Influence of Organic Solvents

Another reason for the apparent neglect of organic sample ions in conventional ion chromatography is the success of ion-pair methods for determination of organic ions. Ion-pair methods are discussed in Chapter 9. 

The ion-exchange process in aqueous systems has already been described in Sections 3.2 and 3.3. When adding organic solvents to the mobile phase, the complexity of this process increases, because several competing parameters determine the retention characteristics. 

Selectivity is influenced by the type and concentration of the organic solvent The type of organic solvent is an important factor in optimizing separation, because the solvation power and hydrophobicity of the solvent influence the retention mechanism. Investigations of the influence of various organic solvents 

flow rate 2 mL/min detection phosphate (6), and 15 mg/L sulfate (7). 

---

Of course, the influence of organic solvents on enzyme enantioselectivity is not limited to proteases but it is a general phenomenon. Quite soon, different research groups described the results obtained with lipases [28]. For instance, the resolution of the mucolytic drug ( )-trans-sobrerol (11) was achieved by transesteriflcation with vinyl acetate catalyzed by the lipase from Pseudomonas cepacia adsorbed on celite in various solvents. As depicted in Scheme 1.3 and Table 1.5, it was found that t-amyl alcohol was the solvent of choice in this medium, the selectivity was so high ( >500) that the reaction stopped spontaneously at 50% conversion giving both +)4rans-sobrerol and (—)-trans-sobrerol monoacetate in 100% optical purity [29]. 

Silva C, Matama T, Guebitz G M et al (2005) Influence of organic solvents on cutinase stability and accessibihty to polyamide fibers. J Polym Sci A Polym Chem 43 2749-2753 Crouzet J, Faucher D, Favre-Bovine G, Jourdat C, Petre D, Pierrard J, Thibault J, Guitton C Enzymes and micro organisms with amidase activity which hydrolyze polyamides. US Patent 6180388... 

Other electrochemical processes of organic compounds on Pb electrodes or electrodes with UPD Pb have been studied - formaldehyde [323], oxalic acid [386], trichloro- and trifluoroethane [387], 1-phenylethylamine [388], 3-hydroxychi-nuclidine [388], dichlorodifluoromethane [389], polychlorobenzenes [390], 1-propa-nol [391], pyrrole polymerization [392], and inorganic compounds - phosphine [388] and sulfate(IV) ions [393]. Simultaneous catalytic or inhibiting influence of organic solvents - acetonitrile, dimethyl-sulfoxide, and Pb + presence on electrooxidation of small organic molecules on Pt electrodes has been studied using on-line mass spectroscopy [394],... 

In most experimental studies of the influence of organic solvents on enzyme stability, the remaining catalytic activity after exposure to different solvents has been measured. In such a study it was found that the remaining activity of a... 

K. Saimini and E. Kenndler, Influence of Organic Solvents on the Separation Selectivity in Capillary Electrophoresis, J. Chromatog. 792(1-2) 3 (1997). 

Table 15. Influence of organic solvents on activity and stability of alcohol dehydrogenases. Values for the stability are given as the residual activity after 5-h contact with the solvents. The solvents are characterized and classified according to their log P-value [231]. Enzymes are active or stable in the presence of solvents at the mentioned logP value or higher. (Solvents in brackets are those that correspond to the mentioned log P-value.)...

Bielejewska, A., Duszcyk, K., Sybilska,D. (2001) Influence of organic solvent on the behavior of camphor and a-pinene enantiomers in reversed-phase liquid chromatography systems with a-cyclodextrin as chiral additive, J.Chromatog. A 931, 81-93 ... 

V. M. Gun ko, V. V. Turov, J. Skubiszewska-Ziyba, R. Leboda, M. D. Tsapko, and D. Pahjczuk, Structural characteristics of a carbon adsorbent and influence of organic solvents on interfacial water, Appl. Surf. Sci. 214, 178-189 (2003). 

