A: Dissolve about 500mg in 10mLof water in a separator,add 10mLof 3Nhydrochloric acid,and extract the liberated methohexital with two 25-mLportions of chloroform.Evaporate the combined chloroform extracts to dryness,add 10mLof ether,evaporate again,and dry the residue in vacuum at 80for 4hours.Dissolve 50mg of the residue so obtained in 5mLof chloroform:the solution exhibits IRabsorption maxima at the same wavelengths as that of a similar preparation of USP Methohexital RS.

B: The methohexital obtained and dried as directed for Identificationtest Amelts between 92and 96.

Procedure for content uniformity—

Internal standard solution— Dissolve aprobarbital in chloroform to obtain a solution having a concentration of about 1.35mg per mL.

Standard preparation— Dissolve an accurately weighed quantity of USP Methohexital RSin chloroform to obtain a solution having a known concentration of about 0.46mg per mL.Transfer 5.0mLof the resulting solution to a 10-mLvolumetric flask,add 2.0mLof Internal standard solution,dilute with chloroform to volume,and mix to obtain a Standard preparationhaving a known concentration of about 230µg per mL.

Assay preparation— Combine and mix the constituted solutions prepared from the contents of 5vials of Methohexital Sodium for Injection.Transfer an accurately measured volume of the resulting solution,equivalent to about 50mg of methohexital sodium,to a 125-mLseparator containing 25mLof water,and mix.Add 0.2mLof dilute hydrochloric acid (1in 2),and mix.Extract with three 25-mLportions of chloroform,shaking each extraction for 2minutes and filtering the extracts through about 15g of anhydrous sodium sulfate,that previously has been washed with about 5mLof chloroform,into a 100-mLvolumetric flask.Wash the sodium sulfate with several small portions of chloroform,collecting the washings in the 100-mLvolumetric flask.Dilute with chloroform to volume,and mix.Transfer 5.0mLof this solution to a 10-mLvolumetric flask,add 2.0mLof Internal standard solution,dilute with chloroform to volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The gas chromatograph is equipped with a flame-ionization detector and contains a 1.2-m ×4-mm column packed with 3%phase G10on support S1AB.The column is maintained at about 230,the injection port at about 265,and the detector block at about 265.Dry helium is used as the carrier gas at a flow rate of about 60mLper minute.Chromatograph replicate injections of the Standard preparation,and record the peak responses as directed for Procedure:the resolution,R,between methohexital and aprobarbital is not less than 4.0,and the relative standard deviation is not more than 2.0%.

Procedure— Separately inject equal volumes (about 2µL)of the Assay preparationand the Standard preparationinto the gas chromatograph,and measure the peak responses for the major peak.The relative retention times are about 0.6for methohexital and 1.0for aprobarbital.Calculate the quantity,in mg,of methohexital sodium (C14H17N2NaO3)in the portion of Methohexital Sodium for Injection taken by the formula: in which 284.29and 262.30are the molecular weights of methohexital sodium and methohexital,respectively;Cis the concentration,in µg per mL,of USP Methohexital RSin the Standard preparation;and RUand RSare the peak response ratios obtained from the Assay preparationand the Standard preparation,respectively.