Magnesium Oxide MgO CAS 1309-48-4 Pharmaceutical Grade 96.0%-100.5% (After Ignition)

Magnesium Oxide
MgO 40.30
Magnesium Oxide [1309-48-4]; UNII: 3A3U0GI71G.
DEFINITION
Magnesium Oxide, after ignition, contains NLT 96.0% and NMT 100.5% of Magnesium Oxide (MgO).
IDENTIFICATION
• A. IDENTIFICATION TESTS-GENERAL, Magnesium<191>: A solution in diluted hydrochloric acid meets the requirements.
ASSAY
• PROCEDURE
Diluted ammonium hydroxide: Dilute 67 g of ammonium hydroxide (about 75 mL) with water to 100 mL.
Buffer: Prepare ammonium chloride buffer pH 10 as follows. In a 100-mL volumetric ask, dissolve 5.4 g of ammonium chloride in 20 mL of water, add 35 mL of Diluted ammonium hydroxide, and dilute with water to volume.
Sample stock solution: Ignite a sample of Magnesium Oxide to a constant weight in the temperature range of (800°-900°) ± 25°.
Weigh 320 mg of the ignited sample into a 100-mL volumetric ask, dissolve in 20 mL of 2 N hydrochloric acid, and dilute with water to volume.
Sample solution: Transfer 20.0 mL of the Sample stock solution to a 500-mL ask, and dilute with water to 300 mL. The Sample solution is equivalent to 64 mg of ignited Magnesium Oxide.
Analysis: To the Sample solution, add 10 mL of Buffer and 50 mg of eriochrome black T-sodium chloride indicator. Heat the sample to 40°, and titrate to a blue endpoint with 0.1 M edetate disodium VS. Perform a blank determination, and make any necessary correction to determine the volume of 0.1 M edetate disodium consumed (V ).
Calculate the volume of 0.1 M edetate disodium, Vca , in mL, consumed by calcium, which is present in the portion of Magnesium Oxide taken:
Vca = (W × Lca)/(Fca × 100)
W = amount of ignited Magnesium Oxide in the Sample solution (mg)
Lca = content of calcium as determined in the test for Limit of Calcium (%)
Fca = weight of calcium equivalent to each mL of 0.1 M edetate disodium, 4.008 mg
Calculate the percentage of Magnesium Oxide (MgO) in the portion of Magnesium Oxide taken:
Result = (Vs − Vca ) × (FMgO /W) × 100
Vs = volume of 0.1 M edetate disodium consumed by the Sample solution (mL)
Vca = volume of 0.1 M edetate disodium consumed by calcium (mL)
FMgO = weight of Magnesium Oxide equivalent to each mL of 0.1 M edetate disodium, 4.030 mg
W = amount of the ignited Magnesium Oxide in the Sample solution (mg)
Acceptance criteria: 96.0%-100.5% after ignition
IMPURITIES
• FREE ALKALI AND SOLUBLE SALTS
Sample solution: Boil 2.0 g with 100 mL of water for 5 min in a covered beaker, and lter while hot. Allow to cool, and dilute with water to 100 mL.
Analysis 1: To 50 mL of the Sample solution add methyl red TS, and titrate with 0.10 N sulfuric acid.
Acceptance criteria 1: NMT 2.0 mL of the acid is consumed.
Analysis 2: Evaporate 25 mL of the remaining Sample solution to dryness, and dry at 105° for 1 h.
Acceptance criteria 2: NMT 10 mg of residue remains (NMT 2.0%).
• ACID-INSOLUBLE SUBSTANCES
Sample: 2 g
Analysis: Mix the Sample with 75 mL of water, add hydrochloric acid in small portions with agitation until no more dissolves, and boil for 5 min. If an insoluble residue remains, lter, wash well with water until the last washing is free from chloride, and ignite.
Acceptance criteria: The weight of the ignited residue is NMT 2 mg (NMT 0.1%).
• LIMIT OF CALCIUM
[NOTE-A commercially available atomic absorption standard solution for calcium may be used where preparation of a calcium standard stock solution is described below. Concentrations of the Standard solutions and the Sample solution may be modied to t the linear or working range of the instrument.]
Dilute hydrochloric acid: Dilute 100 mL of hydrochloric acid with water to 1000 mL.
Lanthanum solution: To 58.65 g of lanthanum oxide, add 400 mL of water, and add, gradually with stirring, 250 mL of hydrochloric acid. Stir until dissolved, and dilute with water to 1000 mL.
Standard solutions: Transfer 249.7 mg of calcium carbonate, previously dried at 300° for 3 h and cooled in a desiccator for 2 h, to a 100-mL volumetric ask. Dissolve in a minimum amount of hydrochloric acid, and dilute with water to volume. Transfer 1.0, 5.0, 10.0, and 15.0 mL of this stock solution to separate 1000-mL volumetric asks, each containing 20 mL of the Lanthanum solution and 40 mL of Dilute hydrochloric acid, and dilute with water to volume. These Standard solutions contain 1.0, 5.0, 10.0, and 15.0 µg/mL of calcium, respectively.
Sample solution: Transfer 250 mg of Magnesium Oxide, freshly ignited for 1 h in the temperature range of (800°–900°) ± 25°, to a beaker. Add 30 mL of Dilute hydrochloric acid, and stir until dissolved, heating if necessary. Transfer the solution so obtained to a 200-mL volumetric ask containing 4 mL of Lanthanum solution, and dilute with water to volume.
Blank solution: Transfer 4 mL of the Lanthanum solution and 10 mL of Dilute hydrochloric acid to a 200-mL volumetric ask, and dilute with water to volume.
Instrumental conditions
(See Atomic Absorption Spectroscopy <852>.)
Mode: Atomic absorption spectrophotometry
Analytical wavelength: Calcium emission line at 422.7 nm
Lamp: Calcium hollow-cathode
Flame: Nitrous oxide–acetylene
Analysis
Samples: Standard solutions, Sample solution, and Blank solution
Using the calibration graph, determine the concentration, C, in µg/mL, of calcium in the Sample solution.
Calculate the percentage of calcium in the portion of Magnesium Oxide taken:
Result = [(V/W) × C × F] × 100
V = volume of the Sample solution (mL)
W = weight of Magnesium Oxide (mg)
C = concentration of calcium in the Sample solution (µg/mL)
F = conversion from µg/mL to mg/mL, 0.001
Acceptance criteria: NMT 1.1%
• IRON <241>
Test preparation: Boil 40 mg with 5 mL of 2 N nitric acid for 1 min. Cool, dilute with water to 50 mL, and mix. Dilute 25 mL of this
solution with water to 45 mL, and add 2 mL of hydrochloric acid.
Acceptance criteria: NMT 0.05%
SPECIFIC TESTS
• LOSS ON IGNITION <733>
Sample: 500-1000 mg
Analysis: Transfer the Sample to a tared platinum crucible, and ignite in the temperature range of (800°-900°) ± 25° to constant weight.
Acceptance criteria: NMT 10.0%
• BULK DENSITY AND TAPPED DENSITY OF POWDERS, Bulk Density, Method I<616>: Using the procedure specied in the chapter, determine the bulk density of Magnesium Oxide.
ADDITIONAL REQUIREMENTS
• PACKAGING AND STORAGE: Preserve in tight containers.
• LABELING: Label it to indicate its bulk density. The indicated density may be in the form of a range