Timolol Maleate Tablets
» Timolol Maleate Tablets contain not less than 90.0 percent and not more than 110.0 percent of the labeled amount of C13H24N4O3S·C4H4O4.
Packaging and storage— Preserve in well-closed containers.
USP Reference standards 11
USP Timolol Maleate RS
Identification— Transfer a portion of powdered Tablets, equivalent to about 30 mg of timolol maleate, to a 50-mL volumetric flask, add about 2 mL of 0.1 N hydrochloric acid, and shake gently. Add about 30 mL of methanol, agitate for 20 minutes, add methanol to volume, mix, and centrifuge. Similarly prepare a Standard solution containing 0.6 mg of USP Timolol Maleate RS per mL. Separately apply 10 µL of the test solution and 10 µL of the Standard solution to a thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel mixture. Develop the chromatogram using a solvent system consisting of a mixture of chloroform, methanol, and ammonium hydroxide (80:20:1) until the solvent front has moved about three-fourths of the length of the plate. Air-dry, and examine under short-wavelength UV light: the RF values of the principal spots obtained from the test solution correspond to those obtained from the Standard solution.
Dissolution, Procedure for a Pooled Sample 711
Medium: 0.1 N hydrochloric acid; 500 mL.
Apparatus 1: 100 rpm.
Time: 20 minutes.
Procedure— Determine the amount of timolol maleate in solution in filtered portions of the solution under test, in comparison with a Standard solution having a known concentration of USP Timolol Maleate RS in the same medium, employing the procedure set forth in the Assay, making any necessary modifications.
Tolerances— Not less than 80% (Q) of the labeled amount of timolol maleate (C13H24N4O3S·C4H4O4) is dissolved in 20 minutes.
Uniformity of dosage units 905: meet the requirements.
pH 2.8 phosphate buffer— Transfer 22.08 g of monobasic sodium phosphate to a 2-liter volumetric flask, dilute with water to volume, adjust with phosphoric acid to a pH of 2.8 ± 0.05, and filter.
Mobile phase— Prepare a suitable degassed and filtered mixture of pH 2.8 phosphate buffer and methanol (3:2).
Standard preparation— Transfer about 50 mg of USP Timolol Maleate RS, accurately weighed, to a 500-mL volumetric flask. Add 50 mL of 0.05 M monobasic sodium phosphate. Sonicate until the standard is dissolved, add 100 mL of acetonitrile, shake, dilute with water to volume, and mix.
Assay preparation— Weigh and finely powder not less than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 10 mg of timolol maleate, to a 100-mL volumetric flask, add 10 mL of 0.05 M monobasic sodium phosphate, sonicate for 5 minutes, and add 20 mL of acetonitrile. Sonicate for 5 minutes, add 20 mL of water, shake for 10 minutes, dilute with water to volume, and mix.
Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 295-nm detector and a 3.9-mm × 30-cm column that contains packing L1. The flow rate is about 1.8 mL per minute. Chromatograph five replicate injections of the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation is not more than 2.0%, and the tailing factor for the main peak is not greater than 2.0.
Procedure— Separately inject equal volumes (about 15 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 C13H24N4O3S·C4H4O4 in the portion of Tablets taken by the formula:
100C(rU / rS)
in which C is the concentration, in mg per mL, of USP Timolol Maleate RS in the Standard preparation, and rU and rS are the peak responses obtained for timolol maleate from the Assay preparation and the Standard preparation, respectively.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Sujatha Ramakrishna, Ph.D.
(MDCV05) Monograph Development-Cardiovascular
Reference Standards Lili Wang, Technical Services Scientist
711 Margareth R.C. Marques, Ph.D.
Senior Scientist
(BPC05) Biopharmaceutics05
USP32–NF27 Page 3749
Pharmacopeial Forum: Volume No. 30(1) Page 191
Chromatographic Column—
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.