Standard solution— Transfer 2.0 mL of 0.100 N iodine VS to a 500-mL volumetric flask, dilute with water to volume, and mix.

Procedure— Visually examine a portion of the Injection (Test solution) in a suitable clear glass test tube against a white background: it is not pinkish and it contains no precipitate. If any yellow color is observed in the Test solution, concomitantly determine the absorbances of the Test solution and the Standard solution in 1-cm cells with a suitable spectrophotometer set at 460 nm: the absorbance of the Test solution does not exceed that of the Standard solution.

A: Extract a volume of Injection, equivalent to about 200 mg of mepivacaine, with two 10-mL portions of ether, and discard the ether extracts. Render slightly alkaline with sodium carbonate TS, extract the precipitate with ether, evaporate the ether extract on a steam bath to dryness, and dry the residue in vacuum at 60 for 1 hour: the mepivacaine so obtained melts between 149 and 153.

B: It meets the requirements of the tests for Chloride 191.

Ferro-citrate Solution and Buffer Solution— Prepare as directed under Epinephrine Assay 391.

Standard preparation— With the aid of 20 mL of sodium bisulfite solution (1 in 50), transfer about 25 mg of USP Levonordefrin RS, accurately weighed, to a 50-mL volumetric flask, dilute with water to volume, and mix. Transfer 5 mL of this solution to a 50-mL volumetric flask, dilute with sodium bisulfite solution (1 in 500) to volume, and mix to obtain a solution having a known concentration of about 50 µg per mL. [note—Make the final dilution at the time the assay is to be carried out.]

Assay preparation— Use the Injection, diluting, if necessary, to obtain a concentration of about 50 µg of levonordefrin per mL.

Procedure— Proceed as directed under Epinephrine Assay 391, except to read levonordefrin wherever epinephrine (base) is called for. When the Ferro-citrate Solution and the Buffer Solution are mixed with the Assay preparation, a fine precipitate may be formed. Remove this precipitate by centrifugation or by passing through dry filter paper before the colorimetric measurements are taken. Calculate the quantity, in mg, of levonordefrin (C9H13NO3) in each mL of the Injection taken by the formula: in which C is the concentration, in mg per mL, of USP Levonordefrin RS in the Standard preparation; VF is the final volume of the Assay preparation after dilution; VT is the volume of Injection taken to prepare the Assay preparation; and AU and AS are the absorbances of the Assay preparation and the Standard preparation, respectively. [note—When dilution of the Injection is not necessary, VF / VT is equal to 1.]