Solution: Dilute a portion of the Injectable Suspension with methanol to obtain a solution having a concentration of about 20µg per mL.

Mobile solvent— Prepare a mixture of isooctane,tetrahydrofuran,and alcohol (89:10:8).

Standard preparation— Dissolve an accurately weighed quantity of USP Prednisolone Tebutate RSin a mixture of tetrahydrofuran and isooctane (1:1)to obtain a solution having a known concentration of about 1mg per mL.

Assay preparation— Transfer to a separator an accurately measured volume,freshly mixed,of Injectable Suspension,equivalent to about 100mg of prednisolone tebutate,and dilute with about 10mLof water.Extract with three 25-mLportions of methylene chloride,filtering each portion through methylene chloride-washed cotton into a 100-mLvolumetric flask.Add methylene chloride to volume,and mix.Pipet 10mLof this solution into a 50-mLcentrifuge tube,evaporate the methylene chloride on a steam bath just to dryness,cool,and dissolve the residue in 10.0mLof tetrahydrofuran and isooctane (1:1).Filter through a 1-µm membrane filter.

Procedure— Introduce equal volumes,about 10µL,of the Assay preparationand the Standard preparationinto a high-pressure liquid chromatograph (see Chromatography á621ñ),operated at room temperature,by means of a suitable microsyringe or sampling valve,adjusting the sample size and other operating parameters such that the peak obtained with the Standard preparationis about 0.6full-scale.Typically,the apparatus is fitted with a 3.9-mm ×30-cm column containing packing L3and is equipped with an UVdetector capable of monitoring absorption at 254nm and a suitable recorder.In a suitable chromatogram,the coefficient of variation for five replicate injections of a single specimen is not more than 3.0%.Measure the height of the peaks,at identical retention times,obtained with the Assay preparationand the Standard preparation.Calculate the quantity,in mg,of C27H38O6,in the volume of Injectable Suspension taken by the formula: in which Cis the concentration,in mg per mL,of USP Prednisolone Tebutate RSin the Standard preparation,and rUand rSare the peak heights obtained from the Assay preparationand the Standard preparation,respectively.