The aqueous mobile phase solutions must frequently contain not only CD but an additional organic solvent whose molecules are also included in the CD cavities(33). The competitive influence of organic solvent on comple-xation equilibria may be expressed by Equation 3 (23) for the apparent CD molar concentration [CD being smaller than the overall molar concentration [CDj° ... 

Silva, C., Matama, T., Guebitz, G.M., and Cavaco-Paulo, A. 2005a. Influence of organic solvents on cutinase stability and accessibility to polyamide flbers. Journal of Polymer Science Part A Polymer Chemistry, 43 2749-53. 

To supplement the data on prolyl isomerization, I will draw on the literature describing rotation about the C-N bond in secondary amides. Early studies in this field were described by Stewart and Siddall in an excellent 1970 review. As we will see, these reactions are related to prolyl isomerization and support the mechanism to be proposed for prolyl isomerization. The mechanism is based on results from a variety of experimental approaches. In all cases, experiments employing kinetic-based probes will be used to obtain an accurate picture of the activated complex in the rate-limiting transition state. The experiments that will be described include thermodynamics, in which activation parameters (i.e., AG, AHt, and ASt) will be described solvent effects, in which the influence of organic solvents and deuterium oxide will be reviewed acid-base catalysis substituent effects and secondary deuterium isotope effects. 

The decrease of the rate constant under the influence of organic solvent was described by the equation [228]... 

Schwer, C. and E. Kenndler, Electrophoresis in fused-sihca capillaries The influence of organic solvent on the electroosmotic velocity and the zeta potential. Anal. Chem. 63 1801-1807 (1991). 

Table 16.2 Influence of organic solvents on the product selectivity of cyclodextrin glycosyltransferase.

Pellegrino et al. (2000) compared 12 different extraction methods for tin speciation concerning the influence of organic solvents, acidity or the presence of complexing agents They found that acidic conditions below 1 mol acidL were necessary to extract all of the investigated compounds. Tropolone improved the extraction of mono- and di-substituted organotins, while... 

The influence of organic solvents on the foaminess is more complex. They control not only the water structure, and by that the protein solubility, but also the protein structure. In spite of this, it is possible to calculate the foaminess as a function of the concentrations of various alcohols by means of the turbidity temperature change, which is corrected by a factor for the direct alcohol/protein interaction [15]. 

S.M. Masselter and A.J. Zemann, Influence of organic solvents in coelectroosmotic capillary electrophoresis of phenols. Anal. Chem., 67,1047-1053,1995. 

Bromme, H.-J., Ziihlke, L., SUber, R.-E., Simm, A., 2008. DCFH2 interactions with hydroxyl radicals and other oxidants influence of organic solvents. Exp. Gerontol. 43, 638-644. 

B. Van der Bruggen, J Geens, C. Van-DECASTEELE, Influence of organic solvents on the performance of polymeric nanofiltration membranes, Sep. Sci. Tech-nol. yj (2002) 783. 

Liu, W. W., X. B. Yan, J. W. Lang, and Q. J. Xue. 2011. Electrochemical behavior of graphene nanosheets in alkylimidazolium tetrafluoroborate ionic liquid electrolytes Influences of organic solvents and the alkyl chains. Journal of Materials Chemistry 21 13205-13212. 

Sarmini, K. Kenndler, E. Influence of organic solvents on the separation selectivity of capillary electrophoresis. J. Chromatogr. A, 1997, 792, 3. 

The proper control of the EOF can be also obtained by adding organic solvents to the electrolyte solution. The influence of organic solvents on the EOF may result from a multiphcity of mechanisms. Organic solvents are expected to influence both the dielectric constant and viscosity of the bulk electrolyte solution. Generally, this leads to the variation of the ratio of the dielectric constant to the viscosity of the electrolyte solution, to which the EOF depends according to Eq. 6. In addition, the local viscosity within the electric double layer can be varied by the adsorption of the organic-solvent molecules in the Stem layer, which... 

---