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Zileuton
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C11H12N2O2S 236.29
Urea, N-(1-benzo[b]thien-2-ylethyl)-N-hydroxy-, (±)-.
(±)-1-(1-Benzo[b]thien-2-ylethyl)-1-hydroxyurea [111406-87-2].
» Zileuton contains not less than 98.5 percent and not more than 101.5 percent of C11H12N2O2S, calculated on the anhydrous basis.
Packaging and storage— Preserve in tight, light-resistant containers, and store at room temperature.
Identification—
B: The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay.
Specific rotation 781S: between –0.5 and +0.5.
Test solution: 10 mg per mL, in methanol.
Water, Method I 921: not more than 1.5%.
Residue on ignition 281: not more than 0.2%.
Specific surface area, Method I 846 Outgas a portion of the test sample, about 100 mg, at 90 for 1 hour at ambient pressure using 0.001 mole fraction of krypton in helium as the adsorbate gas: between 0.9 and 3.1. m2 per g.
Arsenic, Method II 211: 2 µg per g.
Limit of boron—
Sulfuric acid solution— Carefully add 50 mL of sulfuric acid to 450 mL of water, and mix.
Standard solution— Prepare a solution in Sulfuric acid solution having a concentration of about 2.0 µg of boron per mL. Use of a commercially prepared boron ICP standard solution is recommended.
Test solution— Accurately weigh approximately 1.0 g of Zileuton into a 125-mL conical flask. Add 1 to 1.5 mL of sulfuric acid, and digest in a fume hood on a hot plate until charring begins. Add 2 mL of nitric acid to the cooled sample to aid digestion, and heat until brown fumes are not evolved. Cautiously add 30 percent hydrogen peroxide, dropwise, allowing the reaction to subside, and heating between drops. Add the first few drops very slowly with sufficient mixing in order to prevent a rapid reaction. Discontinue heating if foaming becomes excessive. When the reaction has abated, heat cautiously, rotating the flask occasionally to prevent the sample from caking on glass exposed to the heating unit. Maintain oxidizing conditions at all times during the digestion by adding small quantities of the 30 percent hydrogen peroxide, whenever the mixture turns brown or darkens. Approximately 1 to 2 mL of nitric acid can be added, if necessary, which will create a refluxing effect to wash down any particles adhering to the neck of the flask. Continue the digestion until the organic matter is destroyed, gradually raising the temperature of the hot plate until fumes of sulfur trioxide are copiously evolved and the solution becomes colorless or retains only a light straw color. Transfer the solution to a 25-mL volumetric flask using about 7 mL of water. Repeat the washing twice more, and combine the washings in the volumetric flask. Dilute with water to volume, and mix.
Procedure— The inductively coupled plasma-atomic emission spectrometer is set up with wavelength of 249.7 nm, RF power of 1.25 KW, argon torch flow of about 13 L per minute, argon nebulizer flow of about 1 L per minute, and argon auxillary flow of about 0.5 L per minute. Analyze the Standard solution and the Test solution, using Sulfuric acid solution as the blank. Calculate the quantity, in µg of boron per g, in the portion of Zileuton taken by the formula:
25C/W,
where C is the concentration, in µg per mL, of boron in the Test solution determined from the instrument; and W is the weight, in g, of the Zileuton: not more than 10 µg per g is found.
Limit of pyridine—
Standard solution— Dissolve an accurately weighed quantity of pyridine, approximately 250 mg, in dimethyl sulfoxide, and dilute with dimethyl sulfoxide to 50 mL. Transfer 5 µL to a 100-mL sealed headspace vial.
Test solution, Chromatographic system, and Procedure— Proceed as directed for Test Solution, Chromatographic System, and Procedure under Organic Volatile Impurities, Method IV 467. Separately inject the Standard solution and the Test solution into the gas chromatograph, and record the peak responses. Calculate the quantity, in ppm, of pyridine in the portion of Zileuton taken by the formula:
100(rU / rS)(WS / WU),
in which rU and rS are the peak responses for pyridine in the Test solution and the Standard solution, respectively; WS is the weight, in mg, of pyridine used to prepare the Standard solution; and WU is the weight, in mg, of Zileuton: not more than 100 ppm is found.
Chromatographic purity— [NOTE—For Test 1 and Test 2, the System suitability solution, the Standard solution, and the Test solution are to be refrigerated at or below 5 immediately after preparation and during analysis using a refrigerated autosampler. The solutions are stable at or below 5 for about 36 hours.]
TEST 1—
Buffer solution— Prepare as directed in the Assay.
Mobile phase— Prepare a filtered and degassed mixture of Buffer solution and acetonitrile (82:18). Make adjustments if necessary (see System Suitability under Chromatography 621).
System suitability solution— Dissolve accurately weighed quantities of USP Zileuton RS and USP Zileuton Related Compound A RS in acetonitrile, and dilute quantitatively, and stepwise if necessary, to obtain a solution having a known concentration of about 5 µg of each USP Reference Standard per mL.
Standard solution— Dissolve an accurately weighed quantity of USP Zileuton RS in acetonitrile to obtain a solution having a known concentration of about 10 µg per mL.
Test solution— Transfer about 125 mg of Zileuton, accurately weighed, to a 50-mL volumetric flask, dissolve in and dilute with acetonitrile to volume, and mix.
Chromatographic system— Prepare as directed in the Assay, except to use a flow rate of 2.2 mL per minute. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the resolution, R, between zileuton and zileuton related compound A is not less than 1.5; and the relative standard deviation for replicate injections is not more than 5.0%.
