Suspension stability increase

Dispersants function through various mechanisms. For water-based systems the preferred mechanism is stabilisation by ionic repulsion. A repulsion force layer is formed around the mineral particle. To maintain the suspension stability, the thickness of this layer around each particle has to be increased with increasing particle size. Layer decay is more frequent with the use of small particles, which results in higher proneness to partial flocculation. Also a uniform layer is necessary for effective stabilisation of all dispersed particles. AMP-95 helps to achieve all these requirements. 

The smallest increases in foam capacity occurred at pH 6.7. Percentages of protein in the soluble fractions varied at this pH. Foam capacity and stability improved and decreased, respectively, at this pH as the salt content of the suspension was increased. The two-step pH adjustment (23) of 6.7 to 4.0 to... 

The use of Kollidon CL-M as a suspension stabilizer has nothing whatever to do with the principle of increasing the viscosity. The addition of 5-9% has practically no effect in changing the viscosity, but strongly reduces the rate of sedimentation and facilitates the redis-persability, in particular, an effect that is consistent with the low viscosity. One of the reasons for this Kollidon CL-M effect is its low (bulk) density, which is only half of that of conventional crospovidone, e.g. Kollidon CL. It can clearly be seen from Fig. 5 that a relative volume of sediment of normal micronized crospovidone of high bulk density (= Crospovidone M) is less and more compact that of Kollidon CL-M, which undergoes hardly any sedimentation. 

The polyoxamers, Lutrol F 68 and Lutrol F 127, in concentrations of 2 - 5 %, expressed in terms of the final weight of the suspension, offer a further opportunity of stabilizing suspensions. They also do not increase the viscosity when used in these amounts and can be combined with all other conventional suspension stabilizers. 

The addition of small amounts of various stabilizers to untreated or polybutadiene-grafted PVC decreased the rate of hydrogen chloride evolution. Thus, as shown in Figure 1, 0.15 phr which is less than 10% of the recommended amounts of a mixture of non-toxic calcium-zinc stabilizers, increased the time for 0.1 mole % dehydrochlorination of suspension polymerized PVC from 28 to 36 minutes and of Type M PVC prepared from the suspension polymer from 41 to 47 minutes. Type P PVC prepared from the same polymer required 49 minutes for the same extent of dehydrochlorination. 

Special interest is devoted to graft copolymers in which the backbone is hydro-phobic and the grafts are hydrophilic (or vice versa). These materials are efficient water suspension stabilizers, and give rise to stable emulsions in water (and even sometimes to microemulsions in the presence of a third constituent). They can be used in many instances whenever oil-in-water or water-in-oil dispersions are needed and the number of applications is steadily increasing. 

Stability of nanoparticles in the reaction mixture in these systems was unprecedented. The unreacted cations appear to stabilize the suspension. Stability of the isolated nanoparticles in water (non-loaded) was also very good (no change in particle size up to three weeks at 4 °C size 226 nm, SD 28.2, n = 7 chemistry used was System 2, Table 1). Substantial swelling then occurs. In saline (0.9 % w/w) the same particles exhibit a rapid increase in size over six hours, from 0.2 nm to... 

Vilchis et al. [81] presented a new idea to achieve better control of the particle size distribution by the synthesis in situ of a water-soluble copolymer of acrylic acid-styrene as suspension stabilizer without additional inorganic phosphate. Publications describe increasing the particle formation by using a physical (population balance, Maxwell fluid, power law viscosity, compartment mixing) modeling approach [22,60,98,105]. 

Chen and Soucie (96) showed that treatment of soy protein isolate with hydro-xylated lecithin lowered the isoelectric point, increased electrophoretic mobility, and signihcantly increased protein dispersibility and suspension stability. Nielsen (97) investigated the interaction of peroxidized phospholipids with several proteins under N2. His findings demonstrated a covalent attachment of phospholipids to proteins whose molecular size is increased. 

The adsorption or incorporation of molecules, such as surfactants and polymers, can create a steric repulsion that prevents aggregation [288-290]. This can also increase suspension stability, important for metered-dose inhaler formulations [291]. Lung surfactant coating on the surface of poly(lactic-co-glycolic) acid microparticles has been shown to dramatically improve dry powder aerosol performance by reducing particle-particle interactions [134,292],... 

Overall, protein suspensions and solutions react similarly to the hydropho-bicity of the solvent. For example, suspensions of ribonuclease, chymotrypsin and lysozyme in nonane, butanol or DMF demonstrated increased structural stability over aqueous conditions (Volkin et al., 1991). The solvents were categorized as non-polar (nonane), polar (butanol) or dipolar (DMF). Thermal stability increased with increasing hydrophobicity and apolarity. Similarly, chymotrypsin activity decreased with decreasing hydrophobicity, consistent with the hypothesis that hydrophilic solvents can more effectively remove bound water than can hydrophobic solvents (Zaks and Klibanov, 1988a). For example, the solubility of water in hydrophobic solvents (Log P < 2.0) was > 0.4 wt %, while the solubility of water in hydrophobic solvents (Log P > 4.0) was < 0.4... 

Figures 7 and 8 show variations in the electric light scattering effect from suspension, stabilized by NaPSS adsorption, with increasing concentration of salts of divalent (Mg2+) and trivalent (Al3+) counterions [18], One observes a steep decrease of the LF effect and some increase of the HF effect at concentration 2.5 X 10 M MgCl2 and 1.6 x 10 5 M A1C13, respectively. These amounts of low molecular salts are sufficient for Na+ to be fully replaced by Mg2+ and Al3+ from the polyion surface. The electro-optical effects vary in a different way when MgCl2 is added to the suspension with no NaPSS adsorbed on the particle surface—Figure 9. This by no means...

The addition of 3.5 X 10 6 M MgCl2 to the suspension, stabilized by MgPSS adsorption, leads to a decrease of the LF effect, while a twofold increase of the HF effect is found as compared to the FIF effect in the absence of salt (Figure 16). The increased conductivity in the presence of MgCl2 can explain the observed reduction of the LF effect but not the increase in the FIF effect. 

Suspension stability is very important since the valve refills after actuation, and, depending on patient use, a varying time can elapse from the can being shaken to the valve being actuated. An informative experiment is to shake the can, leave it for varying periods up to 60 sec and then actuate and collect the dose. With increasing time lapses, the drug may... 

The t -potential and the surface charge of pigment particles in a polymer solution has a direct effect on the suspension stability [194]. Ultra-fine pigment particles (< 0.05 pm) were formed during dispersion, which both adsorb on larger pigment particles and are included in the latex structure. Here, a steric factor increases the sedimentation stability of the suspensions additionally. 

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