Retention dependence

Stereochemical analysis can add detail to the mechanistic picture of the Sj l substitution reaction. The ionization mechanism results in foimation of a caibocation intermediate which is planar because of its hybridization. If the caibocation is sufficiently long-lived under the reaction conditions to diffirse away from the leaving group, it becomes symmetrically solvated and gives racemic product. If this condition is not met, the solvation is dissymmetric, and product with net retention or inversion of configuration may be obtained, even though an achiral caibocation is formed. The extent of inversion or retention depends upon the details of the system. Examples of this effect will be discussed in later sections of the chapter. 

In fact, the solute retention depends on the solubihty parameters of the solute, 8 , of the mobile phase, 8 , of the stationary phase, 8, and of the phase ratio given by Equation 4.7 [24] ... 

Weak acids (pK. > 2) Amino acids. Carboxylic acids 6 - 7.4 Solutes ionized retention dependent upon the nature of the ion pair. 

Ionization of solutes is suppressed retention dependent upon the nature of solute (not ion pair). 

The retention depends on the nature of both the stationary phase and the organic modifier in the mobile phase. Therefore CHI values obtained using different systems show different sensitivities towards solute characteristics. This has been studied systematically and used for the quantitative calculation of solute molecular descriptors (H-bond donor capacity, H-bond acceptor capacity and dipolarity/polarizability) for application in a general solvation equation [21]. 

Retention depended on treatment variables. 2Retention varied among cultivars. 

A typical module showing the input stream vectors xijy output stream vectors yik, specified equipment parameter vector pf, unspecified equipment parameter vector qt, and the retention (dependent) variable vector r-. 

Lovelace et al. (20) noted that the effect of oxalic acid on calcium retention depended on the age of the animal (Figure 4). The two experimental diets contained cod liver oil and 0.3% calcium. Milk was the main source of calcium, and to one diet was added 60 mg of potassium oxalate daily. Ten-day balances were determined throughout the study until rats were 175 days of age. At 50 days of age, rats fed oxalate retained about 25% of the calcium,... 

Obviously, the magnitude of the temperature effect on retention depends on the difference in the enthalpy of the solute in either phase, and is specific for each solute. Therefore, it also changes the column selectivity. There is no retention and no temperature effect for AH=0. 

Size exclusion is the simplest form of chromatography, in which retention depends only on the permeation of analyte into and out of the pore system of the stationary phase. In contrast to other modes of chromatography, such as reversed phase or... 

For long-term heat ageing, property retention depends on the property and grades considered, notably the heat stabilizers used. For a heat-sensitive characteristic such as elongation at break, the values for a given polyethylene after ageing at 120°C are roughly ... 

For long-term heat ageing, property retention depends on the property and grades considered, notably the heat stabilizers used. 

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