Silicon dioxide suspensions

Chemical/Physical. Endosulfan detected in Little Miami River, OH was readily hydrolyzed and tentatively identified as endosulfan diol (Eichelberger and Lichtenberg, 1971). Undergoes slow hydrolysis forming the endosulfan diol and sulfur dioxide (Worthing and Hance, 1991). The hydrolysis half-lives at pH values (temperature) of 3.32 (87.0 °C), 6.89 (68.0 °C), and 8.69 (38.0 °C) were calculated to be 2.7, 0.07, and 0.04 d, respectively (Ellington et al., 1988). Greve and Wit (1971) reported hydrolysis half-lives of P-endosulfan at 20 °C and pH values of 7 and 5.5 were 37 and 187 d, respectively. In a 1 pM sodium bicarbonate buffer solution at pH 8.15 and 28 °C, suspensions of sea sand, titanium dioxide, a-ferric oxide, a-FeOOH, laponite, and silicon dioxide catalyzed the hydrolysis of a-endosulfan to endosulfan diol. The uncatalyzed hydrolysis rate constant and half-life was 4.01 x lO Vsec and 0.20 d, respectively (Walse et al., 2002). 

Each 5 mL of VANTIN oral suspension contains cefpodoxime proxetil equivalent to 50 mg or 100 mg of cefpodoxime activity after constitution and the following inactive ingredients artificial flavorings, butylated hydroxy anisole, carboxymethylcellulose sodium, microcrystalline cellulose, carrageenan, citric acid, colloidal silicon dioxide, croscarmellose sodium, hydroxypropylcellulose, lactose, maltodextrin, natural flavorings, propylene glycol... 

Add, in small quantities, the remaining half of magaldrate cake or powder and disperse well. Mix for 1 hour and then remove heat. (Adjust the speed of the agitator and of the homogenizer to maintain the mobility of suspension.) Separately blend silicon dioxide colloidal with xanthan gum and disperse the blend in glycerin, with constant mixing. 

Carafate suspension for oral administration contains 1 g sucralfate per 10 mL. Carafate suspension also contains colloidal silicon dioxide, FD C red no. 40, flavor, glycerin, methylcellulose, methylparaben, microcrystal-... 

Silicified microcrystalline cellulose is manufactured by codrying a suspension of microcrystalline cellulose particles and colloidal silicon dioxide so that the dried finished product contains 2% w/w colloidal silicon dioxide. 

In aerosols, other than those for inhalation, colloidal silicon dioxide is used to promote particulate suspension, eliminate hard settling, and minimize the clogging of spray nozzles. Colloidal silicon dioxide is also used as a tablet disintegrant and as an adsorbent dispersing agent for liquids in powders. Colloidal silicon dioxide is frequently added to suppository formulations containing lipophilic excipients to increase... 

Tukker JJ, De Blaey CJ. The addition of colloidal silicon dioxide to suspension suppositories II. The impact on in vitro release and bioavailability. Acta Pharm Technol 1984 30 I55-I60. 

Silica T40, a pure silicon dioxide of particle size 5-30 nm, was used as the solid support. Approximately 0.2 g of support was weighed into a 20 ml vial, 8 ml of acetone was added, and the suspension was sonicated for 1-1.5 h in an ultrasonic bath. During this time, the vial was taken out of the ultrasonic bath four or five times and the suspension was decanted into a new vial to remove the particles that had conglomerated on the wall of the vial above the suspension. Then 0.8 g of Alltech CS-10 was added, and the suspension was further sonicated for ca. 30 min. After standing, the suspension was stable for some days. 

Estel, K., et al., 2010. Influence of ionic strength and pH-value on the silicon dioxide polishing behaviour of slurries based on pure silica suspensions. MRS Proc. 1249, 97—102. 

Silica (silicon dioxide) in the form of a colloidal, basic suspension is an abrasive that is used effectively for final polishing in a broad range of applications. 

The inclusion of nucleation inhibitors such as silicon dioxide can modulate nu-cleation process, thus prolonging the suspension stability. Particle size control of amorphous formulations is essential for homogeneity and withdrawability for dosing accuracy. 

Diflucan for oral suspension contains 350 or 1400 mg of fluconazole and the following inactive ingredients sucrose, sodium citrate dihydrate, citric acid anhydrous, sodium benzoate, titanium dioxide, colloidal silicon diox-... 

We have used a rat traeheal explant system to examine the role of AOS in particle uptake. When traeheal explants are briefly immersed in a suspension of a mineral dust, dust partieles adhere to the epithelial cell surfaces if the explants are then maintained in organ eulture in air, the epithelial cells slowly take up particles from the apical surface (see Fig. 1). The relative basal level of uptake of different types of particles is quite different (see Table 3), but every type of mineral particle thus far examined (asbestos, carbon, titanium dioxide, iron oxide, talc, wollastonite, or silicon carbide) enters the epithelial cells (3,4,51-54). This system offers several simplifying advantages for studying particle uptake, ineluding lack of airspace inflammatory cells, maintenance of normal levels of intraeel-lular antioxidant defense (Churg A, unpublished data), and retention of a polarized cell structure with normal apical differentiation. 

Uptake ean similarly be increased by exogenous sources of AOS. Brief exposure to whole cigarette smoke, which is a highly concentrated source of AOS and other radicals, and then to a mineral dust suspension produces considerably greater uptake of asbestos, titanium dioxide, fibrous silicon carbide, and talc (51 -53 Fig. 2). The increase in uptake is proportional to the dose of cigarette smoke, and the smoke effect can be inhibited by catalase, superoxide dismutase (which destroys superoxide anion), or deferoxamine (see Fig. 2). The effects of low levels of ozone are similar (Fig. 3), but differ from cigarette smoke in that superoxide dismutase is not protective (126). Smoke also fails to enhance the uptake of nonfibrous silicon carbide or iron oxide (hematite 53) the latter observation is particnlarly interesting because it was recently shown (127) that hematite does not catalyze the formation of AOS. This observation emphasizes the idea that redox-active surface iron, as opposed to compositional iron, is cracial to AOS formation and particle nptake. 

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