Tetradecanoic acid [544-63-8].
» Myristic Acid is obtained from coconut oil and other fats. It contains not less than 97.0 percent of C14H28O2.
Packaging and storage Preserve in well-closed containers. No storage requirements specified.
Congealing temperature 651: between 48 and 55.5.
Acid value 401: between 242 and 249.
Iodine value 401: not more than 1.0.
Saponification value 401: between 242 and 251.
Unsaponifiable matter 401: not more than 1%.
Water, Method I 921: not more than 0.2%.
Residue on ignition 281: not more than 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 about 160 mg of lead nitrate, accurately weighed, in 100 mL of water containing 1 mL of nitric acid. Dilute with water to 1000 mL, and mix.
Standard solutions [notePrepare these solutions on the day of use.] Transfer 10.0 mL of Standard stock solution to a 100-mL volumetric flask, dilute with water to volume, and mix. 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 about 1 µg, 2 µg, and 5 µg of lead per mL.
Test solution Transfer about 5 g of Myristic Acid, accurately weighed, 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 approximately 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, dilute with water to volume, and mix.
Procedure Using a suitable atomic absorption spectrophotometer (see Spectrophotometry and Light-Scattering 851) equipped with a lead electrodeless discharge lamp, an airacetylene flame, and a suitable burner head, perform a blank determination with water, following the manufacturer's operating instructions. Concomitantly determine the absorbances of the blank, the Standard solutions, and the Test solution at the lead emission line of 283.3 nm, using a slit-width of 0.7 nm. 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 Test solution. Prepare a standard curve by plotting the corrected absorbance values of the Standard solutions versus their corresponding concentration, in µg per mL. From the calibration curve, determine the lead concentration in the Test solution. Calculate the lead content, in µg per g, in the portion of Myristic Acid taken by the formula:
10C/WSin which C is the concentration, in µg per mL, of lead from the standard curve; and WS is the weight, in g, of Myristic Acid taken: not more than 2 µg per g is found.
Resolution solution Proceed as directed for the System Suitability Solution in Fatty Acid Composition under Fats and Fixed Oils 401, except that only stearic acid and palmitic acid are used.
Standard preparation Prepare as directed for the Assay preparation using 100 mg of USP Myristic Acid RS instead of the substance to be examined.
Assay preparation Proceed as directed for the Test Solution in Fatty Acid Composition under Fats and Fixed Oils 401.
Chromatographic system (see Chromatography 621) Prepare as directed for Fatty Acid Composition under Fats and Fixed Oils 401. Chromatograph the Resolution solution, and record the peak responses as directed for Procedure: the resolution, R, between methyl stearate and methyl palmitate is not less than 1.5.
Procedure Separately inject equal volumes (about 1 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and identify the methyl myristate peak in the chromatogram obtained from the Assay preparation by comparing the retention times of the peaks in that chromatogram with those in the chromatogram obtained from the Standard preparation. Measure the responses for all of the peaks in the chromatogram obtained from the Assay preparation, excluding the solvent peak, and calculate the percentage of C14H28O2 in the portion of Myristic Acid taken by the formula:
100A/B,in which A is the the methyl myristate peak response; and B is the sum of the responses of all the peaks in the chromatogram, except the solvent peak.
Auxiliary Information Please check for your question in the FAQs before contacting USP.Chromatographic Column
USP32NF27 Page 1285Pharmacopeial Forum: Volume No. 30(5) Page 1666
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.