Procedure— Separately inject equal volumes (about 20 µL) of the Standard solution and the Test solution into the chromatograph, and measure the areas for the major peaks. Calculate the percentage of each impurity in the portion of Zileuton taken by the formula:
100F(CS / CU)(ri / rS),
in which F is the relative response factor for each impurity, which is 1.0 for any peak with a relative retention time of 0.5, 0.7, 1.2, 1.6, 3.2, or 3.4, and is 1.2, 1.4, and 1.7 for peaks with relative retention times of 0.8, 2.1, and 2.8, respectively; CS is the concentration, in mg per mL, of USP Zileuton RS in the Standard solution; CU is the concentration, in mg per mL, of zileuton in the Test solution; ri is the peak response for each impurity obtained from the Test solution; and rS is the peak response for zileuton obtained from the Standard solution: not more than 0.1% of any individual impurity with a relative retention time of 0.8, 1.6, or 2.1 is found; not more than 0.10% of any individual impurity with a relative retention time of 0.7, 3.2, or 3.4 is found; not more than 0.20% of any individual impurity with a relative retention time of 0.5 or 1.2 is found; and not more than 0.07% of any individual impurity with a relative retention time of 2.8 is found.
TEST 2—
Perchloric acid solution— Dissolve 5.0 mL of perchloric acid in 1000 mL of water.
Mobile phase— Prepare a filtered and degassed mixture of Perchloric acid solution and acetonitrile (1:1). Make adjustments if necessary (see System Suitability under Chromatography 621).
Standard stock solution— Dissolve an accurately weighed quantity of USP Zileuton Related Compound B RS in acetonitrile to obtain a solution having a known concentration of about 0.25 mg per mL. Transfer 5.0 mL of this solution to a 50-mL volumetric flask, dilute with acetonitrile to volume, and mix.
System suitability solution— Dissolve an accurately weighed quantity of USP Zileuton Related Compound C RS in acetonitrile to obtain a solution having a known concentration of about 10 µg per mL. Transfer 5.0 mL of this solution and 5.0 mL of the Standard stock solution to a 50-mL volumetric flask, dilute with acetonitrile to volume, and mix.
Standard solution— Transfer 5.0 mL of the Standard stock solution to a 50-mL volumetric flask, dilute with acetonitrile to volume, and mix.
Test solution— Proceed as directed for Test solution under Test 1.
Chromatographic system— Prepare as directed in the Assay. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the resolution, R, between zileuton related compound B and zileuton related compound C is not less than 20. Chromatograph the Standard solution, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 5.0%.
Procedure— Separately inject equal volumes (about 50 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the areas for the major peaks. Calculate the percentage of each impurity in the portion of Zileuton taken by the formula:
100(CS / CU)(ri / rS),
in which CS is the concentration, in mg per mL, of USP Zileuton Related Compound B RS in the Standard solution; CU is the concentration, in mg per mL, of zileuton in the Test solution; ri is the peak response for each impurity obtained from the Test solution; and rS is the peak response for zileuton related compound B obtained from the Standard solution: not more than 0.1% of any individual impurity is found; and not more than 0.7% of total impurities is found, the results for Test 1 and Test 2 being added.
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Assay—
NOTE—The Standard preparation and the Assay preparation are to be refrigerated at or below 5 immediately after preparation and during analysis using a refrigerated autosampler. The solutions are stable at or below 5 for about 36 hours.
Buffer solution— Dissolve 7.7 g of ammonium acetate and 0.25 g of acetohydroxamic acid in about 900 mL of water in a 1000-mL volumetric flask, adjust with perchloric acid to a pH of 2.0, dilute with water to volume, and mix.
Mobile phase— Prepare a filtered and degassed mixture of Buffer solution and acetonitrile (72:28). Make adjustments if necessary (see System Suitability under Chromatography 621).
Internal standard preparation— Transfer about 30 mg of methylparaben, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with acetonitrile to volume, and mix.
Standard stock preparation— Dissolve an accurately weighed quantity of USP Zileuton RS in acetonitrile to obtain a solution having a known concentration of about 1 mg per mL.
Standard preparation— Transfer 5.0 mL of the Standard stock preparation and 4.0 mL of the Internal standard preparation to a 50-mL volumetric flask, dilute with acetonitrile to volume, and mix.
Assay preparation— Transfer about 100 mg of Zileuton, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with acetonitrile to volume, and mix. Transfer 5.0 mL of this solution and 4.0 mL of the Internal standard preparation to a 50-mL volumetric flask, dilute with acetonitrile to volume, and mix.
Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 260-nm detector and a 4.6-mm × 30-cm column that contains 10-µm packing L1. The flow rate is about 1.5 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the resolution, R, between zileuton and methylparaben is not less than 5.0; the tailing factor is not more than 1.3; and the relative standard deviation for replicate injections is not more than 0.6%.
Procedure— Separately inject equal volumes (about 20 µL) of the Assay preparation and the Standard preparation into the chromatograph, record the chromatograms, and measure the peak areas. Calculate the quantity, in mg, of C11H12N2O2S in the portion of Zileuton taken by the formula:
1000C(RU / RS),
in which C is the concentration, in mg per mL, of USP Zileuton RS in the Standard preparation; and RU and RS are the peak area ratios obtained from the Assay preparation and the Standard preparation, respectively.
Auxiliary Information— Staff Liaison : Daniel K. Bempong, Ph.D., Scientist
Expert Committee : (MDPS05) Monograph Development-Pulmonary and Steroids
USP29–NF24 Page 2285
Pharmacopeial Forum : Volume No. 30(3) Page 948
Phone Number : 1-301-816-8143