lysine and histidine the pi values... 

At pH 9, the titration was limited to -565 mV, as shown in the right panel of Fig. 4 (B), and essentially only the first half of the titration profile that was observed at pH 10 was obtainable. At any given potential more positive than -560 mV, that portion of the iron-sulfur proteins that was not titrated i.e., not chemically reduced) could be reduced photochemically, but apparently only to the extent of further reducing FeS-A [see Fig. 4 (B) right panel]. Note that the g=1.89 line belonging to FeS-B was unaffected by illumination. These observations suggest that FeS-A, with its more positive redox potential, is the... 

Figure 12 Fluorosensing of transition metals by the tripodal tri-hydroxamate system 8. Spectrofluorimetric titration by standard base of 8, in aqueous MeOH diamonds 8 plus excess acid full triangles 8 , plus 1 equiv. of Fe " and excess acid open triangles 8, plus 1 equiv. of Cu and excess acid full diamonds 8 plus 1 equiv. of Ni" and excess acid. Co" and Fe" do not modify the titration profile obtained with 8 alone (open diamonds).

Figure 14 Fluorescence enhancement associated to Zn" coordination to 4. Full triangles refer to the spectrofluorimetric titration by standard base in aqueous MeCN of the two-component system 4, plus 1 equiv. of Zn and excess acid the titration profile obtained for a metal-free solution (open-triangles) is reported for comparative purposes. Coordination to Zn", a pH > 4.5, interrupts the eT process from the amine group adjacent to the fluorophore and awakens the fluorescence.

Figure 7.33 ITC binding experiments showing the affects of L-lysine and AMPPCP binding to LysU in the presence of Mg + and K+ ions, (a) Calorimetric titration profile deriving from the titration of LysU (6/.tM monomer) with injected aliquots of L-lysine in buffer pH 8.0 at 20°C in the presence of 10 mM MgCl2 (upper trace control titration in absence of LysU). (b) Heat absorbed per mole of L-lysine titrant versus [L-lysine]/[LysU monomer], (c) Calorimetric titration profile deriving from the titration of LysU (20 /xM monomer) with injected aliquots of /S,y-methylene ATP (AMPPCP) in buffer pH 8.0 at 20°C in the presence of ImM L-lysine, 10 mM MgCl2 (d) Heat absorbed per mole of L-lysine titrant versus [AMPPCP]/[LysU monomer] (adapted from Hughes et al., 2003, Fig. 3).

From the potentiometric titration, a break point at 2.0 equivalents of added base was observed, as shown in Fig. 3. The titration profile revealed that [( -C4H9)4N]4[a-PWii A1(0H2) 039] had two titratable protons dissociated from the AI-OH2 group. This result was consistent with the elemental analysis result. 

We know that HCl is a considerably stronger acid as compared to CH COOH. HCl ionizes fully and almost all the hydrogen of HCl is present as H at any point of time. HCl also conducts the electric current much better than CH COOH. The two acids, however, have similar titration profiles. 25 ml of 0.01 N NaOH are required to fully titrate 25 ml of 0.01 N HCl. The same amount of O.OllVNaOH is required to fully titrate 25 ml of O.OIN CH COOH. Both acids give similar titration response because of the following scheme of events. Acetic acid is weakly ionized and only 1.3% of its hydrogen is present as H. When we add alkali to this solution, the OH ions liberated from it combine with the H present and remove them in the form of water. 

The two acids therefore end up giving similar titration profiles. The acidity measured by titration is known as the total or the tltratable acidity and reflects the concentration of an acid in solution. It does not, however, reflect the strength of an acid or its actual acidity. 

Fig. 40 Titration profile of interacting solutions of the two biopolymers recorded at 20 °C. The titration was performed from pH = 10 towards lower pH values. The ehange in turbidity was observed at pH, pH and pHp p. The first appearance of turbidity seen at pHc is indicated as a change in the slope of turbidity versus pH curve (RejHoduced with permission from American...

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