A: Infrared Absorption á197Kñ.

B: Ultraviolet Absorption á197Uñ—

Solution: 10µg per mL.

Medium: pH4.5buffer solution [prepared by dissolving 13.61g of monobasic potassium phosphate in 750mLof water,adjusting to a pHof 4.5±0.1with potassium hydroxide solution (1in 180)and diluting with water to 1000mL].Absorptivities at 290nm,calculated on the dried basis,do not differ by more than 3.0%.

C: It meets the requirements of the tests for Chloride á191ñ.

4-Amino-2-chlorobenzoic acid— Using the chromatograms obtained as directed for the Assay,calculate the percentage of 4-amino-2-chlorobenzoic acid (C7H6ClNO2)in the Chloroprocaine Hydrochloride taken by the formula: in which Cis the concentration,in mg per mL,of 4-amino-2-chlorobenzoic acid in the Standard preparation;Wis the quantity,in mg,of Chloroprocaine Hydrochloride taken to prepare the Assay preparationand rUand rSare the 4-amino-2-chlorobenzoic acid peak responses obtained from the Assay preparationand the Standard preparation,respectively:not more than 0.625%is found.

Mobile phase— Dissolve 800mg of sodium 1-heptanesulfonate in 740mLof water,add 200mLof acetonitrile,50mLof methanol,and 10mLof glacial acetic acid,and mix.Filter and degas this solution.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard 4-amino-2-chlorobenzoic acid solution— Dissolve an accurately weighed quantity of recrystallized 4-amino-2-chlorobenzoic acid in methanol to obtain a solution having a known concentration of about 0.2mg per mL.

Standard preparation— Transfer about 50mg of USP Chloroprocaine Hydrochloride RS,accurately weighed,to a 50-mLvolumetric flask containing 5.0mLof Standard 4-amino-2-chlorobenzoic acid solution,add 15mLof methanol,swirl to dissolve,dilute with water to volume,and mix.This solution contains about 1mg of USP Chloroprocaine Hydrochloride RSand 0.02mg of 4-amino-2-chlorobenzoic acid per mL.

System suitability solution— Mix equal volumes of Standard 4-amino-2-chlorobenzoic acid solutionand Standard preparation.

Assay preparation— Transfer about 100mg of Chloroprocaine Hydrochloride,accurately weighed,to a 100-mLvolumetric flask,dissolve in 40mLof methanol,dilute with water to volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 278-nm detector and a 3.9-mm ×30-cm column containing packing L1.The flow rate is about 2mLper minute.Chromatograph the System suitability solution,and record the responses as directed for Procedure:the relative retention times are about 0.35for 4-amino-2-chlorobenzoic acid and 1.0for chloroprocaine;and the resolution,R,between 4-amino-2-chlorobenzoic acid and chloroprocaine is not less than 5.0.Chromatograph the Standard preparation,and record the responses as directed for Procedure:the relative standard deviation determined from chloroprocaine obtained from replicate injections is not more than 1.0%.

Procedure— Separately inject equal volumes (about 5µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the peak responses for 4-amino-2-chlorobenzoic acid and chloroprocaine.Calculate the quantity,in mg,of C13H19ClN2O2·HCl in the portion of Chloroprocaine Hydrochloride taken by the formula: in which Cis the concentration,in mg per mL,of USP Chloroprocaine Hydrochloride RSin the Standard preparation;and rUand rSare the chloroprocaine peak responses obtained from the Assay preparationand the Standard preparation,respectively.