Electrostatic charge reduction

Surfactants are incorporated into pMDIs for several reasons. In suspensions, surfactants have been used to stabilize the dispersion by reduction of the electrostatic charge of the micronized drug (19,23). Surfactants may help solubilize the drug... 

The current hypothesis is that layer collapse depends uniquely on the crystal chemistry of Fe2 in the octahedral sheet of the clay or on changes in crystal chemistry that accompany the process of Fe reduction. This hypothesis excludes the possibility that layer collapse occurs in response to an increased electrostatic charge on the clay layer due to the substitution of a divalent for a trivalent ion. Such exclusion is justified on the basis of observations by Mulla (36) that the surface area of smectites depends only on octahedral Fe2, tetrahedral Al, and interlayer K contents. Noticeably absent from this dependence is Mg2, which has the same valence and about the same size as Fe2, but has no apparent influence on surface area. 

Sampling biases can occur from differences in particle size distribution, particle density, particle shape, and particle electrostatic charge. Minimizing these particle property differences will increase the likelihood that the blend content uniformity is a true representation of the batch.13,14 It also aids in the reduction of sampling bias which will improve the experimental blend content uniformity. 

Tissue specimens are fixed in formalin and subsequently embedded in paraffin in the majority of cases. While formalin fixation preserves tissue morphology, it also alters the three-dimensional structure of tissue proteins. This alteration can result in a modification of the antigen s epitopes and/or of its electrostatic charges (EC). The loss of an epitope results in an antigen s inability to react with the paratope of the antibody and can only be corrected by the restoration (retrieval) of the epitope. The reduction of net negative ECs of antigens decreases the avidity of the immune reaction and may be compensated for by prolonging the incubation time with the primary antibody (1) or the use of different antibody diluents (2). 

In most applications more than one particle is observed. As each individual may have its own particle size, methods for data reduction have been introduced. These include the particle-size distribution, a variety of model distributions, and moments (or averages) of the distribution. One should also note that these methods can be extended to other particle attributes. Examples include pore size, porosity, surface area, color, and electrostatic charge distributions, to name but a few. 

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