Assay—
Mobile phase—
Prepare a suitable degassed solution of water,acetonitrile,and glacial acetic acid (86:13:1)such that the relative retention times of sulfadiazine,sulfamerazine,and sulfamethazine are approximately 0.6,0.8,and 1.0,respectively.(If the retention times are excessive,the concentration of acetonitrile may be increased.)
Standard preparation—
Transfer 33mg each of
USP Sulfadiazine RS,
USP Sulfamerazine RS,and
USP Sulfamethazine RS,accurately weighed,to a 100-mLvolumetric flask,dissolve in 25mLof 0.1Nsodium hydroxide,dilute with water to volume,and mix.Pipet 3mLinto a 25-mLvolumetric flask,dilute with water to volume,and mix to obtain a
Standard preparationhaving a known concentration of about 40µg of each USP Reference Standard per mL.
Assay preparation—
Determine the specific gravity of the Oral Suspension,using a tared,50-mLvolumetric flask,by weighing 50mLof Oral Suspension that previously has been shaken in the original container to ensure homogeneity,allowed to stand long enough for entrapped air to rise,and finally inverted carefully just prior to transfer to the volumetric flask.Transfer an accurately weighed quantity of Oral Suspension,well-shaken and free from entrapped air,equivalent to about 100mg of total sulfapyrimidines,to a 100-mLvolumetric flask,add 25mLof 0.1Nsodium hydroxide,and swirl for several minutes to dissolve the sulfapyrimidines.Dilute with water to volume,and mix.Filter the mixture,discarding the first several mLof the filtrate.Pipet 3mLof the clear filtrate into a 25-mLvolumetric flask,dilute with water to volume,and mix.
Chromatographic system(see Chromatography á621ñ)—
The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm ×30-cm column that contains packing L1.The flow rate is about 2mLper minute.Chromatograph five replicate injections of the
Standard preparation,and record the peak responses as directed for
Procedure:the relative standard deviation is not more than 2.0%,and the resolution factors between sulfadiazine and sulfamerazine and between sulfamerazine and sulfamethazine are each not less than 3.0.
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.The relative retention times for sulfadiazine,sulfamerazine,and sulfamethazine are approximately 0.6,0.8,and 1.0,respectively.Calculate the quantity,in mg,of sulfadiazine in the portion of Oral Suspension taken by the formula:
0.833C(RU/RS),
in which
Cis the concentration,in µg per mL,of
USP Sulfadiazine RSin the
Standard preparation;and
RUand
RSare the peak responses obtained from the
Assay preparationand the
Standard preparation,respectively.Similarly measure the responses of the sulfamerazine and sulfamethazine peaks,and calculate the quantity,in mg,of each in the portion of Oral Suspension taken.