A: Infrared Absorption á197Kñ.

B: Ultraviolet Absorption á197Uñ—

Solution: 20µg per mL.

Medium: water.

Ratio: A245/A262,between 0.63and 0.67.

Mobile phase— Prepare a filtered and degassed solution containing 0.005Msodium 1-heptanesulfonate and methanol (70:30).

Standard preparation— Transfer about 50mg of USP Niacinamide RS,accurately weighed,to a 100-mLvolumetric flask,dissolve in about 3mLof water,dilute with Mobile phaseto volume,and mix.Dilute 4.0mLof the resulting solution with Mobile phaseto 50.0mL,and mix.

Resolution solution— Prepare a solution containing equal volumes of the Standard preparationand of a niacin solution similarly prepared and having the same concentration.

Assay preparation— Prepare as directed under Standard preparation,using Niacinamide instead of the Reference Standard.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm ×30-cm column containing packing L1.The flow rate is about 2mLper minute.Chromatograph the Resolution solution:the resolution,R,between the niacin and niacinamide peaks is not less than 3.0.Chromatograph replicate injections of the Standard preparation,and record the peak responses as directed for Procedure:the relative standard deviation is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C6H6N2Oin the portion of Niacinamide taken by the formula: in which Cis the concentration,in mg per mL,of USP Niacinamide RSin the Standard preparation,and rUand rSare the peak responses for the Assay preparationand the Standard preparation,respectively.