Assay
pH7buffer
Dissolve 42.59g of anhydrous dibasic sodium phosphate and 27.22g of monobasic potassium phosphate in water to make 1000mLof solution.
Mobile phase
Mix 40mLof acetonitrile and 200mLof
pH7buffer,and dilute with water to obtain 2000mLof solution.Filter,using a filter having a porosity of 1µm or finer,and degas.Make adjustments if necessary (see
System Suitability under
Chromatography á621ñ).
Standard preparation
Transfer about 29mg of
USP Ceftazidime Pentahydrate RS,accurately weighed,to a 25-mLvolumetric flask containing 2.5mLof
pH7buffer,and shake until dissolved.Dilute with water to volume,and mix.
[NOTEProtect this solution from light.
]Immediately prior to chromatography,transfer 5.0mLof this stock solution to a 50-mLvolumetric flask,dilute with water to volume,and mix.This solution contains about 100µg of ceftazidime (C
22H
22N
6O
7S
2)per mL.
Assay preparation
Transfer about 115mg of Ceftazidime,accurately weighed,to a 100-mLvolumetric flask containing 10.0mLof pH7buffer,and shake until dissolved.Dilute with water to volume,and mix.[NOTEProtect this solution from light.]Immediately prior to chromatography,transfer 5.0mLof this solution to a 50-mLvolumetric flask,dilute with water to volume,and mix.
Resolution solution
Prepare a solution of USP Delta-3-Ceftazidime Isomer RSin pH7buffercontaining about 0.1mg per mL.Immediately prior to chromatography,mix 1mLof this solution with 8mLof water and 1mLof the stock solution used to prepare the Standard preparation.
Chromatographic system
(see
Chromatography á621ñ)The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm ×15-cm column that contains 5-µm packing L1.The flow rate is about 2mLper minute.Chromatograph the
Resolution solution,and record the peak responses as directed for
Procedure:the resolution,
R,between the ceftazidime and the delta-3-ceftazidime isomer 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 less than 0.75and not more than 1.5,and the relative standard deviation for replicate injections is not more than 1.0%.
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 mg,of C
22H
22N
6O
7S
2in the portion of Ceftazidime taken by the formula:
C(rU/rS),
in which
Cis the concentration,in µg per mL,of ceftazidime (C
22H
22N
6O
7S
2)in the
Standard preparation,and
rUand
rSare the peak responses obtained from the
Assay preparationand the
Standard preparation,respectively.