Assay
Transfer to a suitable separator an accurately measured volume of Injection,equivalent to about 20mg of pyridostigmine bromide.Add 10mLof 1Nhydrochloric acid,and mix.Extract with four 20-mLportions and one 15-mLportion of ethyl ether,and discard the extracts.Transfer the aqueous layer to a 100-mLvolumetric flask,using about 25mLof water to aid the transfer.Place the flask on a steam bath and warm,with the aid of a stream of nitrogen,to evaporate any residual ether,then cool the flask to room temperature,dilute with water to volume,and mix.Dilute 20.0mLof the resulting solution with 0.1Nhydrochloric acid to 100.0mL,and mix.Dissolve an accurately weighed quantity of
USP Pyridostigmine Bromide RSin 0.1Nhydrochloric acid to obtain a Standard solution having a known concentration of about 40µg per mL.Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 269nm,with a suitable spectrophotometer,using 0.1Nhydrochloric acid as the blank.Calculate the quantity,in mg,of C
9H
13BrN
2O
2in each mLof the Injection taken by the formula:
(0.5C/V)(AU/AS),
in which
Cis the concentration,in µg per mL,of
USP Pyridostigmine Bromide RSin the Standard solution,
Vis the volume,in mL,of Injection taken,and
AUand
ASare the absorbances of the solution from the Injection and the Standard solution,respectively.