(mi ris' tik as' id).
Tetradecanoic acid [544-63-8].
Myristic Acid is obtained from coconut oil and other fats. It contains NLT 97.0% of myristic acid (C14H28O2).
• Fats and Fixed Oils, Fatty Acid Composition 401
System suitability solution: Prepare as directed in the chapter, except that only stearic acid and palmitic acid are used.
Sample solution: Prepare as directed in the chapter for the Test solution.
Standard solution: Prepare as directed for the Sample solution using 100 mg of USP Myristic Acid RS instead of the substance to be examined.
Chromatographic system: Prepare as directed in the chapter.
Injection size: 1 µL
Sample: System suitability solution
Resolution: NLT 1.5 between methyl stearate and methyl palmitate
Samples: Standard solution and Sample solution
Record the chromatograms, and identify the methyl myristate peak in the chromatogram from the Sample solution by comparing the retention times of the peaks in that chromatogram with those in the chromatogram from the Standard solution. Measure the responses for all of the peaks in the chromatogram from the Sample solution, excluding the solvent peak.
Calculate the percentage of myristic acid (C14H28O2) in the portion of Myristic Acid taken:
Result = (A/B) × 100
Acceptance criteria: NLT 97.0%
• Residue on Ignition 281: NMT 0.1%
• Limit of Lead
[NoteSelect reagents having as low a lead content as practicable, and store all solutions in high-density polyethylene containers. Rinse all plastic and glassware thoroughly with warm 8 N nitric acid followed by deionized water. ]
Standard stock solution: Dissolve 160 mg of lead nitrate in 100 mL of water containing 1 mL of nitric acid. Dilute with water to 1000 mL.
Standard solutions: [NotePrepare these solutions on the day of use. ] Transfer 10.0 mL of Standard stock solution to a 100-mL volumetric flask, and dilute with water to volume. Each mL of this solution contains the equivalent of about 10 µg of lead. Dilute accurately measured volumes of the diluted Standard stock solution with water to obtain solutions having known concentrations of 1, 2, and 5 µg of lead/mL.
Sample solution: Transfer 5 g of Myristic Acid to an evaporating dish. Add 5 mL of a 25% sulfuric acid solution, and distribute the sulfuric acid uniformly through the sample. Within a hood, place the dish on a steam bath to evaporate most of the water. Place the dish on a burner, and slowly pre-ash the sample by expelling most of the sulfuric acid. Place the dish in a muffle furnace that has been set at 525, and ash the sample until the residue appears free from carbon. Prepare a blank by ashing 5 mL of a 25% sulfuric acid solution. Cool, and cautiously wash down the inside of each evaporation dish with water. Treat both the sample and the blank as follows. Add 5 mL of 1 N hydrochloric acid. Place each dish on a steam bath, and evaporate to dryness. To each dish add 1.0 mL of 3 N hydrochloric acid and about 5 mL of water, and heat briefly on a steam bath to dissolve any residue. Transfer each solution quantitatively to a 10-mL volumetric flask, and dilute with water to volume.
Mode: Atomic absorption spectrophotometry
Analytical wavelength: 283.3 nm at the lead emission line
Slit-width: 0.7 nm
Lamp: Lead electrodeless discharge
Flame: Airacetylene with a suitable burner head
Blank: Water. [NotePerform a blank determination following the manufacturer's operating instructions. ]
Samples: Standard solutions, Sample solution, and Blank
Determine the corrected absorbance values by subtracting the absorbance of the Blank from the absorbance of each of the Standard solutions and from the absorbance of the Sample solution. Prepare a standard curve by plotting the corrected absorbance values of the Standard solutions versus their corresponding concentration, in µg/mL. From the calibration curve, determine the lead concentration in the Sample solution.
Calculate the lead content, in ppm, in the portion of Myristic Acid taken:
Result = (C/WS) × V
Acceptance criteria: NMT 2 ppm
• Congealing Temperature 651: 4855.5
• Fats and Fixed Oils, Acid Value 401: 242249
• Fats and Fixed Oils, Iodine Value 401: NMT 1.0
• Water Determination, Method I 921: NMT 0.2%
• Packaging and Storage: Preserve in well-closed containers. No storage requirements specified.
• USP Reference Standards 11
USP Myristic Acid RS
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USP35NF30 Page 1873Pharmacopeial Forum: Volume No. 30(5) Page 1666