Influence of ionic strength

This experiment describes the determination of the stability (cumulative formation) constant for the formation of Pb(OH)3 by measuring the shift in the half-wave potential for the reduction of Pb + as a function of the concentration of OH . The influence of ionic strength is also considered, and results are extrapolated to zero ionic strength to determine the thermodynamic formation constant. 

Fig. 23. Influence of ionic strength of solution (p) on precipitation of serum albumin by /)FAV-17and2)FAV-16microdispersions.CSA = 10-4 mol/l,CCp = 0.09mg/ml,pH = 6.2...

Influence of ionic strength on the reaction rate constant. The influence of the ionic strength on the reaction rate constant was studied using KCl as electrolyte. The results obtained in this study are listed in Table 4, where we can see that the reaction rate constant for N-Br-alanine decomposition undergoes an increment of 40 % upon changing the ionic strength from 0.27M to IM, while in the case of N-Bromoaminoisobutyric acid the increment of the reaction rate constant is of about 12 %. This is an evidence of a non ionic mechanism in the case of the decomposition of N-Br-aminoisobutyric acid, as it is expected for a concerted decarboxylation mechanism. For the decomposition of N-Br-proline the increase on the reaction rate constant is about 23 % approximately, an intermediate value. This is due to the fact both paths (concerted decarboxylation and elimination) have an important contribution to the total decomposition process. 

Garcia, R., Porcar, I., Campos, A., Soria, V. and Figueruelo, J. E., Solution properties of polyelectrolytes. X. Influence of ionic strength on the electrostatic secondary effects in aqueous size-exclusion chromatography, /. Chromatogr. A, 662, 61, 1994. 

Electrostatic effects other than ionization are also important. Interactions between reacting ions depend on the local electrical environment of the ions and thus reflect the influence of the dielectric constant of the solvent and the presence of other ions and various solutes that may be present. In dilute solutions the influence of ionic strength on reaction rates is felt in the primary and secondary salt effects (see below). 

Equation 7.1.2 characterizes what is known as the primary salt effect (i.e. the influence of ionic strength on the reaction rate through the activity coefficients of the reactants and the activated complex). Much early work on ionic reactions is relatively useless because this effect was not understood. Now it is common practice in studies of ionic reactions to add a considerable... 

The influence of ionic strength on the two rate constants was noted to be as follows. 

Small TD, Warren LA, Ferris FG (2001) Influence of ionic strength on strontium sorption to bacteria, Fe(III) oxide and composite bacteria-Fe(III) oxide surfaces. Appl Geochem 16 939-946... 

The electrophoretic mobilities of cationic analytes in water, in non-aqueous methanol and acetonitrile were measured and the influence of ionic strength and ion-pair formation on the mobility was determined. It was assumed that the mobility n of the ion at infinite dilution (jxQ ) and the viscosity of the pure solvent are constant ... 

S.P Porras, M.-L. Riekkola and E. Kenndler, Electrophoretic mobilities of cationic analytes in non-aqueous methanol, acetonitrile and their mixtures. Influence of ionic strength and ion-pair formation. J. Chromatogr.A 924 (2001) 31 12. 

The oxidative behaviour of glycolaldehyde towards hexacyanoferrate(III) in alkaline media has been investigated and a mechanism proposed, which involves an intermediate alkoxide ion. Reactions of tetranitromethane with the luminol and luminol-peroxide radical anions have been shown to contribute substantially to the tetranitromethane reduction in luminol oxidation with hexacyanoferrate(III) in aerated aqueous alkali solutions. The retarding effect of crown ethers on the oxidation of triethylamine by hexacyanoferrate(III) ion has been noted. The influence of ionic strength on the rate constant of oxidation of ascorbic acid by hexacyanofer-rate(III) in acidic media has been investigated. The oxidations of CH2=CHX (where X = CN, CONH2, and C02 ) by alkaline hexacyanoferrate(III) to diols have been studied. ... 

Vasilev, V. P. Influence of ionic strength on the instability constants of complexes. Russ. J. Inorg. Chem., 1962, 7, 8, 924 927. 

Although these effects are often collectively referred to as salt effects, lUPAC regards that term as too restrictive. If the effect observed is due solely to the influence of ionic strength on the activity coefficients of reactants and transition states, then the effect is referred to as a primary kinetic electrolyte effect or a primary salt effect. If the observed effect arises from the influence of ionic strength on pre-equilibrium concentrations of ionic species prior to any rate-determining step, then the effect is termed a secondary kinetic electrolyte effect or a secondary salt effect. An example of such a phenomenon would be the influence of ionic strength on the dissociation of weak acids and bases. See Ionic Strength... 

A.V. (1997) Adsorption of a corticoid on colloidal hematite particles of different geometries. J. Colloid Interface Sd. 187 429-434 Verdonck, L. Hoste, S. Roelandt, F.F. Van der Kelen, G.P. (1982) Normal coordinate analysis of a-FeOOH - a molecular approach. J. Molecular Structure 79 273-279 Vermilyea, D.A. (1966) The dissolution of ionic compounds in aqueous media. J. Electro-chem. Soc. 113 1067-1070 Vermohlen, K. Lewandowski, H. Narres, H-D. Schwager, M.S. (2000) Adsorption of polyelectrolytes onto oxides - the influence of ionic strength, molar mass and Ca " ions. Coll. Surf. A 163 45-53... 

