A: Ultraviolet Absorption 197U—

Solution: 50 µg per mL.

Medium: water.

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

C: It responds to the tests for Sodium 191.

(Official January 1, 2007)

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

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

Mobile phase— Prepare a suitable filtered and degassed mixture of 0.05 M Sodium acetate and acetonitrile (70:30). Make adjustments if necessary (see System Suitability under Chromatography 621).

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

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

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

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

Chromatographic system (see Chromatography 621)—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 1 mL per minute. Chromatograph the Resolution solution, and record the peak responses as directed for Procedure: the relative retention times are about 0.8 for orcinol and 1.0 for 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 20 µL) of the Standard preparation and the Assay preparation into 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 C is the concentration, in µg per mL, of nafcillin (C21H22N2O5S) in the Standard preparation; W is the weight, in mg, of the portion of Nafcillin Sodium taken; and rU and rS are the nafcillin peak responses obtained from the Assay preparation and the Standard preparation, respectively.