(nal i dix' ik as' id).
1,8-Naphthyridine-3-carboxylic acid, 1-ethyl-1,4-dihydro-7-methyl-4-oxo-.
1-Ethyl-1,4-dihydro-7-methyl-4-oxo-1,8-naphthyridine-3-carboxylic acid [389-08-2].
» Nalidixic Acid contains not less than 99.0 percent and not more than 101.0 percent of C12H12N2O3, calculated on the dried basis.
Packaging and storage Preserve in tight containers.
USP Reference standards 11
B: Ultraviolet Absorption 197U
Solution: 5 µg per mL.
Medium: 0.01 N sodium hydroxide.
Absorptivities at 258 nm, calculated on the dried basis, do not differ by more than 3.0%.
Melting range 741: between 225 and 231.
Loss on drying 731 Dry it at 105 for 2 hours: it loses not more than 0.5% of its weight.
Residue on ignition 281: not more than 0.1%.
Heavy metals, Method II 231: 0.002%.
Standard solutions Prepare a solution of USP Nalidixic Acid RS in chloroform containing 1.0 mg per mL. Dilute quantitatively with chloroform to obtain Standard solutions having the following composition:
Test solution Dissolve an accurately weighed quantity of Nalidixic Acid in chloroform to obtain a solution containing 20 mg per mL.
Procedure Apply separately 10 µL of the Test solution and 10 µL of each Standard solution to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel mixture. Position the plate in a chromatographic chamber, and develop the chromatograms in a solvent system consisting of a mixture of alcohol, chloroform, and 5 M ammonium hydroxide (70:20:10) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing chamber, mark the solvent front, and allow the solvent to evaporate with the aid of warm circulating air. Examine the plate under short-wavelength UV light. Compare the intensities of any secondary spots observed in the chromatogram of the Test solution with those of the principal spots in the chromatograms of the Standard solutions: no secondary spot is more intense than the principal spot obtained from Standard solution A (0.5%), and the sum of the intensities of all secondary spots obtained from the Test solution does not exceed 1.0%.
Assay Dissolve about 250 mg of Nalidixic Acid, accurately weighed, in 30 mL of dimethylformamide that previously has been neutralized to thymolphthalein TS, and titrate with 0.1 N lithium methoxide VS in methanol, using a magnetic stirrer and taking precautions against absorption of atmospheric carbon dioxide. Each mL of 0.1 N lithium methoxide is equivalent to 23.22 mg of C12H12N2O3.
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USP35NF30 Page 3984Pharmacopeial Forum: Volume No. 30(1) Page 132