Assay—
[NOTE—Use low-actinic glassware.
]Transfer an accurately measured volume of Oral Solution,or a quantitative dilution of it in water,equivalent to about 10mg of promazine hydrochloride,to a 250-mLseparator.Add water to adjust the volume to about 45mL,add 3mLof sodium hydroxide solution (1in 10),mix,and extract the promazine with five 25-mLportions of ether.Wash the combined ether extracts with 25mLof water,and discard the aqueous washings.Extract the combined ether extract with one 50-mLand four 25-mLportions of 0.1Nhydrochloric acid.Filter the acid extracts through a pledget of cotton washed with 0.1Nhydrochloric acid into a 250-mLvolumetric flask,dilute with the same acid to volume,and mix.Without delay,concomitantly determine the absorbances of this solution and of a Standard solution of
USP Promazine Hydrochloride RSin the same medium having a known concentration of about 40µg per mLin 1-cm cells at the wavelength of maximum absorbance at about 301nm,with a suitable spectrophotometer,using 0.1Nhydrochloric acid as the blank.Calculate the quantity,in mg,of C
17H
20N
2S·HCl in each mLof the Oral Solution taken by the formula:
(0.25C/V)(AU/AS),
in which
Cis the concentration,in µg per mL,of
USP Promazine Hydrochloride RSin the Standard solution,
Vis the volume,in mL,of Oral Solution taken,and
AUand
ASare the absorbances from the assay solution and the Standard solution,respectively.