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.
Clavulanate lithium stock standard solution—
Dissolve an accurately weighed quantity of
USP Clavulanate Lithium RS in
pH 6.4 sodium phosphate buffer to obtain a solution having a known concentration of about 0.6 mg per mL.
Standard preparation—
Transfer about 100 mg of
USP Ticarcillin Monosodium Monohydrate RS, accurately weighed, to a 100-mL volumetric flask, add 150/
J mL of
Clavulanate lithium stock standard solution, accurately measured,
J being the ratio of the labeled amount, in mg, of ticarcillin to the labeled amount, in mg, of clavulanic acid in the Ticarcillin Disodium and Clavulanic Acid for Injection, dilute with
pH 6.4 sodium phosphate buffer to volume, and mix.
Assay preparation—
Dissolve the contents of 1 container of Ticarcillin and Clavulanic Acid for Injection in a volume of water, accurately measured, corresponding to the volume of solvent specified in the labeling. Using a suitable hypodermic needle and syringe, remove all of the withdrawable contents from the container, and dilute quantitatively and stepwise with pH 6.4 sodium phosphate buffer to obtain a solution having a concentration of about 0.9 mg of ticarcillin (C15H16N2O6S2) per mL.
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
Standard preparation, 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; the column efficiency determined from the analyte peaks is not less than 1000 theoretical plates; the tailing factors for the analyte peaks are not more than 2.0; the resolution,
R, between the ticarcillin and clavulanic acid peaks is not less than 5.0; 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 preparations into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of ticarcillin (C
15H
16N
2O
6S
2) in the container of Ticarcillin and Clavulanic Acid for Injection taken by the formula:
(L / D)(CP / 1000)(rU / rS),
in which
L is the labeled quantity, in mg, of ticarcillin in the container;
D is the concentration, in mg per mL, of ticarcillin in the
Assay preparation on the basis of the labeled quantity of ticarcillin in the container and the extent of dilution;
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 per mg, of
USP Ticarcillin Monosodium Monohydrate RS; and
rU and
rS are the ticarcillin peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
Calculate the quantity, in mg, of clavulanic acid (C8H9NO5) in the container of Ticarcillin and Clavulanic Acid for Injection taken by the formula:
(L / D)(CP / 1000)(rU / rS),
in which
L is the labeled quantity, in mg, of clavulanic acid in the container;
D is the concentration, in mg per mL, of clavulanic acid in the
Assay preparation on the basis of the labeled quantity of clavulanic acid in the container and the extent of dilution;
C is the concentration, in mg per mL, of
USP Clavulanate Lithium RS in the
Standard preparation; P is the designated potency, in µg of clavulanic acid per mg, of
USP Clavulanate Lithium RS; and
rU and
rS are the clavulanic acid peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
