Ascorbic Acid Tablets
DEFINITION
Ascorbic Acid Tablets contain NLT 90.0% and NMT 110.0% of the labeled amount of ascorbic acid (C6H8O6).
IDENTIFICATION
•  A.
Sample solution:  Triturate a quantity of finely powdered Tablets with diluted alcohol to make a solution of ascorbic acid with a concentration of 20 mg/mL, and filter.
Analysis:  Add alkaline cupric tartrate TS to a portion of the Sample solution.
Acceptance criteria:  The Sample solution reduces alkaline cupric tartrate TS slowly at room temperature but more readily upon heating.
•  B.
Sample solution:  Use the Sample solution from Identification test A.
Analysis:  To 2 mL of the Sample solution add 4 drops of methylene blue TS, and warm to 40.
Acceptance criteria:  The deep blue color of methylene blue becomes appreciably lighter or is completely discharged within 3 min.
•  C.
Sample solution:  Use the Sample solution from Identification test A.
Analysis:  To 1 mL of the Sample solution add 15 mL of trichloroacetic acid solution (1 in 20) and 200 mg of activated charcoal, shake the mixture vigorously for 1 min, and pass through a small fluted filter, returning the filtrate if necessary, until clear. To 5 mL of the filtrate add 1 drop of pyrrole, agitate gently until dissolved, and then heat in a bath at 50.
Acceptance criteria:  A blue color develops.
ASSAY
•  Procedure
Sample stock solution:  Transfer NLT 20 Tablets to a 1000-mL volumetric flask containing 250 mL of metaphosphoric–acetic acids TS. Insert the stopper in the flask, and shake by mechanical means for 30 min or until the tablets have disintegrated completely. Dilute with water to volume.
Sample solution:  Transfer a portion of the Sample stock solution to a centrifuge tube, and centrifuge until a clear supernatant is obtained. Quantitatively dilute the clear supernatant with water, if necessary, to obtain a solution containing 0.5 mg/mL of ascorbic acid.
Blank:  A mixture of 5.5 mL of metaphosphoric–acetic acids TS and 15 mL of water
Titrimetric system 
Mode:  Direct titration
Titrant:  Standard dichlorophenol–indophenol VS
Endpoint detection:  Visual, a rose-pink color that persists for at least 5 s
Analysis:  Transfer a volume of the Sample solution, equivalent to 2 mg of ascorbic acid, into 50-mL conical flask. Add 5 mL of metaphosphoric–acetic acids TS, and titrate with Titrant. Correct for the volume of the Titrant consumed by the Blank.
Calculate the percentage of the labeled amount of ascorbic acid (C6H8O6) in the portion of the Tablets taken:
Result = {[(VS VB) × F]/W} × 100
VS== Titrant volume consumed by the Sample solution (mL)
VB== Titrant volume consumed by the Blank (mL)
F== concentration of the Titrant in terms of the equivalent of ascorbic acid (mg/mL)
W== nominal weight of ascorbic acid taken for Analysis (mg)
Acceptance criteria:  90.0%–110.0%
PERFORMANCE TESTS
•  Dissolution 711
Medium:  Water; 900 mL
Apparatus 2:  50 rpm
Time:  45 min
Sample solution:  Withdraw a portion of the solution under test, pass through a suitable filter, and use the pooled sample as the test specimen.
Analysis:  Proceed as directed in the Assay, conducting the procedure without delay and making any necessary modifications.
Calculate the percentage of ascorbic acid dissolved:
Result = (VS VB) × F × [(VM/a)/L] × 100
VS== Titrant volume consumed by the Sample solution (mL)
VB== Titrant volume consumed by the Blank (mL)
F== concentration of the Titrant in terms of the equivalent of ascorbic acid (mg/mL)
VM== volume of Medium, 900 mL
a== volume of the aliquot taken for Analysis
L== labeled amount of ascorbic acid (mg/Tablet)
Tolerances:  NLT 75% (Q) of the labeled amount of ascorbic acid (C6H8O6) is dissolved.
•  Uniformity of Dosage Units 905: Meet the requirements
ADDITIONAL REQUIREMENTS
•  Packaging and Storage: Preserve in tight, light-resistant containers.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Natalia Davydova
Scientific Liaison
1-301-816-8328
(DS2010) Monographs - Dietary Supplements
711 Margareth R.C. Marques, Ph.D.
Senior Scientific Liaison
1-301-816-8106
(GCDF2010) General Chapters - Dosage Forms
USP35–NF30 Page 2244
Pharmacopeial Forum: Volume No. 30(1) Page 60