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Summary of Silicon Dioxide as a Pharmaceutical Excipient in the Fourth Supplement of the Pharmacopoeia 2020 Edition
Take 1g of this product, weigh it accurately, place it in a platinum crucible that has been ignited to constant weight at 1000℃, ignite at 1000℃ for 1 hour, take it out, cool, and weigh accurately.
This document specifies in detail the standards for silicon dioxide as a pharmaceutical excipient in the Fourth Supplement of the Pharmacopoeia 2020 Edition, covering basic information, properties, identification, inspection, content determination, category, storage and other aspects. The specific content is as follows:
1.1 Basic Information
- Name and Chemical Formula: Chinese name is Silicon Dioxide, English name is Silicon Dioxide, chemical formula is SiO₂－χH₂O, and CAS number is [14464-46-1].
- Preparation Method: Sodium silicate reacts with acids (such as hydrochloric acid, sulfuric acid, phosphoric acid, etc.) or salts (such as ammonium chloride, ammonium sulfate, ammonium bicarbonate, etc.) to form silicic acid precipitate (hydrated silicon dioxide), which is then washed with water to remove impurities and dried.
- Content Requirement: Calculated based on the ignited product, the content of silicon dioxide (SiO₂) shall not be less than 99.0%.
1.2 Properties
This product is a white loose powder, soluble in hot sodium hydroxide test solution, and insoluble in water or dilute hydrochloric acid.
1.3 Identification Method
Take about 5mg of this product, place it in a platinum crucible, add 200mg of potassium carbonate, mix well, and ignite at 600～700℃ for 10 minutes. After cooling, add 2ml of water, heat slightly to dissolve, then slowly add 2ml of ammonium molybdate test solution (preparation method: take 6.5g of molybdic acid, add 14ml of water and 14.5ml of concentrated ammonia solution, shake to dissolve; after cooling, slowly add the cooled mixture of 32ml of nitric acid and 40ml of water while stirring; let stand for 48 hours, filter, and take the filtrate). The solution shall show a dark yellow color.
1.4 Inspection Items and Standards
| Inspection Item | Inspection Method | Qualification Standard |
| Particle Size | Take 10g of this product and inspect according to Determination of Particle Size and Particle Size Distribution (General Chapter 0982, Method 2 (1)). | The amount of the test sample passing through a No.7 sieve (125μm) shall not be less than 85%. |
| Acidity and Alkalinity | Take 1g of this product, add 20ml of water, shake, filter, and determine the pH value of the subsequent filtrate according to Determination of pH Value (General Chapter 0631). | The pH value shall be in the range of 5.0～7.5. |
| Chloride | Take 0.5g of this product, add 50ml of water, reflux for 2 hours under heating, cool, make up the volume to 50ml, shake well, filter; take 10ml of the subsequent filtrate, inspect according to Determination of Chloride (General Chapter 0801), and compare with the reference solution prepared with 10.0ml of standard sodium chloride solution. | Shall not be more concentrated than the reference solution (equivalent to containing 0.1% chloride). |
| Sulfate | Take 10ml of the subsequent filtrate from the chloride inspection, inspect according to Determination of Sulfate (General Chapter 0802), and compare with the reference solution prepared with 5.0ml of standard potassium sulfate solution. | Shall not be more concentrated than the reference solution (equivalent to containing 0.5% sulfate). |
| Loss on Drying | Dry this product at 145℃ for 2 hours and determine the weight loss. | The weight loss shall not exceed 5.0% (General Chapter 0831). |
| Loss on Ignition | Take 1.0g of the residue from the loss on drying, weigh it accurately, ignite at 1000℃ for 1 hour, and determine the weight loss. | The weight loss shall not exceed 8.5% of the weight of the dried product. |
| Iron Salt | Take 0.2g of this product, add 25ml of water, 2ml of hydrochloric acid and 5 drops of nitric acid, boil for 5 minutes, cool, filter; wash the filter and combine the filtrate and washing liquid, add 50mg of ammonium persulfate, dilute with water to 35ml, inspect according to Determination of Iron Salt (General Chapter 0807), and compare with the reference solution prepared with 3.0ml of standard iron solution. | Shall not be darker than the reference solution (equivalent to containing 0.015% iron salt). |
| Heavy Metals | Take 3.3g of this product, add 40ml of water and 5ml of hydrochloric acid, heat and boil slowly for 15 minutes, cool, filter; place the filtrate in a 100ml volumetric flask, wash the filter and add the washing liquid to the volumetric flask, dilute with water to the marked volume, shake well; take 20ml of this solution, add 1 drop of phenolphthalein indicator, add ammonia test solution until light red color appears, add 2ml of acetate buffer solution (pH3.5), and add water to 25ml; inspect according to Determination of Heavy Metals (General Chapter 0821, Method 1). | The content of heavy metals shall not exceed 30 parts per million. |
| Arsenic Salt | Take 20ml of the solution from the heavy metals inspection, add 5ml of hydrochloric acid, and inspect according to Determination of Arsenic Salt (General Chapter 0822, Method 1). | Shall comply with the regulations (equivalent to containing 0.0003% arsenic salt). |
1.5 Content Determination
Take 1g of this product, weigh it accurately, place it in a platinum crucible that has been ignited to constant weight at 1000℃, ignite at 1000℃ for 1 hour, take it out, cool, and weigh accurately. Moisten the residue with water, add 10ml of hydrofluoric acid dropwise, and evaporate to dryness in a water bath; after cooling, continue to add 10ml of hydrofluoric acid and 0.5ml of sulfuric acid, evaporate to nearly dry in a water bath, transfer to an electric furnace, heat slowly until the acid vapor is completely removed, then ignite at 1000℃ to constant weight, cool, and weigh accurately. The weight loss between the two weighings is the weight of silicon dioxide (SiO₂) in the test sample.
1.6 Category and Storage
- Category: Pharmaceutical excipient, mainly used as a glidant, suspending agent, etc.
- Storage: Shall be stored in a sealed container to ensure stable quality.
(Note: Part of the content in this document may be AI-generated)
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