Identification—
To 5mLof Syrup in a separator add 100mLof 2.5Nhydrochloric acid,and mix.Extract with five 20-mLportions of chloroform,place 2mLof the aqueous solution in a 50-mLvolumetric flask,and add water to volume:the UVabsorption spectrum of this solution exhibits maxima and minima at the same wavelengths as that of a similar solution of
USP Pyridostigmine Bromide RS,concomitantly measured.
Assay—
Phosphate solution—
Dissolve 38g of monobasic sodium phosphate and 2g of anhydrous dibasic sodium phosphate in water to make 1000mL.Adjust the pH,if necessary,by slight variation of the ratio of the two ingredients,to 5.3±0.1.
Bromocresol green solution—
Dissolve 250mg of bromocresol green sodium salt in 250mLof Phosphate solution.
Standard preparation—
Dissolve a suitable quantity of
USP Pyridostigmine Bromide RS,accurately weighed,in water,to obtain a solution having a known concentration of about 1.2mg per mL.
Assay preparation—
Transfer an accurately measured volume of Syrup,equivalent to about 120mg of pyridostigmine bromide,to a 100-mLvolumetric flask,add water to volume,and mix.
Procedure—
Transfer 10mLeach,accurately measured,of the
Assay preparationand the
Standard preparationto separate 125-mLseparators.Into each separator pipet 10mLof water,20mLof
Phosphate solution,and 5mLof
Bromocresol green solution.Extract each solution with six 15-mLportions of chloroform,collecting the chloroform extracts in respective 100-mLvolumetric flasks,then add chloroform to volume in each flask,and mix.Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 415nm,with a suitable spectrophotometer,using chloroform as the blank.Calculate the quantity,in mg,of C
9H
13BrN
2O
2in the portion of Syrup taken by the formula:
100C(AU/AS),
in which
Cis the concentration,in mg per mL,of
USP Pyridostigmine Bromide RSin the
Standard preparation;and
AUand
ASare the absorbances of the solutions from the
Assay preparationand the
Standard preparation,respectively.