A: Ultraviolet Absorption á197Uñ—

Solution: 50µg per mL.

Medium: water.

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

C: It responds to the tests for Sodium á191ñ.

Acetic acid solution— Prepare a 1in 20solution of glacial acetic acid and water.

0.05M Sodium acetate— Dissolve 6.8g of sodium acetate in about 800mLof water,adjust with Acetic acid solutionto a pHof 7.5,dilute with water to 1000mL,and mix.

Mobile phase— Prepare a suitable filtered and degassed mixture of 0.05M Sodium acetateand acetonitrile (70:30).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Diluent— Dissolve 6.9g of sodium citrate in about 800mLof water,adjust with 1Nhydrochloric acid to a pHof 7.0,dilute with water to 1000mL,and mix.

Standard preparation— Dissolve an accurately weighed quantity of USP Nafcillin Sodium RSquantitatively in Diluentto obtain a solution having a known concentration of about 400µg of nafcillin (C21H22N2O5S)per mL.

Resolution solution— Prepare a solution of orcinol in water containing about 35mg per mL.Add 0.5mLof this solution to 25mLof Standard preparationto obtain a solution containing about 0.7mg of orcinol and 400µg of nafcillin per mL.

Assay preparation— Transfer about 88mg of Nafcillin Sodium,accurately weighed,to a 200-mLvolumetric flask,dilute with Diluentto volume,and mix.

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 1mLper minute.Chromatograph the Resolution solution,and record the peak responses as directed for Procedure:the relative retention times are about 0.8for orcinol and 1.0for nafcillin;and the resolution between the orcinol and nafcillin peaks is not less than 2.0.Chromatograph the Standard preparation,and record the responses as directed for Procedure:the tailing factor for the analyte peak is not more than 1.5;and the relative standard deviation for replicate injections 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 µg,of nafcillin (C21H22N2O5S)in each mg of Nafcillin Sodium taken by the formula: in which Cis the concentration,in µg per mL,of nafcillin (C21H22N2O5S)in the Standard preparation;Wis the weight,in mg,of the portion of Nafcillin Sodium taken;and rUand rSare the nafcillin peak responses obtained from the Assay preparationand the Standard preparation,respectively.