Thiopental Sodium, chemical structure, molecular formula, Reference Standards
»Thiopental Sodium contains not less than 97.0percent and not more than 102.0percent of C11H17N2NaO2S,calculated on the dried basis.
Packaging and storage
Preserve in tight containers.
USP Reference standards á11ñ
USP Thiopental RS.
Dissolve about 500mg in 10mLof water in a separator,add 10mLof 3Nhydrochloric acid,and extract the liberated thiopental with two 25-mLportions of chloroform.Evaporate the combined chloroform extracts to dryness.Add 10mLof ether,evaporate again,and dry at 105for 2hours:the IRabsorption spectrum of a potassium bromide dispersion of the residue so obtained exhibits maxima only at the same wavelengths as that of a similar preparation of USP Thiopental RS.
Ignite about 500mg:the residue responds to the tests for Sodium á191ñ.
Dissolve about 200mg in 5mLof 1Nsodium hydroxide,and add 2mLof lead acetate TS:a white precipitate is formed,and it gradually darkens when the mixture is boiled.Acidify the darkened mixture with hydrochloric acid:hydrogen sulfide is evolved,and it is recognizable by its darkening of moistened lead acetate test paper held in the vapor.
Loss on drying á731ñ
Dry it at 80for 4hours:it loses not more than 2.0%of its weight.
Heavy metals,Method IIá231ñ:
Ordinary impurities á466ñ
10mg of Thiopental Sodium per mLof methanol.
9.2mg of USP Thiopental RSper mLof methanol.
a mixture of toluene and methanol (85:15).
Transfer about 100mg of Thiopental Sodium,accurately weighed,to a 200-mLvolumetric flask,add sodium hydroxide solution (1in 250)to volume,and mix.Pipet 5mLof the solution into a 500-mLvolumetric flask,add sodium hydroxide solution (1in 250)to volume,and mix.Dissolve an accurately weighed quantity of USP Thiopental RSin sodium hydroxide solution (1in 250),and dilute quantitatively and stepwise with sodium hydroxide solution (1in 250)to obtain a Standard solution having a known concentration of about 5µg per mL.Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 304nm,with a suitable spectrophotometer,using sodium hydroxide solution (1in 250)as the blank.Calculate the quantity,in mg,of C11H17N2NaO2Sin the Thiopental Sodium taken by the formula:
in which Cis the concentration,in µg per mL,of USP Thiopental RSin the Standard solution,1.091is the ratio of the molecular weight of thiopental sodium to that of thiopental,and AUand ASare the absorbances of the solution of Thiopental Sodium and the Standard solution,respectively.
Staff Liaison:Karen A Russo,Ph.D.,Scientist
Expert Committee:(PA1)Pharmaceutical Analysis 1
Pharmacopeial Forum:Volume No.29(5)Page 1586
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