Zeta potential measurement, aqueous

In another part of this study we wished to see the effects of post-modification treatments on the properties of the modified LDPE surface. Polyethylene samples were photosulfonated for different periods of time. Afterwards they were subjected to an after-treatment by conditioning in an electrolyte solution (aqueous KC1, 10-3 M) for 48 hours and then characterized by zeta potential measurements. This conditioning process resulted in a shift of f to even less negative values (see Fig. 8). This finding may be explained by the swelling of the polymer samples (water adsorption) in water that causes a shift of the shear plane of the electrochemical double layer into the liquid phase. This effect demonstrates that storage conditions and pre-conditioning may exert a pronounced influence on the zeta potential recorded for surface-modified polymers. Phenomena of this kind have already been described in previous literature [26,27],... 

The knowledge of the surface potential for the dispersed systems, such as metal oxide-aqueous electrolyte solution, is based on the model calculations or approximations derived from zeta potential measurements. The direct measurement of this potential with application of field-effect transistor (MOSFET) was proposed by Schenk [108]. These measurements showed that potential is changing far less, then the potential calculated from the Nernst equation with changes of the pH by unit. On the other hand, the pHpzc value obtained for this system, happened to be unexpectedly high for Si02. These experiments ought to be treated cautiously, as the flat structure of the transistor surface differs much from the structure of the surface of dispersed particle. The next problem may be caused by possible contaminants and the surface property changes made by their presence. 

Drug-loaded nanoparticles were also evaluated for their safety and efficacy. Paclitaxel-encapsulated 6-O-CAPRO-p-CD nanospheres and nanocapsules were evaluated for their physical stability in a one-month period in aqueous dispersion form with repeated particle size and zeta potential measurements and AFM imaging to evaluate recrystallization in aqueous medium. Paclitaxel-loaded amphiphilic CD nanoparticles were found to be physically stable for a period of one month whereas recrystallization occurs within minutes when diluted for intravenous (IV) infusion [85], Finally, paclitaxel-loaded amphiphilic nanoparticles were demonstrated to show similar anticancer efficacy against MCF-7 cells when compared to paclitaxel solution in a cremophor vehicle [85],... 

In the literature, the reported use of zeta potential measurement for non-aqueous suspensions is relatively infrequent because non-aqueous suspensions only represent a small percentage of all medicated suspensions. Su and others evaluated the flocculation-deflocculation behavior of cefazolin sodium in non-aqueous media and the effect of surfactants as measured by zeta potential along with sedimentation and porosity measurements. A significant difference in zeta potential was observed when the particles were dispersed in peanut oil and ethyl oleate. The addition of lecithin reduced the zeta potential of cefazolin sodium, resulting in a deflocculated state accompanied by a decrease in sedimentation volume. The effect of surfactant... 

Hashiba, M. et al., The zeta-potential measurement for concentrated aqueous suspension by improved electrophoretic mass transport apparatus—application to AI2O3, ZrOj, and SiC suspensions, J. Mater. Sci., 23, 2893, 1988. 

Nishimura, S. et al., Zeta potential measurement of muscovite mica basal plane-aqueous solution interface by means of plane interface technique, 7. Colloid Interf. Sci., 152, 359, 1992. 

ICP analyses were performed by Plasma Absorption Emission Spectroscopy (ICP-AES). BET surface areas were measured with a Micromeritics TriStar 3000 instrument after degassing the samples at 150 C under a 0.13 Pa vacuum overnight. XPS analyses were performed on a SSI X-probe spectrometer (SSX-100/206 photoelectron spectrometer Fisons) equipped with a monochromatized microfocused Al Ka X-ray source (1486.6 eV) and a hemispherical analyser. The binding energies were calculated relative to the C-(C, H) component of the adventitious Cls carbon peak fixed at 284.8 eV. Zeta potential measurements were carried out in a PENKEM Zeta Meter 500, using 25 mg of sample ultrasonically dispersed in 200 ml of an aqueous solution... 

It has been demonstrated by zeta potential measurements that when powdered human dental enamel is dispersed in the aqueous media that contains salts of the polymeric sulfonates, a substantially negative surface charge is built up on the enamel particles. ... 

Usui, S. and Sasaki, H., Zeta potential measurements of bubbles in aqueous surfactant solutions, J. Colloid Interf Sci, 65, 80 84, 1978. 

The problem of temporal and thermal instability of the U-P[3F-C 12-( 11)] modifier was solved by utilizing a —CF2CF2H (4F) fluorous side chain and increasing the Cl2 mole fraction. Biocidal effectiveness was demonstrated after storage for at least a month under ambient conditions of temperature and humidity. This stability was correlated with zeta potential measurements of accessible near surface charge. These results suggest zeta potential measurements hold promise as a physical method for assessing effectiveness of polycation contact kill and polycation stability in contact with aqueous systems. 

The Pectin-Cisplatin nanoconjugate, a self folding nanoparticulate suspension in aqueous media shows sustained release of the drug. The complex is unaffected by change in pH. The Zeta potential measurement depicts that the polyanionic pectin chains gets shielded when Cisplatin combines to form low affinity bonds. Such conjugation with macromolecular carrier has so far been unreported in the literature for cisplatin delivery. 

ICP analyses were carried out to check the accurate concentration of the An precursor compoimds (Au-pa, Au-pb, Au-pc) in aqueous solution using an Optima 3000XL device (Perkin-Elmer). Optical properties (absorbance) of colloidal solutions were acquired with UV-Vis spectrometer (Avantes-2048). Particle size distribution and zeta potential values were obtained at room temperature from dynamic light scattering and zeta potential measurements, respectively, which were performed on a Malvern Instrument (ZS ZEN 4003). Size analysis (i.e. size, shape, morphology etc.) of colloidal AuNPs was further confirmed with HRTEM (JEM-2 lOOF) at a voltage of 200 kV. 

Electrostatics in Non-Aqueous Media. A popular misconception in studies of non-aqueous dispersions concerns electrostatic effects. Because these are more difficult to measure than in aqueous media, there has been a general tendency to ignore them completely. However, the few investigators who have measured zeta-potentials or electrodeposition with these systems have become convinced of their importance. With the advent of modern commercial instrumentation for zeta-potentials in non-aqueous media it is to hoped that these effects will be measured rather than ignored. 

Table 7.2 Effect of the presence of an anionic polysaccharide on the measured zeta potential (Q of emulsion droplets stabilized by proteins under experimental conditions corresponding to protein-polysaccharide complexation. In all cases the complexes were formed in the bulk aqueous medium before emulsification.

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