Acetohydroxamic Acid Tablets
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
1 DEFINITION
Acetohydroxamic Acid Tablets contain NLT 90.0% and NMT 110.0% of the labeled amount of acetohydroxamic acid (C2H5NO2).
2 IDENTIFICATION
A. Tablets produce a purple color when mixed with an acidic solution of ferric chloride.
2.1 ASSAY
Procedure
Ferric chloride solution: 20 mg/mL of ferric chloride in 0.1 N hydrochloric acid
Standard solution: 500 μg/mL of USP Acetohydroxamic Acid RS in 0.1 N hydrochloric acid
Sample solution: Weigh, and nely powder NLT 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 500 mg of acetohydroxamic acid, to a 1000-mL volumetric flask, add about 500 mL of 0.1 N hydrochloric acid, and shake for 1 min. Dilute with 0.1 N hydrochloric acid to volume, and mix. Filter, discarding the rst 40 mL of the filtrate. Use the clear filtrate.
Blank: 0.1 N hydrochloric acid
Analysis
Samples: Standard solutions, Sample solution, and Blank
Transfer 10.0 mL each of the Standard solution, Sample solution, and Blank to separate 100-mL volumetric flasks. To each flask add 50mL of 0.1 N hydrochloric acid and 10.0 mL of Ferric chloride solution, and dilute with 0.1 N hydrochloric acid to volume. Without delay, concomitantly determine the absorbances of the solutions at the wavelength of maximum absorbance at about 502 nm, using the Blank to set the instrument.
Calculate the percentage of labeled amount of acetohydroxamic acid (C2H5NO2) in the portion of Tablets taken:
Result = (Au/As) × (Cs/Cu) × 100
Au = absorbance of the Sample solution
As = absorbance of the Standard solution
Cs = concentration of USP Acetohydroxamic Acid RS in the Standard solution (μg/mL)
Cu = nominal concentration of acetohydroxamic acid in the Sample solution (μg/mL)
Acceptance criteria: 90.0%–110.0%
3 PERFORMANCE TESTS
Dissolution, Procedure for a Pooled Sample〈711〉
Medium: 0.01 N hydrochloric acid; 900 mL
Apparatus 1: 100 rpm
Time: 30 min
Analysis: Calculate the percentage of the labeled amount of acetohydroxamic acid (C H NO ) dissolved, using the procedure in the Assay,using a filtered portion of the solution under test as Sample solution in comparison with a Standard solution having a known concentration of USP Acetohydroxamic Acid RS in Medium.
Tolerances: NLT 85% (Q) of the labeled amount of acetohydroxamic acid (C H NO ) is dissolved.
Uniformity of Dosage Units 〈905〉: Meet the requirements
4 IMPURITIES
Limit of Hydroxylamine
Buffer: 1.36 g/L of monobasic potassium phosphate in water, adjusted with 1 M potassium hydroxide to a pH of 7.4
Solution A: 1 mg/mL of pyridoxal 5-phosphate monohydrate in Buffer, prepared in a low-actinic flask fresh before use
Standard stock solution: 2.0 mg/mL of hydroxylamine hydrochloride in water
Standard solutions: Transfer 5.0, 10.0, and 15.0 mL of the Standard stock solution to separate 100-mL volumetric flasks, and dilute with water to volume.
Sample solution: Weigh, and finely powder NLT 20 Tablets. Transfer a portion of the powder, equivalent to about 1500 mg of acetohydroxamic acid to a 50-mL stoppered centrifuge tube. Add 30.0 mL of water, shake for about 2 min, and centrifuge. Pipet 15.0 mL of the clear solution into a 50-mL beaker, add just enough water to cover the electrode of a calibrated pH meter, and while stirring, adjust with 0.5 M potassium hydroxide to a pH of 7.4. Quantitatively transfer the contents of the beaker with the aid of small portions of water to a 50-mL volumetric flask, dilute with water to volume, and mix.
Blank: Water
Analysis
Samples: Standard solutions, Sample solution, and Blank
Transfer 2.0 mL of each Standard solution, the Sample solution, and Blank into separate 100-mL volumetric flasks. To each flask add 4.0mL of Solution A. After 8 min, accurately timed, dilute the contents of each flask with Buffer to volume.
Immediately determine the fluorescence intensities of the solutions from the Standard solutions and the Sample solution in a fluorometer at an excitation wavelength of 350 nm and an emission wavelength of 450 nm, setting the instrument to zero with the Blank. Determine the best-fit straight line from the fluorescence intensities of the three Standard solutions versus the hydroxylamine hydrochlorideconcentrations, in μg/mL. From the best-fit straight line, determine the concentration, in μg/mL, of hydroxylamine hydrochloride in the
Sample solution.
Calculate the percentage of hydroxylamine in the portion of Tablets taken:
Result = (Cu/C) × (Mr1/Mr2) × 100
Cu= concentration of hydroxylamine hydrochloride in the Sample solution (μg/mL)
C = nominal concentration of acetohydroxamic acid in the Sample solution (μg/mL)
Mr1 = molecular weight of hydroxylamine, 33.03
Mr2 = molecular weight of hydroxylamine hydrochloride, 69.50
Acceptance criteria: NMT 0.5%
5 ADDITIONAL REQUIREMENTS
Packaging and Storage: Preserve in tight containers.
USP Reference Standards 〈11〉
USP Acetohydroxamic Acid RS
