Sodium Ascorbate
(soe' dee um a skor' bate).
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C6H7NaO6 198.11
l-Ascorbic acid, monosodium salt;    
Monosodium l-ascorbate     [134-03-2].
DEFINITION
Sodium Ascorbate contains NLT 99.0% and NMT 101.0% of sodium ascorbate (C6H7NaO6), calculated on the dried basis.
IDENTIFICATION
•  A. Infrared Absorption 197M
Sample:  Use undried Sodium Ascorbate.
Acceptance criteria:  Meets the requirements
•  B. Reducing capacity
Sample solution:  20 mg/mL
Analysis:  Add 1 mL of 0.1 N hydrochloric acid to 4 mL of the Sample solution, and add alkaline cupric tartrate TS.
Acceptance criteria:  The solution reduces alkaline cupric tartrate TS slowly at room temperature, but more readily upon heating.
•  C. Identification Tests—General, Sodium 191: A 20-mg/mL solution meets the requirements.
ASSAY
•  Procedure
Sample:  400 mg of Sodium Ascorbate
Blank:  100 mL of carbon dioxide-free water and 25 mL of 2 N sulfuric acid
Titrimetric system 
Mode:  Direct titration
Titrant:  0.1 N iodine VS
Endpoint detection:  Visual
Analysis:  Dissolve the Sample in a mixture of 100 mL of carbon dioxide-free water and 25 mL of 2 N sulfuric acid. Titrate immediately with the Titrant, and add 3 mL of starch TS as the endpoint is approached. Perform the Blank determination.
Calculate the percentage of sodium ascorbate (C6H7NaO6) in the portion of Sodium Ascorbate taken:
Result = {[(VS VB) × N × F]/W} × 100
VS== Titrant volume consumed by the Sample (mL)
VB== Titrant volume consumed by the Blank (mL)
N== actual normality of the Titrant (mEq/mL)
F== equivalency factor, 99.05 mg/mEq
W== Sample weight (mg)
Acceptance criteria:  99.0%–101.0% on the dried basis
IMPURITIES
•  Heavy Metals, Method II 231: NMT 20 ppm
SPECIFIC TESTS
•  Optical Rotation, Specific Rotation 781S
Sample solution:  100 mg/mL in carbon dioxide-free water. Use the solution immediately after preparation.
Acceptance criteria:  +103 to +108
•  pH 791
Sample solution:  100-mg/mL solution
Acceptance criteria:  7.0–8.0
•  Loss on Drying 731: Dry a sample in a suitable vacuum drying tube, using phosphorus pentoxide as the desiccant, at 60 for 4 h: it loses NMT 0.25% of its weight.
ADDITIONAL REQUIREMENTS
•  Packaging and Storage: Preserve in tight, light-resistant containers.
•  USP Reference Standards 11
USP Sodium Ascorbate RS Click to View Structure
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Huy T. Dinh, M.S.
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(DS2010) Monographs - Dietary Supplements
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USP35–NF30 Page 4646