A: The UVabsorption spectrum of the Assay preparation,prepared as directed in the Assay,exhibits maxima and minima at the same wavelengths as that of the Standard preparation,prepared as directed in the Assay,concomitantly measured.

B: Place a volume of Injection,equivalent to about 30mg of dibucaine hydrochloride,in a suitable evaporating dish,and concentrate on a steam bath to a volume of about 10mL.Transfer the solution to a separator,render distinctly alkaline with 1Nsodium hydroxide,and extract with four 20-mLportions of ether.Wash the combined ether extracts with 5mLof water,discarding the washing.Evaporate the ether extracts with the aid of a current of air to dryness,and dry the residue over phosphorus pentoxide for 3hours:the dibucaine so obtained melts between 62and 65.

Mobile phase and Chromatographic system— Proceed as directed in the Assayunder Dibucaine.

Standard preparation— Transfer about 50mg of USP Dibucaine Hydrochloride RS,accurately weighed,to a 100-mLvolumetric flask,add an accurately measured volume of water,equivalent to the volume of Injection taken to prepare the Assay preparation,dilute with methanol to volume,and mix.Where the Assay preparationis prepared in a 50-mLvolumetric flask,transfer about 25mg of USP Dibucaine Hydrochloride RS,accurately weighed,to a 100-mLvolumetric flask,add an accurately measured volume of water,equivalent to twice the volume of Injection taken to prepare the Assay preparation,dilute with methanol to volume,and mix.Filter through a suitable filter of 0.5-µm or finer porosity.

Assay preparation— Transfer an accurately measured volume of Injection,equivalent to about 50mg of dibucaine,to a 100-mLvolumetric flask.Dilute with methanol to volume,and mix.Where the Injection is labeled to contain 1mg or less of dibucaine hydrochloride per mL,transfer an accurately measured volume of Injection,equivalent to about 13mg of dibucaine hydrochloride,to a 50-mLvolumetric flask,dilute with methanol to volume,and mix.Filter through a suitable filter of 0.5-µm or finer porosity.

Procedure— Separately inject equal volumes (about 10µL,or 20µLwhere the concentration of dibucaine hydrochloride is about 0.25mg per mL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the area responses for the major peaks.Calculate the quantity,in mg,of dibucaine hydrochloride (C20H29N3O2·HCl)in each mLof the Injection taken by the formula: in which Cis the concentration,in mg per mL,of USP Dibucaine Hydrochloride RSin the Standard preparation;vis the volume,in mL,of the Assay preparation;Vis the volume,in mL,of Injection taken;and rUand rSare the area responses of the dibucaine peaks obtained from the Assay preparationand the Standard preparation,respectively.