A: Infrared Absorption 197K.

B: Ultraviolet Absorption 197U—

C: A solution (1 in 20) responds to the tests for Sodium 191.

Test solution: 10 mg per mL, in pH 6.4 sodium phosphate buffer, prepared as directed in the Assay.

pH 4.3 sodium phosphate buffer— Dissolve 13.8 g of monobasic sodium phosphate in 900 mL of water, adjust with phosphoric acid or 10 N sodium hydroxide to a pH of 4.3 ± 0.1, dilute with water to make 1000 mL, and mix.

Mobile phase— Prepare a suitable mixture of pH 4.3 sodium phosphate buffer and acetonitrile (95:5), and pass through a membrane filter of 0.5-µm or finer porosity. Make adjustments if necessary (see System Suitability under Chromatography 621).

pH 6.4 sodium phosphate buffer— Dissolve 6.9 g of monobasic sodium phosphate in 900 mL of water, adjust with 10 N sodium hydroxide to a pH of 6.4 ± 0.1, dilute with water to make 1000 mL, and mix.

Standard preparation— Transfer about 50 mg of USP Ticarcillin Monosodium Monohydrate RS, accurately weighed, to a 50-mL volumetric flask, dilute with pH 6.4 sodium phosphate buffer to volume, and mix.

Resolution solution— Transfer about 25 mg of USP Ticarcillin Monosodium Monohydrate RS, accurately weighed, to a 25-mL volumetric flask. Prepare a solution of USP Clavulanate Lithium RS in pH 6.4 sodium phosphate buffer containing the equivalent of about 0.15 mg of clavulanic acid per mL. Place 5 mL of this solution in the 25-mL volumetric flask, dilute with pH 6.4 sodium phosphate buffer to volume, and mix. [note—Use this solution on the day prepared.]

Assay preparation— Transfer about 50 mg of Ticarcillin Monosodium, accurately weighed, to a 50-mL volumetric flask, dilute with pH 6.4 sodium phosphate buffer to volume, and mix.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 220-nm detector and a 4-mm × 30-cm column that contains 3- to 10-µm packing L1. The flow rate is about 2 mL per minute. Chromatograph the Resolution solution, and record the peak responses as directed for Procedure: the relative retention times are about 0.2 for clavulanic acid and 1.0 for ticarcillin; and the resolution, R, between the clavulanic acid peak and the ticarcillin peak is not less than 5.0. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the column efficiency is not less than 1000 theoretical plates; the tailing factor is not more than 2.0; 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 ticarcillin (C15H16N2O6S2) in each mg of the Ticarcillin Monosodium taken by the formula: in which C is the concentration, in mg per mL, of USP Ticarcillin Monosodium Monohydrate RS in the Standard preparation; P is the designated potency, in µg of ticarcillin (C15H16N2O6S2) per mg, of USP Ticarcillin Monosodium Monohydrate RS; W is the weight, in mg, of Ticarcillin Monosodium taken to prepare the Assay preparation; and rU and rS are the ticarcillin peak responses obtained from the Assay preparation and the Standard preparation, respectively.