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Expressed Almond Oil, Sweet Almond Oil.

Category Emollient and vehicle for oily injections.

Almond Oil is the fixed oil obtained by cold expression from the kernels of varieties of Prunus dulcis (Miller) D.A. Webb (formerly known as P. amygdalus Batsch) (Family Rosaceae), except for P. dulcis (Miller) D.A. Webb var. amara (de Candolle) Focke.

Origin of plant Almond oil-yielding plant is native to Mediterranean Region.

Constituents Almond Oil contains fatty acids predominantly oleic, linoleic, and palmitic acids. It also contains sterols (β-sitosterol, ∆5-avenasterol, campesterol, and stigmasterol), triacylglycerols (OLO, OLLn, OOO, etc., where O is oleic acid, L is linoleic acid, and Ln is linolenic acid), and tocopherols (alpha-tocopherol and γ- tocopherol).

Description A pale yellow oil; odour, slight and characteristic; taste, bland.

Solubility Practically insoluble in ethanol; miscible with chloroform, with ether, and with petroleum ether (boiling range 40º to 60º).

Packaging and storage Almond Oil shall be kept in well-filled, tightly closed containers, protected from light, and stored at a temperature not exceeding 25.

Identification of fixed oils by thin-layer chromatography Carry out the test as described in Appendix==.

Results The chromatogram obtained is similar to the corresponding chromatogram shown in the figure.

Composition of fatty acids Carry out the test as described in the “Gas Chromatography” (Appendix 3.4).

Standard solution Prepare an ester mixture of known composition containing the esters required in the Almond oil. (Nu-Chek mixture 17A® or equivalent is suitable.)

0.5 M Methanolic sodium hydroxide solution

Dissolve 2 g of sodium hydroxide in 100 mL of methanol.

Test solution (Note If fatty acids containing more than 2 double bonds are present in the sample, remove air from the flask by purging it with nitrogen for a few minutes.) Transfer about 100 mg of the sample, accurately weighed, to a 50-mL conical flask fitted with a suitable water-cooled reflux condenser and a magnetic stir bar. Add 4 mL of 0.5 M Methanolic sodium hydroxide solution, and reflux until fat globules disappear (usually 5 to 10 minutes). Add 5.0 mL of a solution prepared by dissolving 14 g of boron trifluoride in methanol to make 100 mL, swirl to mix, and reflux for 2 minutes. Add 4 mL of n-heptane for chromatography through the condenser, and reflux for 1 minute. Cool, remove the condenser, add about 15 mL of a saturated solution of sodium chloride, shake, and allow the layers to separate. Pass the nheptane layer through 100 mg of anhydrous sodium sulfate (previously washed with n-heptane for chromatography) into a suitable flask. Transfer 1.0 mL of this solution to a 10-mL volumetric flask, dilute with n-heptane for chromatography to volume, and mix.

System suitability solution Transfer about 20 mg each of stearic acid, palmitic acid, and oleic acid to a 25-mL conical flask fitted with a suitable water-cooled reflux condenser and a magnetic stir bar, and prepare as directed for Test solution beginning with “Add 5.0 mL of a solution prepared by dissolving . . . .”

Chromatographic system

DETECTOR Flame ionization.

COLUMN A fused-silica capillary column (30 m × 0.53 mm) bonded with a 1.0-µm layer of polyethylene glycol compound (Polyethylene Glycol Compound 20M®, also known as Carbowax 20M®, or equivalent.)

TEMPERATURE

Column The temperature programme is as follows:

Injection port 220°.

Detector 260°.

CARRIER GAS Helium.

FLOW RATE About 50 cm per second (6.6 mL per minute).

(Note The relative retention times are about 0.87, 0.99, and 1.0 for methyl palmitate, methyl stearate, and methyl oleate, respectively.)

System suitability

SAMPLE System suitability solution.

Suitability requirements

RESOLUTION Not less than 1.5 between methyl stearate and methyl oleate peaks.

RELATIVE STANDARD DEVIATION The relative standard deviation of the peak area responses for the palmitate and stearate peaks for replicate injections is not more than 6.0 per cent. The relative standard deviation of the peak area response ratio of the palmitate to stearate peaks from these replicate injections is not more than 1.0 per cent.

Procedure Separately inject equal volumes (about 1 µL) of Standard solution and Test solution into the chromatograph, and record the chromatograms. Identify the peak due to the fatty acid ester peaks in the chromatogram of the Test solution by comparing the retention times of these peaks with those in the chromatogram of the Standard solution, and measure the peak areas for all of the fatty acid ester peaks in the chromatogram from the Test solution.

Calculation Calculate the percentage content of the components of Almond Oil taken by normalization procedure.

Limits Almond Oil exhibits the composition profiles of fatty acids in Table 1 below.

Table 1

Acid value Not more than 0.5 (Appendix 5.4).

Peroxide value Not more than 5.0 (Appendix 5.12).

Unsaponifiable matter Not more than 0.9 per cent w/w (Appendix 5.8).

Specific gravity 0.910 to 0.915 (Appendix 4.9).