Ascorbic Acid
C6H8O6 176.12
l-Ascorbic acid
[50-81-7].
(as kore' bik as' id).
+'&img=../../images/v35300/g-55.gif&casNumber=50-81-7&usp=35&nf=30&chemicalStructureImage=true&ID='+parent.myID,600,500);)
C6H8O6 176.12
l-Ascorbic acid
[50-81-7].DEFINITION
Ascorbic Acid contains NLT 99.0% and NMT 100.5% of C6H8O6.
IDENTIFICATION
• B.
A 20-mg/mL solution reduces alkaline cupric tartrate TS slowly at room temperature but more readily upon heating.
ASSAY
• Procedure
Sample:
400 mg of Ascorbic Acid
Titrimetric system
(See Titrimetry 
541
.)
541.)
Mode:
Direct titration
Titrant:
0.1 N iodine VS
Endpoint detection:
Visual
Blank:
100 mL of water and 25 mL of 2 N sulfuric acid. Add 3 mL of starch TS.
Analysis:
Dissolve the Sample in a mixture of 100 mL of water and 25 mL of 2 N sulfuric acid. Add 3 mL of starch TS, and titrate immediately with Titrant until a persistent violet-blue color is obtained.
Calculate the percentage of ascorbic acid (C6H8O6) in the portion of Ascorbic Acid taken:
Result = [(V 
B) × N × F × 100]/W
B) × N × F × 100]/W
| V | = | = sample titrant volume (mL) |
| B | = | = blank titrant volume (mL) |
| N | = | = titrant normality (mEq/mL) |
| F | = | = equivalency factor, 88.06 mg/mEq |
| W | = | = weight of Sample (mg) |
Acceptance criteria:
99.0%–100.5%
IMPURITIES
• Residue on Ignition 281:
NMT 0.1%
281:
NMT 0.1%
SPECIFIC TESTS
• Optical Rotation, Specific Rotation 781S
781S
Sample solution:
100 mg/mL in carbon dioxide-free water. Perform the test immediately after preparation of the Sample solution.
Acceptance criteria:
+20.5
to +21.5
to +21.5
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in tight, light-resistant containers.
• USP Reference Standards 11
11
USP Ascorbic Acid RS 
') + '&img=../../images/v35300/cas-50-81-7.gif',600,500);)
Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
|---|---|---|
| Monograph | Huy T. Dinh, M.S.
Scientific Liaison 1-301-816-8594 |
(DS2010) Monographs - Dietary Supplements |
| Reference Standards | RS Technical Services 1-301-816-8129 rstech@usp.org |
USP35–NF30 Page 2242