National Drug Standard Code CDE Filing Number A for Active Pharmaceutical Ingredient of Pharmaceutical Grade Guaifenesin for Formulation

Pharmaceutical grade guaifenesin, as an expectorant active pharmaceutical ingredient, has its quality standards strictly regulated in pharmacopoeias, covering key aspects such as description, identification, tests, and assay to ensure medicinal safety and efficacy.

1. Description

This product is a white crystalline powder; odorless or with a slight characteristic odor. It is readily soluble in water and soluble in ethanol or propylene glycol. The melting point is 78–82°C, decomposing simultaneously upon melting, requiring precise temperature control using a melting point apparatus.

2. Identification

- Chemical identification: Dissolve about 0.1 g of the substance in 5 ml of sodium hydroxide test solution, heat to boiling, producing the characteristic odor of guaiacol (similar to the pungent smell of phenols); after cooling, acidify to yield a white precipitate.

- Infrared spectroscopy: The infrared absorption spectrum should be consistent with the reference spectrum (Spectrum Set 1035), confirming the structure through characteristic peaks (e.g., absorption peaks for hydroxyl and ether groups).

3. Tests

- Acidity: Dissolve 1.0 g in 20 ml of water; the pH should be 5.0–7.0 (determined using a precision pH meter).

- Chlorides: Compare 0.5 g of the substance, tested as directed (General Chapter 0801), with a reference solution prepared from 5.0 ml of standard sodium chloride solution; not more intense (0.01%).

- Salts: Compare 1.0 g of the substance, tested as directed (General Chapter 0802), with a reference solution prepared from 1.0 ml of standard potassium solution; not more intense (0.01%).

- Related substances: Using high-performance liquid chromatography (General Chapter 0512) with octadecylsilane-bonded silica gel as the filler and methanol-water (40:60) as the mobile phase, detect at 274 nm. If impurity peaks are present in the test solution, no single impurity peak area should exceed 0.5 times that of the main peak in the reference solution (0.5%), and the sum of all impurity peak areas should not exceed the main peak area of the reference solution (1.0%).

- Loss on drying: When dried at 80°C to constant weight, the loss should not exceed 0.5% (General Chapter 0831).

- Residue on ignition: Not more than 0.1% (General Chapter 0841).

- Heavy metals: Dissolve 1.0 g in 2 ml of acetate buffer (pH 3.5) and sufficient water to make 25 ml, tested as directed (General Chapter 0821, Method I); not more than 10 ppm.

4. Assay

Using ultraviolet-visible spectrophotometry (General Chapter 0401). Accurately weigh about 0.1 g, place in a 100 ml volumetric flask, dissolve and dilute to volume with 0.1 mol/L solution, mix well; accurately transfer 5 ml to another 100 ml volumetric flask, dilute to volume with 0.1 mol/L solution, mix well. Measure the absorbance at 274 nm, calculate using the absorption coefficient () of 153 for C10H14O4. Calculated on the dried basis, the content of C10H14O4 should be 98.0%–102.0%.

National Drug Standard Code CDE Filing Number A for Active Pharmaceutical Ingredient of Pharmaceutical Grade Guaifenesin for Formulation

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