» Benzocaine, dried over phosphorus pentoxide for 3 hours, contains not less than 98.0 percent and not more than 102.0 percent of C9H11NO2.
Packaging and storage Preserve in well-closed containers.
A: Infrared Absorption 197K: previously dried over phosphorus pentoxide for 3 hours.
B: Ultraviolet Absorption 197U
Solution: 5 µg per mL.
Absorptivities at 278 nm, calculated on the dried basis, do not differ by more than 3.0%.
C: Dissolve about 20 mg in 10 mL of water with the aid of a few drops of 3 N hydrochloric acid, and add 5 drops of a solution of sodium nitrite (1 in 10), followed by 2 mL of a solution of 100 mg of 2-naphthol in 5 mL of 1 N sodium hydroxide: an orange-red precipitate is formed.
Melting range, Class I 741: between 88 and 92, but the range between beginning and end of melting does not exceed 2.
Reaction Dissolve 1.0 g in 10 mL of neutralized alcohol: a clear solution results. Dilute this solution with 10 mL of water, and add 2 drops of phenolphthalein TS and 1 drop of 0.10 N sodium hydroxide: a red color is produced.
Loss on drying 731 Dry it over phosphorus pentoxide for 3 hours: it loses not more than 1.0% of its weight.
Readily carbonizable substances 271 Dissolve 500 mg in 5 mL of sulfuric acid TS: the solution has no more color than Matching Fluid A.
Residue on ignition 281: not more than 0.1%.
Chloride To a solution of 200 mg in 5 mL of alcohol, previously acidified with a few drops of diluted nitric acid, add a few drops of silver nitrate TS: no turbidity is produced immediately.
Heavy metals, Method II 231: 0.001%.
Ordinary impurities 466
Test solution: dehydrated alcohol.
Standard solution: dehydrated alcohol.
Application volume: 10 µL.
Eluant: chloroform containing about 0.75% of dehydrated alcohol as a preservative, in a nonequilibrated chamber.
Limit The total of any ordinary impurities observed does not exceed 1%.
Aqueous solution To 980 mL of water, add 20 mL of acetic acid and 1 mL of triethylamine, and mix well. The pH should be between 2.95 and 3.0; adjust as needed.
Mobile phase Prepare a filtered and degassed mixture of Aqueous solution and methanol (60:40).
Standard preparation Dissolve an accurately weighed quantity of USP Benzocaine RS in Mobile phase, and dilute quantitatively, and stepwise if necessary, with Mobile phase to obtain a solution having a known concentration of about 0.024 mg per mL.
Assay preparation Transfer about 24 mg of Benzocaine, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with Mobile phase to volume, and mix. Dilute 10 mL of this solution with Mobile phase to 100 mL.
Chromatographic system (see Chromatography 621) The liquid chromatograph is equipped with a 285-nm detector and a 2.0-mm × 15-cm column that contains 5-µm packing L11. The flow rate is about 0.2 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the tailing factor of the benzocaine peak is not more than 2.0; and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure Separately inject equal volumes (about 10 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the benzocaine peaks. Calculate the quantity, in mg, of C9H11NO2 in the portion of Benzocaine taken by the formula:
1000C(rU / rS)in which C is the concentration, in mg per mL, of USP Benzocaine RS in the Standard preparation; rU and rS are the peak responses obtained from the Assay preparation and Standard preparation, respectively; and 1000 is the dilution factor for the Assay preparation.
Auxiliary Information Please check for your question in the FAQs before contacting USP.Chromatographic Column
USP32NF27 Page 1640Pharmacopeial Forum: Volume No. 34(5) Page 1147
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.