Epitochem

Citric Acid Monohydrate / Anhydrous

Citric Acid Monohydrate / Anhydrous

Citric acid is a naturally occurring organic acid found in citrus fruits. It appears as a white or colorless crystalline powder with a strong acidic taste. The monohydrate form contains one molecule of water and is slightly hygroscopic, whereas the anhydrous form is free from water and remains more stable in dry conditions. Citric acid is highly soluble in water and freely soluble in ethanol. It functions as an acidifying, buffering, and chelating agent in pharmaceutical formulations, food products, and cosmetics.

Chemical Name and CAS Registry Number

  • Citric Acid Monohydrate: 2-Hydroxy-1,2,3-propane-tricarboxylic acid monohydrate [5949-29-1]

  • Citric Acid Anhydrous: 2-Hydroxy-1,2,3-propane-tricarboxylic acid [77-92-9]

Functional Category :-Acidifying agent; buffering agent; chelating agent; flavor enhancer.

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Pharmacopeial Specifications

Test PhEur USP-NF JP
Identification ✓ ✓ ✓
Appearance ✓ — ✓
pH (5% w/v solution) 2.2–2.5 1.8–2.4 1.8–2.5
Water Content 7.5–9.0% (Monohydrate) ≤0.5% (Anhydrous) ≤0.5% (Anhydrous)
Heavy Metals ≤10 ppm ≤10 ppm ≤10 ppm
Assay 99.5–100.5% 99.5–100.5% 99.5–100.5%

Applications in Pharmaceutical Formulation or Technology

Citric acid is widely used in pharmaceutical formulations as an acidifying and buffering agent in oral, topical, and parenteral preparations. It enhances solubility and stability of active ingredients, acts as a chelating agent in metal-sensitive formulations, and improves palatability in syrups and effervescent tablets. Additionally, it is used in combination with bicarbonates for effervescent drug delivery systems.

Comments

Citric acid is naturally occurring and widely used in pharmaceutical, food, and cosmetic applications. The monohydrate form is more commonly used in aqueous formulations, while the anhydrous form is preferred for effervescent and dry formulations due to its low moisture content. It is generally recognized as safe (GRAS) and approved for use in multiple regulatory jurisdictions.

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