A: It responds to the Identificationtest under Physostigmine.

B: It responds to the tests for Salicylate á191ñ.

0.05M Ammonium acetate— Dissolve 3.85g of ammonium acetate in 1liter of water,and adjust,if necessary,with glacial acetic acid or ammonium hydroxide to a pHof 6±0.1.

Mobile phase— Prepare a filtered and degassed mixture of equal volumes of acetonitrile and 0.05M Ammonium acetate.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Benzyl alcohol-benzaldehyde solution— Prepare a mixture of 100µLof benzyl alcohol and 1µLof benzaldehyde in each 400mLof acetonitrile.

Standard preparation— Dissolve an accurately weighed quantity of USP Physostigmine Salicylate RSin Benzyl alcohol-benzaldehyde solution,and dilute quantitatively,and stepwise if necessary,with Benzyl alcohol-benzaldehyde solution,to obtain a solution having a known concentration of about 30µg per mL.

Assay preparation— Transfer an accurately measured volume of Injection,equivalent to about 3mg of physostigmine salicylate,to a 100-mLvolumetric flask,dilute with acetonitrile to volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm ×30-cm column that contains packing L1.The flow rate is about 2mLper minute.Separately chromatograph 10-µLportions of the Benzyl alcohol-benzaldehyde solutionand the Standard preparation,and record the peak responses as directed under Procedure [NOTE—If the components of the Benzyl alcohol-benzaldehyde solution co-elute,the Standard preparation will exhibit only 2peaks instead of 3.]:in a suitable system,benzyl alcohol and benzaldehyde elute before physostigmine,the column efficiency determined from the analyte peak is not less than 1200theoretical plates,the resolution,R,between physostigmine and the adjacent peak (benzyl alcohol or benzaldehyde or the combination of these)is not less than 2.0,and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C15H21N3O2·C7H6O3in each mLof the Injection taken by the formula: in which Cis the concentration,in µg per mL,of USP Physostigmine Salicylate RSin the Standard preparation,Vis the volume,in mL,of Injection taken,and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.