Identification—
A:
Cool a mixture of 10 mL of Injection and 10 mL of 3 N hydrochloric acid in an ice bath to 0
, add 5 mL of sodium nitrite solution (1 in 5), stirring gently, and 2 mL of a solution of 0.1 g of 2-naphthol in 5 mL of 1 N sodium hydroxide, and observe immediately: a bright orange-red precipitate is formed (
presence of a primary aminophenyl group).
B:
It responds to the tests for
Chloride 
191
.
C:
To about 5 mL of Injection add 1 drop of
ferric chloride TS: a green color develops (
presence of norepinephrine bitartrate).
Assay for propoxycaine and procaine hydrochlorides—
Standard propoxycaine hydrochloride preparation—
Prepare, by quantitative and stepwise dilution, a solution in 2 N hydrochloric acid containing about 50 µg of
USP Propoxycaine Hydrochloride RS, accurately weighed, in each mL.
Standard procaine hydrochloride preparation—
Prepare, by quantitative and stepwise dilution, a solution in 2 N hydrochloric acid containing about 200 µg of
USP Procaine Hydrochloride RS, accurately weighed, in each mL.
Assay preparation—
Transfer an accurately measured volume of Injection, equivalent to about 100 mg of procaine hydrochloride, to a 125-mL separator containing 25 mL of chloroform and 10 mL of water. Add 5 mL of
sodium carbonate TS, shake vigorously, allow the layers to separate, and transfer the chloroform layer to a second separator. Extract the aqueous layer with two 10-mL portions of chloroform, adding the extracts to the second separator. Extract the combined chloroform extracts with 35 mL of 2 N hydrochloric acid, transfer the chloroform to a third separator, and transfer the acid extract to a 100-mL volumetric flask. Extract the chloroform with two 10-mL portions of 2 N hydrochloric acid, add the acid extracts to the volumetric flask, dilute with 2 N hydrochloric acid to volume, and mix. Transfer 15.0 mL of this solution to a second 100-mL volumetric flask, dilute with 2 N hydrochloric acid to volume, and mix.
Procedure—
Concomitantly determine the absorbances of the Standard preparations and the Assay preparation, in 1-cm cells, at 296 nm and 272 nm, with a suitable spectrophotometer, using water as the blank.
Calculate the quantity, in mg, of propoxycaine hydrochloride (C16H26N2O3·HCl) in each mL of the Injection taken by the formula:
(0.667
C / V)(
A296A4 
A272A3)
/ (
A1A4 A2A3),
in which
C is the concentration, in µg per mL, of
USP Propoxycaine Hydrochloride RS in the
Standard propoxycaine hydrochloride preparation,
V is the volume, in mL, of Injection taken,
A1 and
A2 are the absorbances of the
Standard propoxycaine hydrochloride preparation at 296 nm and 272 nm, respectively,
A3 and
A4 are the absorbances of the
Standard procaine hydrochloride preparation at 296 nm and 272 nm, respectively, and
A296 and
A272 are the absorbances of the
Assay preparation at 296 nm and 272 nm, respectively.
Calculate the quantity, in mg, of procaine hydrochloride (C13H20N2O2·HCl) in each mL of the Injection taken by the formula:
(0.667
C / V)(
A272A1 A296A2)
/ (
A1A4 A2A3),
in which
C is the concentration, in µg per mL, of
USP Procaine Hydrochloride RS in the
Standard procaine hydrochloride preparation, and
V is the volume, in mL, of Injection taken.
Assay for norepinephrine—
Assay preparation—
Prepare as directed for
Assay Preparation under
Epinephrine Assay 391 except to read “norepinephrine” where “epinephrine” is specified.
Procedure—
Proceed as directed for
Procedure under
Epinephrine Assay 391. Calculate the quantity, in mg, of norepinephrine (C
8H
11NO
3) in each mL of the Injection taken by the formula:
(169.18 / 319.27)(0.05C/V)(AU / AS),
in which 169.18 and 319.27 are the molecular weights of norepinephrine and norepinephrine bitartrate, respectively,
C is the concentration, in µg per mL, calculated on the anhydrous basis, of
USP Norepinephrine Bitartrate RS in the
Standard preparation, and
V is the volume, in mL, of Injection taken.
