Mobile phase properties

Mobile Phase Paraneter Influence on Mobile Phase Properties Effect on Sai >le Retention... 

Mass spectra influenced by mobile-phase properties... 

In liquid-solid and liquid-liquid systems, manipulation of mobile phase properties is the dominant approach. Mixtures of poor and good solvents for the types of molecules being separated are prepared and retention observed. There are fewer stationary phases for liquid mobile phase systems for this reason and at least one other. 

Mobile-phase parameter Influence on mobile-phase properties Effect on sample retention... 

Since CEC is a hybrid technique, the differential migration of analytes through the stationary phase bed will generally involve lipophilic, electrostatic, and electrophoretic processes between the analytes and the stationary and mobile phases. Consequently, the applied voltage and electrical field strength and the mobile phase properties such as pH, buffer concentration, ionic strength, temperature, and the organic content will all affect the separation. For a detailed discussion, also refer to reference 10. 

Impact of the Organic Solvent and Other Mobile-Phase Properties on Peptide Separation in Reversed-Phase Chromatography... 

Benincasa et al. (2003) also studied the effect of ionic strength and electrolyte composition on hydrodynamic characteristics of HS. The author s reported that components of different HS fractions behave like organic acids, but that the retention level of fractions with larger components may not be accurately modulated by varying mobile phase properties as these species are either totally retained in acidic phases or released before the void peak at pH 4.2. Authors concluded that pronounced differences exist in the physicochemical properties of some HS components even when particle sizes were similar. 

Many reviews have been written on the preparation, physico-chemical properties and application of silica in modem separation science [5-7]. RP LC with silica based bonded stationary phases is utilised for the majority of LC separations in laboratories world-wide. Their ubiquity derives from their versatility, in that generally a wide range of both ionic and non-ionic analyte species can be separated with these columns by careful selection of the stationary phase and mobile phase properties. 

Mobile Phase Properties. Some chemicals that could be used in SFC are listed in Table 2. The one that has been used most commonly is carbon dioxide, and it will be the focus of this short introduction. Figure 11.1 shows the pressure-volume phase diagram for CO2 at various temperatures. The critical values (Pc = 7.4 MPa, Vc = 96 mL, and Tc = 31° C) intersect approximately at the point marked X. Liquid exists in the lined space at the left of the diagram, gas and liquid are in equilibrium in the space cut off by the dashed line, supercritical fluid exists above the critical temperature, and gas exists at the right. Remember that the critical temperature is that temperature above which a gas cannot be liquefied no matter how high the pressure. 

The dependence of EOF mobility, pE0F, on mobile-phase properties has been explored theoretically, and confirmed in a number of experiments on silica and bonded silica columns [49]. Comparisons have also been made with the results... 

The evaporative light scattering detector (ELSD) [47] is based on the ability of fine particulate matter of a solute to scatter light. To obtain suitable analyte particles, the column effluent is nebulized by an inert gas in the nebulizer and aerosol droplets are allowed to evaporate in the drift tube. Droplet size is related to mobile phase properties (surface tension, density, and viscosity). Usually, high solvent-to-gas flow ratio provides the best sensitivity because it produces the largest droplet diameters. 

Whether a detector linked to an HPLC system is suitable is determined by the properties of compounds. If the compound does not absorb UV-Visible and non-fluorescent light, other properties should be chosen in combination with mobile-phase properties, such as refractive index... 

Organic Solvent and Other Mobile Phase Properties... 

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