(nye' a sin).
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C6H5NO2 123.11
3-Pyridinecarboxylic acid;    
Nicotinic acid     [59-67-6].
Niacin contains NLT 99.0% and NMT 101.0% of niacin (C6H5NO2), calculated on the dried basis.
•  B. Ultraviolet Absorption 197U
Wavelength range:  200–300 nm
Sample solution:  20 µg/mL in Buffer solution, prepared as directed in the Assay
Acceptance criteria:  Meets the requirements in the chapter. The A237/A262 ratio is 0.46–0.50.
•  Procedure
Buffer solution:  Dissolve 6.8 g of monobasic potassium phosphate in 1000 mL of water. Adjust with 50% sodium hydroxide solution to a pH of 7.0.
Standard solution:  0.02 mg/mL of USP Niacin RS in Buffer solution
Sample solution:  0.02 mg/mL of Niacin in Buffer solution
Blank:  Buffer solution
Instrumental conditions 
Mode:  UV-Vis
Analytical wavelength:  262 nm
Cell:  1 cm
Samples:  Standard solution, Sample solution, and Blank
Determine the absorbances of the solutions against the Blank.
Calculate the percentage of niacin (C6H5NO2) in the portion of Niacin taken:
Result = (AU/AS) × (CS/CU) × 100
AU== absorbance of the Sample solution
AS== absorbance of the Standard solution
CS== concentration of USP Niacin RS in the Standard solution (µg/mL)
CU== concentration of Niacin in the Sample solution (µg/mL)
Acceptance criteria:  99.0%–101.0% on the dried basis
•  Residue on Ignition 281: NMT 0.1%
•  Chloride and Sulfate, Chloride 221
Standard:  0.15 mL of 0.020 N hydrochloric acid
Sample:  0.50 g of Niacin
Acceptance criteria:  NMT 0.02%
•  Chloride and Sulfate, Sulfate 221
Standard:  0.10 mL of 0.020 N sulfuric acid
Sample:  0.50 g of Niacin
Acceptance criteria:  NMT 0.02%
•  Heavy Metals, Method I 231
Test preparation:  Mix 1 g with 4 mL of 1 N acetic acid, and dilute with water to 25 mL. Heat gently until solution is complete, and cool.
Acceptance criteria:  NMT 20 ppm
•  Ordinary Impurities 466
Standard solutions and Test solution:  Use water as the solvent.
Eluant:  A mixture of methanol and 0.1 N hydrochloric acid (9:1)
Visualization:  1
Analysis:  Proceed as directed in the chapter.
Acceptance criteria:  NMT 2.0% of total ordinary impurities
•  Loss on Drying 731: Dry a sample at 105 for 1 h: it loses NMT 1.0% of its weight.
•  Packaging and Storage: Preserve in well-closed containers.
•  USP Reference Standards 11
USP Niacin 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.
Scientific Liaison
(DS2010) Monographs - Dietary Supplements
Reference Standards RS Technical Services
USP35–NF30 Page 4042
Pharmacopeial Forum: Volume No. 29(6) Page 1937