Water,Method Iá921ñ
Proceed as directed in the chapter,except to use the following modifications.Use a mixture of anhydrous formamide and methanol (1:1)in place of methanol as the titration vessel solvent.The
Reagentvolume required in order to condition the titration vessel solvent is not greater than 10%of the initial volume of solvent.The concentration of Ganciclovir for Injection in the titration vessel is not greater than 7mg per mL.Not more than 3.0%is found.
Assay
Mobile phase
Dissolve 1.4g of monobasic ammonium phosphate and 2.0g of phosphoric acid in 500mLof water in a 1000-mLvolumetric flask.Dilute with water to volume,mix,filter,and degas.Make adjustments if necessary (see
System Suitabilityunder
Chromatography á621ñ).
Internal standard solution
Transfer about 75mg of hypoxanthine to a 500-mLvolumetric flask,dissolve in and dilute with water to volume,and mix.
Standard stock preparation
Dissolve an accurately weighed amount of
USP Ganciclovir RSin water to obtain a solution having a known concentration of about 250µg per mL.
Standard preparation
Transfer 20.0mLof the Standard stock preparationand 10.0mLof the Internal standard solutionto a 100-mLvolumetric flask.Dilute with Mobile phaseto volume,and mix.
Assay stock preparation
Constitute Ganciclovir for Injection in a portion of water,quantitatively transfer with water to a suitable volumetric flask,and dilute with water to volume to obtain a solution having a concentration of about 1mg per mL.
Assay preparation
Transfer 5.0mLof the Assay stock preparationand 10.0mLof the Internal standard solutionto a 100-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.
Chromatographic system (see Chromatography á621ñ)
The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm ×10-cm column that contains packing L1.The flow rate is about 1.2mLper minute.Chromatograph the
Standard preparation,and record the peak responses as directed for
Procedure:the relative retention times are about 0.7for hypoxanthine and 1.0for ganciclovir;the resolution,
R,between hypoxanthine and ganciclovir is not less than 3.0;the column efficiency is not less than 1000theoretical 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 10µL)of the
Standard preparationand the
Assay preparationinto the chromatograph,record the chromatograms,and measure the peak response ratios for the major peaks.Calculate the quantity,in mg,of ganciclovir (C
9H
13N
5O
4)in the container of Ganciclovir for Injection taken by the formula:
CD(RU/RS),
in which
Cis the concentration,in mg per mL,of
USP Ganciclovir RSin the
Standard preparation;Dis the dilution factor,in mL,used to prepare the
Assay preparation;and
RUand
RSare the peak response ratios of ganciclovir to the internal standard obtained from the
Assay preparationand the
Standard preparation,respectively.