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» Cycloserine has a potency of not less than 900 µg of C3H6N2O2 per mg.
Packaging and storage Preserve in tight containers.
USP Reference standards 11
Identification Dissolve about 1 mg in 10 mL of 0.1 N sodium hydroxide. To 1 mL of the resulting solution add 3 mL of 1 N acetic acid and 1 mL of a mixture, prepared 1 hour before use, of equal parts of sodium nitroprusside solution (1 in 25) and 4 N sodium hydroxide: a blue color gradually develops.
Condensation products Its absorptivity (see Spectrophotometry and Light-Scattering 851) at 285 nm, determined in a 0.1 N sodium hydroxide solution containing 0.40 mg per mL is not more than 0.80.
Specific rotation 781S: between 108 and 114.
Test solution: 50 mg per mL, in 2 N sodium hydroxide.
Crystallinity 695: meets the requirements.
pH 791: between 5.5 and 6.5, in a solution (1 in 10).
Loss on drying 731 Dry about 100 mg in a capillary-stoppered bottle in vacuum at 60 for 3 hours: it loses not more than 1.0% of its weight.
Residue on ignition 281: not more than 0.5%, the charred residue being moistened with 2 mL of nitric acid and 5 drops of sulfuric acid.
pH 6.8 Phosphate buffer Prepare as directed in Buffer Solutions under Solutions in the section Reagents, Indicators, and Solutions.
Mobile phase Dissolve 0.5 g of sodium 1-decanesulfonate in 800 mL of water, add 50 mL of acetonitrile and 5 mL of glacial acetic acid, and mix. Adjust with 1 N sodium hydroxide to a pH of 4.4. Filter, and degas. Make adjustments if necessary (see System Suitability under Chromatography 621).
Standard preparation Quantitatively dissolve an accurately weighed quantity of USP Cycloserine RS in pH 6.8 Phosphate buffer to obtain a solution having a known concentration of about 0.4 mg per mL.
Assay preparation Transfer about 20 mg of Cycloserine, accurately weighed, to a 50-mL volumetric flask, dissolve in and dilute with pH 6.8 Phosphate buffer to volume, and mix.
Chromatographic system (see Chromatography 621) The liquid chromatograph is equipped with a 219-nm detector and a 4.6-mm × 25-cm column that contains 5-µm packing L1. The flow rate is about 1 mL per minute. The column temperature is maintained at about 30. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the tailing factor is not more than 1.8; 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 peak responses for cycloserine. Calculate the quantity, in µg, of C3H6N2O2 in each mg of Cycloserine taken by the formula:
50,000(C/W)(rU / rS)in which C is the concentration, in mg per mL, of USP Cycloserine RS in the Standard preparation; W is the quantity, in mg, of Cycloserine taken to prepare the Assay preparation; and rU and rS are the peak responses for cycloserine obtained from the Assay preparation and the Standard preparation, respectively.
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USP35NF30 Page 2792Pharmacopeial Forum: Volume No. 27(5) Page 2998