Ionic strength, mobile-phase effects

The various effects that have been predicted for electrochromatography with perfusive flow may allow for a strong increase of the separation efficiency. The most pronounced effects are expected at high values of to, which can be created by the use of large-pore-sized particles and the use of high-ionic-strength mobile phases. 

Column XTerra MS (pyridine) 3.5 p,m, 15 x 0.46 cm ID. Mobile phase acetonitrile buffer 28-72 (v/v). The calculations of ionic strength ignore the effect of the organic solvent. 

As reported by Zakaria and Brown (Zl), changing the mobile-phase ionic strength has little effect on the retention behavior of nucleosides and bases. The effect of mobile-phase ionic strength is much more pronounced in the case of ribonucleotides, where the compounds are ionized under the mobile-phase conditions. 

Mobile-phase selection for cationic polymers is similar to that for the other polymers in that ionic strength and pH can change the shape of the solute from linear to globular (9). Mobile phases are often low pH e.g., 0.1% trifluo-roacetic acid, including 0.2 M sodium chloride, has been used successfully for polyvinylpyridines. Sodium nitrate can be substituted for the chloride to avoid corrosive effects. Some salt must be included so that ion exclusion does not occur (3). 

Naphthalenedisulfonate-acetonitrile as the only mobile phase with a silica column coated with a crosslinked aminofluorocarbon polymer has proven to be an effective combination for the separation of aliphatic anionic surfactants. Indirect conductivity and photometric detection modes are used to monitor these analytes. The retention of these surfactants is found to depend on both the ionic strength and the organic solvent content of the mobile phase. The mechanism of retention is considered to be a combination of both reverse phase and ion exchange processes. Selective separation of both alkanesulfonates and... 

Intrinsic viscosity measurements were done with a large number of solvents varying in pH, ionic strength, etc., using Cannon-Ubbelohde semimicro dilution viscometers. This was done to provide information on the effect of mobile phase composition on the size of a polymer molecule in solution and thus to facilitate the interpretation of GPC behavior. 

Parameters that should be tested in HPLC method development are flow rate, column temperature, batch and supplier of the column, injection volume, mobile phase composition and buffer pH, and detection wavelength [2], For GC/GLC methods, one should investigate the effects of column temperature, mobile phase flow rate, and column lots or suppliers [38], For capillary electrophoresis, changes in temperature, buffer pH, ionic strength, buffer concentrations, detector wavelength, rinse times, and capillaries lots and supplier should be studied [35, 36], Typical variation such as extraction time, and stability of the analytical solution should be also evaluated [37],... 

Dismer F. Petzold M. Hubbuch J. Effects of ionic strength and mobile phase pH on the binding orientation of lysozyme on different ion-exchange adsorbents. Journal of Chromatography A, 2008, 1194, 11-21. 

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