U.S. PHARMACOPEIA

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Tetracaine
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C15H24N2O2 264.36

Benzoic acid, 4-(butylamino)-, 2-(dimethylamino)ethyl ester.
2-(Dimethylamino)ethyl p-(butylamino)benzoate [94-24-6].
» Tetracaine contains not less than 98.0 percent and not more than 101.0 percent of C15H24N2O2, calculated on the dried basis.
Packaging and storage— Preserve in tight, light-resistant containers.
Identification—
A: Dissolve 100 mg in 10 mL of dilute hydrochloric acid (1 in 120), and add 1 mL of potassium thiocyanate solution (1 in 4): a crystalline precipitate is formed. Recrystallize the precipitate from water, and dry at 80 for 2 hours: it melts between 130 and 132 (see Melting Range or Temperature 741).
B: Dissolve about 90 mg, accurately weighed, in 10 mL of dilute hydrochloric acid (1 in 120) in a 500-mL volumetric flask, dilute with water to volume, and mix. Transfer 5.0 mL of this solution to a 100-mL volumetric flask, add 2 mL of Buffer No. 6, 10 percent, pH 6.0 (see Phosphate Buffers 81), dilute with water to volume, and mix: the UV absorption spectrum of the solution so obtained exhibits maxima and minima at the same wavelengths as that of a 1 in 100,000 solution of USP Tetracaine Hydrochloride RS in a mixture of water and Buffer No. 6 (50:1), 10 percent, pH 6.0 (see Phosphate Buffers 81), and the respective molar absorptivities, calculated on the dried basis, at the wavelength of maximum absorbance at about 310 nm do not differ by more than 2.0%. [NOTE—The molecular weight of tetracaine hydrochloride (C15H24N2O2·HCl) is 300.82.]
Melting range, Class I 741: between 41 and 46.
Loss on drying 731— Dry it in vacuum over phosphorus pentoxide for 18 hours: it loses not more than 0.5% of its weight.
Residue on ignition 281: not more than 0.1%.
Chromatographic purity— Dissolve an accurately weighed quantity of Tetracaine in chloroform to obtain a test solution containing 50 mg per mL. Prepare a Standard solution of 4-(butylamino) benzoic acid in methanol containing 0.2 mg per mL. Apply separate 5-µL portions of the test solution and the Standard solution to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel mixture. Develop the plate in a suitable chromatographic chamber containing a solvent system consisting of a mixture of chloroform, methanol, and isopropylamine (98:7:2) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the chamber, and dry in a current of warm air. Examine the plate under short-wavelength UV light: any spot obtained from the test solution, other than the principal spot, is not more intense than the principal spot obtained from the Standard solution (0.4%), and the sum of the intensities of any such spots is not greater than 0.8%.
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Assay— Transfer about 500 mg of Tetracaine, accurately weighed, to a suitable vessel. Add 5 mL of hydrochloric acid and 50 mL of water, cool to 15, add about 25 g of crushed ice, and slowly titrate with 0.1 M sodium nitrite VS, stirring vigorously, until a glass rod dipped into the titrated solution produces an immediate blue ring when touched to starch iodide paper. When the titration is complete, the endpoint is reproducible after the mixture has been allowed to stand for 1 minute. Perform a blank determination, and make any necessary correction. Each mL of 0.1 M sodium nitrite is equivalent to 26.44 mg of C15H24N2O2.
Auxiliary Information— Staff Liaison : Daniel K. Bempong, Ph.D., Scientist
Expert Committee : (MDPS05) Monograph Development-Pulmonary and Steroids
USP29–NF24 Page 2091
Phone Number : 1-301-816-8143