A: Heat a quantity of finely powdered Tablets,equivalent to about 500mg of niacin,with 25mLof alcohol on a steam bath for a few minutes,filter,and wash the residue with a few mLof hot alcohol.To the filtrate add 30mLof water,and evaporate to about 25mLon the steam bath.Cool,filter if insoluble matter separates,and evaporate the filtrate to about 10mL.Cool,and place in a refrigerator for 1hour.Filter the separated niacin with suction,wash it with a few mLof cold alcohol,and dry at 105for 1hour:the niacin so obtained responds to Identificationtests Aand Bunder Niacin.

B: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparationobtained as directed in the Assay.

Medium: 0.1Nhydrochloric acid;900mL.

Apparatus 1: 100rpm.

Time: 60minutes.

Procedure— Determine the amount of C6H5NO2dissolved from UVabsorbances at the wavelength of maximum absorbance at about 260nm of filtered portions of the solution under test,suitably diluted with Dissolution Medium,if necessary,in comparison with a Standard solution having a known concentration of about 0.02mg of USP Niacin RSper mLin the same medium.

Tolerances— Not less than 65%(Q)of the labeled amount of C6H5NO2is dissolved in 60minutes.

Mobile phase— Prepare a 0.005Msolution of sodium 1-hexanesulfonate in water.Mix 78parts of this solution with 14parts of methanol,7parts of acetonitrile,and 1part of glacial acetic acid,stir,filter,and degas.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Transfer an accurately weighed quantity of USP Niacin RSto a suitable volumetric flask,add water,heat on a steam bath,sonicate,shake by mechanical means,cool,and dilute with water to volume to obtain a solution having a known concentration of about 0.5mg per mL.Transfer 1.0mLof this solution to a 10-mLvolumetric flask,dilute with water to volume,and mix.

Assay preparation— Weigh and finely powder not less than 20Tablets.Transfer an accurately weighed quantity of the powder equivalent to about 500mg of Niacin to a 100-mLvolumetric flask,add 50mLof water,and heat on a steam bath for 30minutes.Sonicate for 2minutes,shake by mechanical means for 15minutes,and cool to room temperature.Dilute with water to volume,mix,and filter.Transfer 1.0mLof this solution to a 100-mLvolumetric flask,dilute with water to volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 262-nm detector and a 4-mm ×30-cm column that contains packing L1.The flow rate is about 1.3mLper minute.Chromatograph replicate injections of the Standard preparation,and record the peak responses as directed for Procedure:the column efficiency determined from the analyte peak is not less than 1000theoretical plates,the tailing factor for the analyte peak is not more than 2.0,and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— [NOTE—Use peak areas where peak responses are indicated.]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 C6H5NO2in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Niacin RSin the Standard preparation,and rUand rSare the peak responses for niacin obtained from the Assay preparationand the Standard preparation,respectively.