Phosphor dependent variable

Phosphor preparation parameters can be divided into two (2) classes, independent and dependent variables. 

Before we can proceed to an in-depth examination of the dependent variables, we need to examine the steps required to prepare a phosphor. These are shown in 6.5.13., given on the next page. 

The mechanism of U02 " extraction by monoalkyl phosphoric acid reagents appears to be a more complex process than for their dialkyl counterparts. This results from the polymerization of the monoalkyl phosphate in the organic phase and the hydration of the extracted uranyl species so that variable stoichiometries arise for the extractant/water/UO complex. The extraction of from sulfuric acid by mono-2,6,8-trimethylnonyl phosphoric acid (H2DDP) and mono-n-butyl phosphoric acid (H2MBP) as 0.05 M solutions in benzene was shown to follow equations (61) and (62) when an excess of extractant was present. When an excess of uranium was present, equations (63) and (64) applied where n, x, y and z were variable numbers which depended upon the extent of extractant polymerization and hydration of the extracted species. Synergistic effects may also be found with the monoalkyl phosphoric acid extractants and in one recent example the use of tri-n-octylphosphine ocxide (TOPO) as a synergist with H2MEHP allowed the extraction of U02 from phosphoric acid solutions. The uranium may be returned to the aqueous phase by contact with concentrated acid, which reverses the extraction process by protonation of the phosphate. 

It should be noted, however, that the intrinsic properties of a particular chitosan sample depend on structural variables such as the degree of acetylation, the degree of substitution and the average molecular weight. Compared with other amines and polyamines such as polyethylenimine and poly(L-lysine), the primary amino group of the glucosamine unit has an exceptionally low p/Ca value of 6.5, that means that chitosan at pH 7.4 tends to become insoluble because its protonation is low thus, the pH of the transfection medium is important because it affects the transfection efficiency of the chitosan-DNA complexes. In said complexes the N/P ratio (molar ratio of chitosan nitrogen to DNA phosphorous) is also an important parameter. 

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