FIGURE 2.13 Influence of ionic strength on solute retention. Analytes 1, uracil 2, phenol 3, procaine 4, propranolol 5, toluene. Column Symmetry RP C8 150 x4mm. Mobile phase methanol-phosphate buffer pH 7 upper chromatogram ImM lower chromatogram 20mM. 

Kadima, W.L. Ogendal, R., Bauer, N., Kaarsholm, K., Brodersen, Hansen, J.F., Porting, P. (1993). The Influence of ionic strength and ph on the aggregation properties of zinc-free insulin studied by static and dynamic laser light scattering. Biopolymers, 33, 1643-1657. 

The influence of ionic strength on yCii is great in solvents of lower permittivities. When we compare ionic activities in different solvents, we have to consider this activity coefficient, in addition to the transfer activity coefficient yt. However, in reality, the influence of is usually negligibly small compared to that of yt. 

To summarize, there is still a need for carefully determining more rate constants for various substances of biological interest in their various charged forms. This phase of the subject will be complete when critically chosen values have passed into the Tables and when theoretical correlations have been sufficiently developed to enable rate constants for unexamined substances to be reliably predicted. There is also still a need to correlate the reactivity of the hydrated electron with the reactivity of free radicals such as H, OH, organic radicals, peroxy radicals, etc., so as to be able to predict the reactivity of unexamined free radicals. Another need is to establish the influence of conditions on the rate constants. The influence of ionic strength is now well known, but other factors, such as the dielectric properties of the medium, have been shown to have an effect in some cases (2, 20). Also, the effect of temperature has been investigated in only a few cases (9). 

Carr, M. E., Kaminski, M., McDonagh, J., and Gabriel, D. A. (1985). Influence of ionic strength, peptide release, and calcium ion on the structure of reptilase and thrombin-derived gels. Thromb. Haemost. 54, 159-165. 

In general, restricted hypertonic junctions can introduce EMF errors due to protein contamination (amorphous or precipitate overcoats) and isotonization of the junction with a subsequent influence of ionic strength. Open junctions, on the other hand, are apparently affected by the ionic form of proteins. The problem of reference electrode stability is especially important in direct measurements, as discussed above and elsewhere [9,33]. 

For the above reasons, the IFCC recommendations on activity coefficients [19] and the measurement of and conventions for reporting sodium and potassium [21] and chlorides [25] by ISEs were developed. At the core of these recommendations is the concept of the adjusted active substance concentration (mmol/L), as well as a traceable way to remove the discrepancy between direct and indirect determinations of these electrolytes in normal sera. Extensive studies of sodium and potassium binding to inorganic ligands and proteins, water binding to proteins, liquid-junction effects and the influence of ionic strength have demonstrated that the bias between sodium and potassium reports obtained from an average ISE-based commercial... 

Special software was introduced into EEPROM of the Microlyte 6, thus it is called Microlyte Mg, to compensate for calcium interference, the influence of ionic strength and to compensate for liquid junction potential changes, known to influence the quantitative reports on ionized magnesium [3]. 

To measure the influence of ionic strength, 30mmol/L of NaCl was added to the Cal 1 and measured with four instruments. 

Pacheco, A.C.C. and Torem, M.L. (2002) Influence of ionic strength on the removal of As5 + by adsorbing colloid flotation. Separation Science and Technology, 37(15), 3599-610. 

One approach (Melander, 1977) treats the protein as a dipole and applies the Kirkwood equation (Kirkwood, 1943), which attributes the influence of ionic strength to both electrostatic and hydrophobic forces [Eqs. (8.63) or (8.64)]. 

The comparison of CMC data in distilled vs. hard river water shows that the decrease in CMC with hardness has the order anionics cationics nonionics (Rosen et al., 1996). Hardness increases the dependence of the CMC on alkyl carbon chain length of CnE0mS04, indicating that in hard water the influence of additional carbon atoms is the same for CnE0mS04 as for CnEOm surfactants (Rosen et al., 1996). The influence of ionic strength on micellization of nonionic surfactants is due to a salting out effect of the hydro-phobic moiety of the surfactant molecule (Carala et al., 1994). 

The influence of ionic strength on surfactant sorption is shown in Fig. 2. In general, SDS sorption at 0.1 M NaCl was greater than for no added NaCl, consistent with previous observations (Xu and Boyd, 1995). Increased SDS sorption at the higher ionic strength can be explained by a decrease in the electrostatic repulsion between sorbed SDS molecules as well as between... 

Fig. 14. Influence of ionic strength on mobility w0, mobility at y = 0 u, mobility at a given y x, monovalent ions , divalent ions , trivalent ions. See reference A8.

Fig. 15. Influence of ionic strength on migration velocity. The velocity increases with decreasing ionic strength, but fractionation is impaired (barbiturate buffer).

Figure 16.4 Influence of ionic strength on the aggregates formation between BSA (6.1 x 10 mM) and oligomeric procyanidins from grape seed (O.lOmM) (in 12% aqueous ethanol, 0.1 M acetate buffer, pH 5.0) [78].

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