Propionic Acid
(proe'' pee on' ik as' id).
DEFINITION
Propionic Acid contains NLT 99.5% and NMT 100.5%, by weight, of propionic acid (C3H6O2).
ASSAY
• Procedure
Sample:
1.5 g of Propionic Acid
Titrimetric system
(See Titrimetry 
541
.)
541.)
Mode:
Direct titration
Titrant:
0.5 N sodium hydroxide VS
Endpoint detection:
Visual
Analysis:
Mix the Sample with 100 mL of recently boiled and cooled water in a 250-mL conical flask. Add phenolphthalein TS to the Sample solution, and titrate with Titrant to the first appearance of a faint pink endpoint that persists for NLT 30 s.
Calculate the percentage of propionic acid (C3H6O2) in the sample taken:
Result = {[(VS 
VB) × N × F]/W} × 100
VB) × N × F]/W} × 100 | VS | = | = volume of Titrant consumed by the sample (mL) |
| VB | = | = volume of Titrant consumed by the blank (mL) |
| N | = | = actual normality of the Titrant (mEq/mL) |
| F | = | = equivalency factor, 74.08 mg/mEq |
| W | = | = weight of the sample (mg) |
Acceptance criteria:
99.5%–100.5% by weight
IMPURITIES
• Limit of Nonvolatile Residue:
Evaporate 20 g of Propionic Acid in a tared dish, and dry at 105
for 1 h: the weight of the residue does not exceed 2.0 mg.
for 1 h: the weight of the residue does not exceed 2.0 mg.
• Heavy Metals 231
231
Test preparation:
To the residue obtained in the test for Limit of Nonvolatile Residue add 8 mL of 0.1 N hydrochloric acid, warm gently until solution is complete, dilute with water to 100 mL, and use 10 mL of the solution.
Acceptance criteria:
NMT 10 ppm
• Limit of Aldehydes
Sample solution:
Transfer 10.0 mL of Propionic Acid to a glass-stoppered 250-mL conical flask containing 50 mL of water and 10.0 mL of sodium bisulfite solution (1 in 80), insert the stopper, and shake vigorously. Allow the mixture to stand for 30 min.
Blank:
Add 50 mL of water and 10.0 mL of sodium bisulfite solution (1 in 80) to a glass-stoppered 250-mL conical flask, insert the stopper, and shake vigorously. Allow the mixture to stand for 30 min.
Titrimetric system
(See Titrimetry 541.)
541.)
Mode:
Residual titration
Titrant:
0.1 N iodine VS
Endpoint detection:
Visual
Analysis:
Titrate the Sample solution and the Blank with Titrant to the same brownish-yellow endpoint.
Acceptance criteria:
The difference between the volume of 0.1 N iodine required for the Blank and that required for the Sample solution is NMT 1.75 mL.
SPECIFIC TESTS
• Distilling Range, Method I 721:
138.5–142.5
721:
138.5–142.5
• Specific Gravity 841:
0.988–0.993
841:
0.988–0.993
• Readily Oxidizable Substances
Sample solution:
Dissolve 15 g of sodium hydroxide in 50 mL of water. Cool, add 6 mL of bromine, stirring to effect complete solution, and dilute with water to 2000 mL. Transfer 25.0 mL of this solution to a glass-stoppered, 250-mL conical flask containing 100 mL of water, and add 10 mL of sodium acetate solution (1 in 5) and 10.0 mL of Propionic Acid. Allow to stand for 15 min, and add 5 mL of potassium iodide solution (1 in 4) and 10 mL of hydrochloric acid.
Blank:
Dissolve 15 g of sodium hydroxide in 50 mL of water. Cool, add 6 mL of bromine, stirring to effect complete solution, and dilute with water to 2000 mL. Transfer 25.0 mL of this solution to a glass-stoppered, 250-mL conical flask containing 100 mL of water, and add 10 mL of sodium acetate solution (1 in 5). Allow to stand for 15 min, and add 5 mL of potassium iodide solution (1 in 4) and 10 mL of hydrochloric acid.
Titrimetric system
(See Titrimetry 541.)
541.)
Mode:
Residual titration
Titrant:
0.1 N sodium thiosulfate VS
Endpoint detection:
Visual
Analysis:
Titrate the Sample solution and the Blank with Titrant just to the disappearance of the brown color.
Acceptance criteria:
The difference between the volume of 0.1 N sodium thiosulfate required for the Blank and that required for the Sample solution is NMT 2.2 mL.
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in tight containers.
Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
|---|---|---|
| Monograph | Robert H. Lafaver, M.S.
Scientific Liaison 1-301-816-8335 |
(EXC2010) Monographs - Excipients |
USP35–NF30 Page 1930