Packaging and storage—
Preserve in tight, single-dose
Containers for Injections as described under
Injections 
1
, preferably of Type I glass. Store in a refrigerator or at controlled room temperature.
Identification—
A:
Thin-Layer Chromatographic Identification Test 201—
Test solution—
Pipet 1.0 mL of Injection into a 10-mL volumetric flask. Dilute with methanol to volume, and mix.
Standard solution:
1 mg per mL in methanol.
Application volume:
20 µL.
Developing solvent system—
Prepare a homogeneous mixture of acetone, chloroform, acetic acid, and water (6:2:1:1). Place mixture in a paper-lined chromatographic chamber, and equilibrate for about 15 minutes prior to use.
Procedure—
Proceed as directed in the chapter, and then dry the plate under a current of warm air until completely dry. Place the plate into a second chromatographic chamber containing iodine crystals, and examine the plate: meets the requirements.
B:
The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay.
Related compounds—
Diluent, Mobile phase, System suitability solution, Standard preparation, Column treatment, and Chromatographic system—
Proceed as directed in the Assay.
Test preparation—
Use the Assay preparation.
Procedure—
Separately inject equal volumes (about 10 µL) of the
Standard preparation and the
Test preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg per mL, of fenoldopam related compound B (C
16H
16NO
3·CH
4SO
3) in the volume of Injection taken by the formula:
WS S(DS / DU)(rU / rS),
in which
WS is the weight, in mg, of
USP Fenoldopam Related Compound B RS taken;
S is the conversion factor from the fenoldopam related compound B to the free base (i.e., 0.77026);
DS and
DU are the dilution factors for the
Standard preparation and the
Test preparation, respectively (i.e., 0.0001 and 0.02); and
rU and
rS are the average peak responses for fenoldopam related compound B obtained from the
Test preparation and the
Standard preparation, respectively: not more than 0.6% is found.
Content of sodium metabisulfite—
Transfer 10.0 mL of Injection to a glass-stoppered conical flask containing 5.0 mL of 0.1 N iodine VS, and swirl to dissolve. Allow to stand for exactly 5 minutes, protected from light. Add 0.5 mL of hydrochloric acid, and titrate the excess iodine with 0.05 N sodium thiosulfate VS, adding 0.5 mL of
starch TS as the endpoint is approached. Perform a blank determination, and make any necessary correction. Each mL of 0.05 N sodium thiosulfate is equivalent to 2.3763 mg of sodium metabisulfite: not less than 0.25 mg per mL of Injection is found.
Assay—
Diluent—
Dissolve about 1.38 g of monobasic sodium phosphate monohydrate in 1 L of water, adjust with a phosphoric acid solution (1 in 9) to a pH of 2.5, and mix.
Mobile phase—
Dissolve about 1.38 g of monobasic sodium phosphate monohydrate and 1.88 g of sodium hexanesulfonate in 1 L of water, adjust with a phosphoric acid solution (1 in 9) to a pH of 2.5, and mix. Prepare a filtered and degassed mixture of this solution and methanol (67:33). Make adjustments if necessary (see
System Suitability under
Chromatography 621).
System suitability solution—
Transfer about 2.74 mg of
USP Fenoldopam Related Compound B RS, accurately weighed, to a 100-mL volumetric flask. Dissolve in and dilute with
Diluent to volume, and mix.
Standard preparation—
Transfer about 26.3 mg of
USP Fenoldopam Mesylate RS, accurately weighed, to a 100-mL volumetric flask, and dissolve in about 75 mL of
Diluent. Add, by pipetting, 1.0 mL of the
System suitability solution, dilute with
Diluent to volume, and mix.
Assay preparation—
Accurately pipet about 0.5 mL of Injection into a 25-mL volumetric flask, dilute with Diluent to volume, and mix.
Column treatment—
[NOTE—This treatment is required for new columns only.] Pump a solution of cyclam (1 in 1000) through the new column for about 3 hours at a flow rate of about 1 mL per minute, and then pump Mobile phase for at least 2 hours at the same flow rate.
Chromatographic system (see Chromatography 621)—
The liquid chromatograph is equipped with a 225-nm detector and a 4.6-mm × 25-cm column that contains packing L1. The flow rate is about 1.0 mL per minute. Chromatograph the
System suitability solution, and record the peak responses as directed for
Procedure: the capacity factor,
k¢, is between 1 and 3; the column efficiency is not less than 1800 theoretical plates; and the tailing factor is not more than 2.5. Chromatograph the
Standard preparation, and record the peak responses as directed for
Procedure: the capacity factor,
k¢, is between 4 and 6; the column efficiency is not less than 1800 theoretical plates; the tailing factor 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 major peaks. Calculate the quantity, in mg per mL, of fenoldopam mesylate (C
16H
16ClNO
3·CH
4SO
3) in the volume of Injection taken by the formula:
WSS(DS / DU)(rU / rS),
in which
WS is the weight, in mg, of
USP Fenoldopam Mesylate RS taken;
S is the conversion factor from the fenoldopam mesylate to the free base (i.e., 0.7610);
DS and
DU are the dilution factors for the
Standard preparation and the
Assay preparation, respectively (i.e., 0.01 and 0.02); and
rU and
rS are the fenoldopam peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
