Citric acid monohydrate is an organic acid. It may be used in the preparation of tris-citrate buffer and Otto I isolation buffer used in bioprotocols. It may also be used to improve the release of diltiazem hydrochloride from melt extruded matrix tablets.

• CAS Number: 5949-29-1
• Linear Formula: HOC(COOH)(CH2COOH)2 · H2O
• Molecular Weight: 210.14
• Beilstein Registry Number: 4018641
• EC Number: 201-069-1
• MDL Number: MFCD00149972
• PubChem Substance ID: 57648756
• Grade: ACS reagent, reag. ISO, reag. Ph. Eur.
• InChI Ke: YASYEJJMZJALEJ-UHFFFAOYSA-N
• Grade: Puriss. p.a.
• Assay: 99.5-100.5% (calc. on anhydrous substance), 99.5-102%
• Impurities: =0.005% insolubles in water, =2 ppm heavy metals (as Pb), 7.5-9.0% water (Karl Fischer)
• Ign. Residue: =0.01% (as SO4)
• pKa: (1) 3.13, (2) 4.76, (3) 6.4
• Anion Traces: Chloride (Cl-): =5 mg/kg, Oxalate (C2O42-): =50 ppm, Phosphate (PO43-): =10 mg/kg, Sulfate (SO42-): =20 ppm
• Cation Traces: Ca: =50 mg/kg, Cu: =5 mg/kg, Fe: =3 ppm, Pb: =2 ppm, Zn: =5 mg/kg
• Suitability: Complies for appearance of solution, Complies for reaction against H2SO4