Iron 241:
not more than 5 ppm.
Standard iron solution
Use the
Standard Iron Solution prepared as directed under
Iron 241.
Hydroxylamine solution
Dissolve 5 g of hydroxylamine hydrochloride in 50 mL of water.
Triazine solution
Dissolve 125 mg of 2,4,6-tri-(2-pyridyl)-S-triazine in 100 mL of methanol.
Standard solution
Into a 50-mL color-comparison tube pipet 1 mL of Standard iron solution, add 42.0 mL of water, and mix.
Test solution
Into a 50-mL color-comparison tube add 2.0 g of Dipivefrin Hydrochloride, 43.0 mL of water, and mix.
Procedure
To each of the tubes containing the Standard solution and the Test solution, add 5.0 mL of Hydroxylamine solution, 2.0 mL of Triazine solution, and mix: the color of the solution from the Test solution is not darker than that of the solution from the Standard solution.
Assay
Mobile phase
Prepare a mixture of acetonitrile, 0.014 M sodium dodecyl sulfate, and glacial acetic acid (24:15:1).
Standard preparation
Dissolve a suitable quantity of
USP Dipivefrin Hydrochloride RS, accurately weighed, in 0.0015 N hydrochloric acid to obtain a solution having a known concentration of about 5 mg per mL.
Assay preparation
Prepare as directed for Standard preparation, using 500 mg of Dipivefrin Hydrochloride, accurately weighed, in place of the Reference Standard.
Chromatographic system (see Chromatography 621)
The liquid chromatograph is equipped with a 254-nm detector and a 4-mm × 30-cm column that contains packing L1. The flow rate is about 2 mL per minute. Chromatograph the
Standard preparation, and record the peak responses as directed for
Procedure: the column efficiency is not less than 500 theoretical plates; the tailing factor for the major peak is not more than 1.5; and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure
Separately inject equal volumes (about 20 µL) of the
Standard preparation and the
Assay preparation into the chromatograph by means of a suitable microsyringe or sampling valve, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C
19H
29NO
5·HCl in the portion of Dipivefrin Hydrochloride taken by the formula:
100C(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Dipivefrin Hydrochloride RS in the
Standard preparation; and
rU and
rS are the peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.