A: Triturate a quantity of finely powdered Tablets,equivalent to about 1g of hydroxychloroquine sulfate,with 50mLof water,and filter:the clear filtrate so obtained meets the requirements for Identificationtests Band C.

B: It meets the requirements under Identification—Organic Nitrogenous Bases á181ñ.

C: Asolution (1in 100)meets the requirements of the tests for Sulfate á191ñ.

D: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.

Medium: water;900mL.

Apparatus 2: 50rpm.

Time: 60minutes.

Procedure— Determine the amount of C18H26ClN3O·H2SO4dissolved from UVabsorbances at the wavelength of maximum absorbance at about 343nm 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 USP Hydroxychloroquine Sulfate RSin the same medium.

Tolerances— Not less than 70%(Q)of the labeled amount of C18H26ClN3O·H2SO4is dissolved in 60minutes.

Mobile phase— To 800mLof water,add 100mLof methanol,100mLof acetonitrile,2.0mLof phosphoric acid,and 96mg of sodium 1-pentanesulfonate,mix,and filter.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Solvent mixture— Prepare a mixture of methanol and water (1:1).

Standard preparation— Dissolve an accurately weighed quantity of USP Hydroxychloroquine Sulfate RSin Solvent mixture,dilute quantitatively with Solvent mixture,and mix to obtain Solution Ahaving a known concentration of about 1mg per mL.Transfer 5.0mLof this solution to a 100-mLvolumetric flask,dilute with Mobile phaseto volume,and mix to obtain the Standard preparationhaving a known concentration of about 0.05mg per mL.

Resolution solution— Prepare a solution of chloroquine phosphate in methanol having a concentration of 1mg per mL.Transfer 5.0mLof this solution to a 100-mLvolumetric flask,add 5.0mLof Solution A,dilute with Mobile phaseto volume,and mix.

Assay preparation— Weigh and finely powder not less than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 200mg of hydroxychloroquine sulfate to a 200-mLvolumetric flask,add about 150mLof Solvent mixture,and mix.Sonicate,with intermittent shaking,for about 15minutes,and cool to room temperature.Dilute with Solvent mixtureto volume,mix,and filter.Transfer 5.0mLof this solution to a 100-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm ×25-cm column that contains 5-to 10-µm packing L1.The flow rate is about 1.0mLper minute.Chromatograph about 20µLof the Resolution solution,and record the peak responses as directed under Procedure:the resolution,R,between chloroquine and hydroxychloroquine is not less than 1.8.Chromatograph replicate injections of the Standard preparation,and record the peak responses as directed under Procedure:the relative standard deviation is not more than 1.5%.

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 hydroxychloroquine sulfate (C18H26ClN3O·H2SO4)in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Hydroxychloroquine Sulfate RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.