Mobile phase and Chromatographic system— Proceed as directed in the Assay under Piperacillin.

Standard piperacillin solution— Proceed as directed in the Related compounds, Test 1 under Piperacillin.

Test solution 1 and Test solution 2— Use Assay preparation 1 and Assay preparation 2, respectively, and proceed as directed under the Assay.

Procedure— Separately inject equal volumes (about 10 µL) of the Test solutions and the Standard piperacillin solution, and proceed as directed in the Assay. Calculate the percentage of piperacillin related compound A and piperacillin related compound C in the portion of Piperacillin for Injection taken by the formula: in which C is the concentration, in mg per mL, of USP Piperacillin RS in the Standard piperacillin solution, P is the designated potency, in µg of piperacillin per mg, of USP Piperacillin RS, A is the quantity, in mg, of piperacillin in each mL of Test solution 1 or Test solution 2, RRFi is the response factor of an individual piperacillin related compound relative to the response of piperacillin, specifically 1.4 for piperacillin related compound A and 0.93 for piperacillin related compound C, ri is the response of each impurity peak, if any, observed in the chromatogram of the Test solution at a retention time corresponding to piperacillin related compound A or piperacillin related compound C, and rSp is the peak response of the piperacillin peak in the chromatogram of the Standard piperacillin solution: not more than 3.5% of piperacillin related compound A and not more than 1.0% of piperacillin related compound C is found.

Mobile phase, Standard preparation, Resolution solution, and Chromatographic system— Proceed as directed in the Assay under Piperacillin.

Assay preparation 1 (where it is labeled for use as a single-dose container)—Constitute Piperacillin for Injection in a volume of water, accurately measured, corresponding to the volume of solvent specified in the labeling. Withdraw all of the withdrawable contents, using a suitable hypodermic needle and syringe, and dilute quantitatively with Mobile phase to obtain a solution containing about 0.4 mg of piperacillin per mL.

Assay preparation 2 (where the label states the quantity of piperacillin in a given volume of the constituted solution)—Constitute Piperacillin for Injection in a volume of water, accurately measured, corresponding to the volume of solvent specified in the labeling. Dilute an accurately measured volume of the constituted solution quantitatively with Mobile phase to obtain a solution containing about 0.4 mg of piperacillin per mL.

Procedure— Separately inject equal volumes (about 10 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 piperacillin (C23H27N5O7S) in the container, or in the portion of constituted solution taken by the formula: in which L is the labeled quantity, in mg, of piperacillin in the container or in the volume of constituted solution taken, D is the concentration, in mg of piperacillin per mL, of Assay preparation 1 or Assay preparation 2, based on the labeled quantity in the container or in the portion of constituted solution taken, respectively, and the extent of dilution, C is the concentration, in mg per mL, of USP Piperacillin RS in the Standard preparation, P is the designated potency, in µg of piperacillin per mg, of USP Piperacillin RS, and rU and rS are the piperacillin peak responses obtained from the Assay preparation and the Standard preparation, respectively.