Phase parameters affecting

The effect of the mobile-phase composition on the operation of the different interfaces is an important consideration which will be discussed in the appropriate chapter of this book but mobile-phase parameters which affect the operation of the interface include its boiling point, surface tension and conductivity. The importance of degassing solvents to prevent the formation of bubbles within the LC-MS interface must be stressed. 

CA Dunbar, AJ Hickey. Selected parameters affecting characterization of nebulized aqueous solutions by inertial impaction and comparison with phase-doppler analysis. Eur J Pharm Biopharm 48 171-177, 1999. 

In the individual compartments quasi-steady state is achieved depending on emissions, degradation rates and spatial distribution of DDT. According to the seasonality of the parameters affecting degradation rates, e.g. temperature and oxidant abundance, the compartmental burdens in steady state follow a seasonal cycle. As the sources and consequently most of the DDT mass is located in the northern hemisphere, the cycle is defined by the climate of that hemisphere. Times needed to to achieve quasi staty state in the compartments are equal in the AGG and SAT experiment, as well as amplitude and phase of the burden time series. Vegetation reaches quasi-steady state within 2-4 years, and atmosphere already within 2 years. These... 

Capillary electrochromatography (CEC) is a miniaturized separation technique that combines aspects of both interactive chromatography and capillary electrophoresis. In this chapter, the theory of CEC and the factors affecting separation such as the stationary phase and mobile phase parameters have been discussed. The chapter focuses on the types and preparation of columns for CEC and describes the progress made in the development of open-tubular, particle-packed, and monolithic columns. The detection techniques in CEC such as the traditional UV detection and improvements made in coupling with more sensitive detectors such as mass spectrometry are also described. The chapter provides a summary of some applications of CEC in the analysis of pharmaceuticals and biotechnology products. 

Similar to HPLC and CE there are a number of important variables that affect the separation process in CEC. These include the electric field strength, mobile phase parameters, and stationary phase surface chemistry that are described as follows. 

It has been shown (, , 2.) that a membrane casting dope is a strongly structurlzed polymer solution, and that the morphology of the membrane surface layer can be correlated to the structure of the casting solution. The latter parameter affects the nature and details of the phase inversion process occuring in the upper part of the cast solution, in an incipient skin. Thus the solution structure is one of the factors responsible for the skin properties, and consequently for the performance of the ultimately formed asymmetric membrane. 

Accordingly, two major parameters affect the band profiles in nonlinear chromatography the column efficiency, and the amount of sample injected or loading factor. Parameter F (phase ratio) depends on the total porosity of the packing and cannot be changed in practice. 

However, other parameters, such as the salt concentration, ionic strength, and especially the natures of anions in the reacting solution, play essential roles in determining the properties of the precipitated solids. The effects of anions are related to their tendency to be incorporated in the solute complexes formed on aging, which in turn differ with each cation. These anion-containing solutes often act as precursors to the solid-phase formation, affecting the properties of the final products. Various phenomena are illustrated and discussed in the text that follows. 

For purification, scale-up considerations are important even in the earliest phases of development. It is important to avoid the use of purification techniques of limited scale-up potential even for early clinical production because thorough justification of process changes and demonstration of biochemical comparability are necessary prior to product licensure. For successful scale-up, it is important to understand the critical parameters affecting the performance of each purification step at each scale. Conversely, it is important to verify that the scaled-down process is an accurate representation of the scaled-up process, so that process validation studies, such as viral clearance and column lifetime studies, can be performed at the laboratory scale. 

Many parameters affect the mass transfer between two phases. As we discussed above, the concentration gradient between the two phases is the driving force for the transfer and this, together with the over-all mass transfer coefficient, determines the mass transfer rate. The influence of process parameters (e. g. flow rates, energy input) and physical parameters (e. g. density, viscosity, surface tension) as well as reactor geometry are summed up in the mass transfer coefficient. The important parameters for Kta in stirred tank reactors are ... 

The coagulation rate depends upon physical parameters (temperature, velocity gradient, number and dimension of colloid), determining the collision frequency and upon chemical parameters (pH, Al(III) dosage, surface concentration of dispersed phase S), affecting the collision efficiency factor a... 

Wilson et al., 1986). The source of detritus will clearly affect the period of refractory decay. For example, the refractory phase of phytodetritus may last for only a few weeks compared to vascular plant detritus which may last for months to years (Valiela, 1995 Opsahl and Benner, 1999). Finally, temperature and size of the decomposing detrital particles also represent parameters affecting decay rate. Early work by Hodson et al. (1983) showed that lignocellulose remineralization rates were enhanced with decreasing particle size due to the higher relative abundance of microbes with an increasing surface-to-volume ratio. To no surprise, litter bag experiments indicate that increases in temperature also increase decay rates due to enhanced microbial activity (Wilson et al., 1986). 

In the second place, the parameters listed in table 4.2 cannot always be varied independently and, moreover, will have side effects on yet other parameters. All the capacity parameters affect the phase ratio (V/ V. If all other parameters are kept constant, then the film thickness and the surface area will affect Ks, the porosity will affect Vm and the diameter of open columns will affect both Vm and Vs. However, it is often impossible to keep all other parameters constant. For instance, it would be very difficult to vary the porosity without changing the surface area. An example of the effect of variations in the capacity parameters on other parameters is the decrease in the number of theoretical plates in the column that usually accompanies an increase in the stationary phase film thickness in GLC. 

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