TEST 1
Mobile phase
Prepare a filtered and degassed mixture of dehydrated alcohol, chromatographic solvent hexane, methanol, and diethylamine (55:40:5:0.2). Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Test solution
Transfer about 25 mg of Brinzolamide, accurately weighed, to a 50-mL volumetric flask, dissolve in and dilute with dehydrated alcohol to volume, and mix.
Chromatographic system (see Chromatography 621)
The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm × 25-cm column that contains packing L51. The flow rate is about 0.75 mL per minute. Chromatograph the
System suitability solution, and record the peak responses as directed for
Procedure: the relative retention times are about 1.0 for brinzolamide and 1.2 for brinzolamide related compound A; the resolution,
R, between brinzolamide and brinzolamide related compound A is not less than 1.8; the column efficiency determined from brinzolamide is not less than 2000 theoretical plates; and the tailing factor for the brinzolamide peak is not more than 1.8.
Procedure
Inject about 5 µL of the
Test solution into the chromatograph, record the chromatogram, and measure the peak areas for brinzolamide and brinzolamide related compound A. Calculate the percentage of brinzolamide related compound A in the portion of Brinzolamide taken by the formula:
100(rU / rs),
in which
rU is the peak response for brinzolamide related compound A; and
rs is the sum of the peak responses for brinzolamide and brinzolamide related compound A: not more than 0.5% of brinzolamide related compound A is found.
TEST 2
Triethylamine phosphate buffer
Prepare as directed in the Assay.
Mobile phase 1
Prepare as directed for
Mobile phase in the
Assay. Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Mobile phase 2
Prepare a filtered and degassed mixture of Triethylamine phosphate buffer and acetonitrile (65:35).
Test solution
Transfer about 50 mg of Brinzolamide, accurately weighed, to a 50-mL volumetric flask, dissolve in and dilute with Mobile phase 1 to volume, and mix.
Chromatographic system (see Chromatography 621)
The liquid chromatograph is equipped with a 230-nm detector and a 4.6-mm × 25-cm column that contains 5-µm packing L1. The flow rate is about 1.0 mL per minute. Using
Mobile phase 1, chromatograph the
System suitability solution, and record the peak responses as directed for
Procedure: the relative retention times are about 0.8 for brinzolamide related compound B and 1.0 for brinzolamide; the resolution,
R, between brinzolamide and brinzolamide related compound B is not less than 2.0; the column efficiency determined from brinzolamide is not less than 1200 theoretical plates; and the tailing factor for the brinzolamide peak is not more than 2.0.
Procedure
Using
Mobile phase 1, separately inject equal volumes (about 10 µL) of
Mobile phase 1 and the
Test solution into the chromatograph, record the chromatograms, allowing the elution to continue for 20 minutes, and measure the areas for all the peaks, excluding the peaks obtained from
Mobile phase 1. Calculate the percentage of each impurity in the portion of Brinzolamide taken by the formula:
100(ri / rs),
in which
ri is the peak response for each impurity; and
rs is the sum of the responses for all the peaks: not more than 0.3% of any individual impurity is found.
Equilibrate the system with Mobile phase 2, inject the Test solution again, record the chromatograms, allowing the elution to continue for 20 minutes, and measure the areas for brinzolamide and all the peaks having a relative retention time greater than 6. Calculate the percentage of each impurity in the portion of Brinzolamide taken by the formula:
100(ri / rs),
in which ri is the peak response for each impurity; and rs is the sum of the responses for all the peaks: not more than 0.3% of any individual impurity is found; and not more than 1.0% of total impurities using Mobile phase 1 and Mobile phase 2 is found.