A:Infrared Absorption á197Mñ.

B:Ultraviolet Absorption á197Uñ—

Test solution: 5mg per mL,in acetonitrile.

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile and 0.01Mphosphoric acid (13:7).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

System suitability solution— Dissolve accurately weighed quantities of USP Lovastatin RSand USP Lovastatin Related Compound A RSin acetonitrile,and dilute quantitatively,and stepwise if necessary,to obtain a solution containing 2.0µg of each per mL.

Standard solution— Dissolve an accurately weighed quantity of USP Lovastatin RSin acetonitrile,and dilute quantitatively,and stepwise if necessary,to obtain a solution having a known concentration of about 2.0µg per mL.

Test solution— Transfer about 25mg of Lovastatin,accurately weighed,to a 25-mLvolumetric flask,dissolve in and dilute with acetonitrile to volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 200-nm detector and a 4.6-mm ×25-cm column that contains 5-µm packing L7.The column temperature is maintained at 40.The flow rate is about 1.5mLper minute.Chromatograph the System suitability solution,and record the peak responses as directed for Procedure:the relative retention times are about 1.0for lovastatin and 1.3for lovastatin related compound A;and the resolution,R,between lovastatin and lovastatin related compound Ais not less than 6.0.Chromatograph the Standard solution,and record the peak responses as directed for Procedure:the relative standard deviation for replicate injections is not more than 5.0%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure all the peak responses.Calculate the percentage of lovastatin related compound Ain the portion of Lovastatin taken by the formula: in which Fis the response factor for lovastatin related compound Aand is equal to 1.6;Cis the concentration,in µg per mL,of USP Lovastatin RSin the Standard solution;Wis the weight,in mg,of Lovastatin in the Test solution;rUis the peak response for lovastatin related compound Aobtained from the Test solution;and rSis the peak response for lovastatin obtained from the Standard solution:not more than 0.5%of lovastatin related compound Ais found.

Solution A— Prepare a 0.001Mphosphoric acid solution,adjusted with 1Msodium hydroxide to a pHof 4.0.

Solution B— Use acetonitrile.

Mobile phase— Use variable mixtures of Solution Aand Solution Bas directed for Chromatographic system.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

System suitability solution— Dissolve accurately weighed quantities of USP Lovastatin RSand compactin in acetonitrile,and dilute quantitatively,and stepwise if necessary,with acetonitrile to obtain a solution containing 2.0µg of each per mL.

Standard solution— Dissolve an accurately weighed quantity of USP Lovastatin RSin acetonitrile,and dilute quantitatively,and stepwise if necessary,to obtain a solution having a known concentration of about 2.0µg per mL.

Test solution— Transfer about 25mg of Lovastatin,accurately weighed,to a 25-mLvolumetric flask,dissolve in and dilute with acetonitrile to volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 238-nm detector and a 4.0-mm ×12.5-cm column that contains 4-µm packing L1.The column temperature is maintained at 40.The flow rate is about 1.5mLper minute.The chromatograph is programmed as follows. Chromatograph the System suitability solutionand the Standard solution,and record the peak responses as directed for Procedure:the relative retention times are about 1.00for lovastatin and 0.85for compactin;the resolution,R,between lovastatin and compactin is not less than 3.5;and the relative standard deviation for replicate injections is not more than 5%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure all the peak responses.Calculate the percentage of each impurity in the portion of Lovastatin taken by the formula: in which Cis the concentration,in µg per mL,of USP Lovastatin RSin the Standard solution;Wis the weight,in mg,of Lovastatin in the Test solution;riis the peak response for each impurity obtained from the Test solution;rSis the peak response for lovastatin obtained from the Standard solution;and Fis the response factor for each impurity and is equal to 1.4for the impurity with a relative retention time of about 0.73and 1.0for all other impurities.Disregard any peak with less than 0.04%:not more than 0.2%of any individual impurity is found;and not more than 1.0%of total impurities is found.

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile and 0.1%phosphoric acid solution (65:35).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Lovastatin RSin acetonitrile to obtain a solution having a known concentration of about 0.3mg per mL.

Assay preparation— Transfer about 30mg of Lovastatin,accurately weighed,to a 100-mLvolumetric flask,dissolve in and dilute with acetonitrile to volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 238-nm detector and a 4.6-mm ×25-cm column that contains 5-µm packing L7.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the column efficiency is not less than 3000theoretical plates,the tailing factor is not more than 1.4,and the relative standard deviation for replicate injections is not more than 1.0%.

Procedure— Separately inject equal volumes (about 10µL)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 C24H36O5in the portion of Lovastatin taken by the formula: in which Cis the concentration,in mg per mL,of USP Lovastatin RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.