Colloidal Silicon Dioxide
SiO2 60.08

Silica [7631-86-9].
» Colloidal Silicon Dioxide is a submicroscopic fumed silica prepared by the vapor-phase hydrolysis of a silicon compound. When ignited at 1000 for 2 hours, it contains not less than 99.0 percent and not more than 100.5 percent of SiO2.
Packaging and storage— Preserve in well-closed containers.
A: Transfer about 5 mg to a platinum crucible, and mix with about 200 mg of anhydrous potassium carbonate. Ignite at a red heat over a burner for about 10 minutes, and cool. Dissolve the melt in 2 mL of freshly distilled water, warming if necessary, and slowly add 2 mL of ammonium molybdate TS to the solution: a deep yellow color is produced.
B: [Caution—Avoid contact with o-tolidine when performing this test, and conduct the test in a well-ventilated hood. ] Place 1 drop of the yellow silicomolybdate solution obtained in Identification test A on a filter paper, and evaporate the solvent. Add 1 drop of a saturated solution of o-tolidine in glacial acetic acid to reduce the silicomolybdate to molybdenum blue, and place the paper over ammonium hydroxide: a greenish blue spot is produced.
pH 791: between 3.5 and 5.5, in a 1 in 25 dispersion.
Loss on drying 731 Dry it in a tared platinum crucible at 105 for 2 hours: it loses not more than 2.5% of its weight. Retain the dried specimen, in the crucible, for the test for Loss on ignition.
Loss on ignition 733 Ignite the portion of Colloidal Silicon Dioxide, retained from the test for Loss on drying, at 1000 ± 25 to constant weight: the previously dried Colloidal Silicon Dioxide loses not more than 2.0% of its weight.
Arsenic, Method I 211 Prepare the Test Preparation as follows. Transfer 2.5 g to a flask, add 50 mL of 3 N hydrochloric acid, and reflux for 30 minutes using a water condenser. Cool, filter with the aid of suction, and transfer the filtrate to a 100-mL volumetric flask. Wash the filter and flask with several portions of hot water, and add the washings to the flask. Cool, dilute with water to volume, and mix: a 15.0-mL portion of this solution, to which 3 mL of hydrochloric acid has been added, meets the requirements of the test, the addition of the 7 N sulfuric acid being omitted. The limit is 8 µg per g.
Assay— Transfer about 500 mg of Colloidal Silicon Dioxide to a tared platinum crucible, ignite at 1000 ± 25 for 2 hours, cool in a desiccator, and weigh. Add 3 drops of sulfuric acid, and add enough alcohol to just moisten the sample completely. Add 15 mL of hydrofluoric acid, and in a well-ventilated hood evaporate on a hot plate to dryness, using medium heat (95 to 105) and taking care that the sample does not spatter as dryness is approached. Heat the crucible to a red color with the aid of a Bunsen burner. Ignite the residue at 1000 ± 25 for 30 minutes, cool in a desiccator, and weigh. If a residue remains, repeat the procedure, beginning with “add 15 mL of hydrofluoric acid.” The weight lost by the assay specimen, previously ignited at 1000 ± 25, represents the weight of SiO2 in the portion taken.
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Topic/Question Contact Expert Committee
Monograph Kevin T. Moore, Ph.D.
(EM105) Excipient Monographs 1
USP32–NF27 Page 1338
Pharmacopeial Forum: Volume No. 31(4) Page 1232
Chromatographic Column—
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.