U.S. PHARMACOPEIA

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Cocoa Butter
»Cocoa Butter is the fat obtained from the seed of Theobroma cacao Linné (Fam. Sterculiaceae).
Packaging and storage— Preserve in well-closed containers.
Melting range— Melt the material to be tested at a temperature between 50 and 60. Place about 50 g of the melted material in a beaker, and cool in a water bath at 25. Stir continuously until it assumes a pasty consistency, taking care to avoid the inclusion of air bubbles. Place the beaker in a water bath maintained at a temperature between 32 and 33. Continue stirring until the specimen reaches the temperature of the water bath and changes to a liquid cream (about 30 minutes). Pour the contents into another beaker, and allow it to solidify at room temperature for at least 2 hours. Press one side of a U-shaped capillary tube, 1.5 mm in diameter and about 80 mm in length with a distance of about 10 mm between both capillaries, into the solidified specimen. Using a very fine metal rod, push the column down to 10 mm before the bend of the U-tube. Then attach the other arm of the U-tube to a precision thermometer (having 0.1 graduations) by suitable means, with the U-tube bend at the level of the thermometer bulb. Insert the thermometer into a water bath so that the upper edge of the material is at least 20 mm below the surface, and heat as directed for Class I under Melting Range or Temperature 741 except, within 5 of the expected melting temperature, to regulate the rate of the temperature rise so that it does not exceed 0.2 per minute. The slip point (temperature at which the column visibly flows towards the bend in the tube) is between 30 and 34. The clear melting point (clarity via magnifying glass) is between 31 and 35.
Free fatty acids 401— The free fatty acids in 10.0 g of it require for neutralization not more than 5.0 mL of 0.10 N sodium hydroxide (1.4% as oleic acid).
Refractive index 831: between 1.454 and 1.459 at 40.
Fatty acid composition—
Test solution— Place about 100 to 150 mg of Cocoa Butter in a 50-mL round-bottom flask, and add 4 mL of 0.5 N sodium hydroxide solution, prepared in methanol. Add a few boiling chips to the flask, connect the round-bottom flask to a condenser, and boil the mixture under total reflux until the fat globules go into solution. Add 5.0 mL of a 2.0 M borontrifluoride in methanol solution to the boiling mixture via the condenser, and continue boiling for 2 minutes. Add 2 to 5 mL of chromatographic n-heptane to the boiling mixture via the condenser, and boil for another minute. Remove the flask from the source of heat, and remove the reflux condenser. Add saturated sodium chloride solution, and swirl the flask gently. Add more of the saturated sodium chloride solution to bring the liquid level into the neck of the round-bottom flask. Transfer about 1 mL of the organic layer into a glass-stoppered test tube, add some anhydrous sodium sulfate to remove the last traces of water, and filter. Use the filtrate.
System suitability solution— Dissolve suitable quantities of methyl stearate and methyl oleate in n-heptane to obtain a solution having a known concentration of about 1 mg per mL for each component.
Chromatographic system (see Chromatography 621)— The gas chromatograph is equipped with a flame-ionization detector maintained at a temperature of about 250, a 0.25-mm × 15-m fused-silica capillary column coated with 0.25-µm stationary phase G19, and a split injection system with a split ratio of about 60:1, maintained at a temperature of about 250. The carrier gas is helium flowing at a linear velocity of about 48 cm per second. The column temperature is programmed to increase linearly from 180 to 240 at a rate of 10 per minute, and is maintained at 240 for 5 minutes. [NOTE—The components of interest elute during the temperature program. The final hold at a temperature of 240 serves only to facilitate elution of higher boiling components.] Inject about 0.1 µL of the System suitability solution into the chromatograph, record the chromatogram, and measure the responses for the major peaks: the relative retention times are about 0.97 for stearate and 1.0 for oleate; the resolution, R, between the stearate and oleate peaks is not less than 1.5; and the relative standard deviation for replicate injections is not more than 5.0%.
Procedure— Inject about 0.1 µL of the Test solution into the chromatograph, record the chromatogram, and measure the areas for the peaks of the methyl esters of the fatty acids. [NOTE—The relative retention times for palmitate, stearate, oleate, linoleate, linolenate (if present), and arachidate are about 1.0, 1.55, 1.60, 1.72, 1.89, and 2.30, respectively.] Calculate the percentage of each fatty acid methyl ester in the specimen of Cocoa Butter taken by the formula:
100(ri / rs),
in which ri is the response of each peak; and rs is the sum of the responses of all of the peaks: the percentages of palmitate, stearate, oleate, linoleate, linolenate (if present), and arachidate are in the ranges of 23 to 30, 31 to 37, 31 to 38, 1.6 to 4.8, 0 to 1.5, and 0 to 1.5, respectively.
Iodine value 401: between 33 and 42.
Saponification value 401: between 188 and 198.
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Auxiliary Information— Staff Liaison : Hong Wang, Ph.D. , Senior Scientific Associate
Expert Committee : (EM205) Excipient Monographs 2
USP29–NF24 Page 3315
Pharmacopeial Forum : Volume No. 30(1) Page 207
Phone Number : 1-301-816-8351