Lemon Oil
» Lemon Oil is the volatile oil obtained by expression, without the aid of heat, from the fresh peel of the fruit of Citrus x limon (L.) Osbeck (Fam. Rutaceae), with or without the previous separation of the pulp and the peel. The total aldehyde content, calculated as citral (C10H16O), is not less than 2.2 percent and not more than 3.8 percent for California-type Lemon Oil, and not less than 3.0 percent and not more than 5.5 percent for Italian-type Lemon Oil.
note—Do not use Lemon Oil that has a terebinthine odor.
Packaging and storage— Preserve in well-filled, tight containers, and avoid exposure to excessive heat.
Labeling— The label states the Latin binomial and, following the official name, the part of the plant source from which the article was derived. Label it to also indicate whether it is California-type or Italian-type Lemon Oil. The label indicates that Oil is not to be used if it has a terebinthine odor.
Specific gravity 841: between 0.849 and 0.855.
Angular rotation 781A: between +57 and +65.6.
Refractive index 831: between 1.473 and 1.476 at 20.
Ultraviolet absorbance— Transfer about 250 mg of Oil, accurately weighed, to a 100-mL volumetric flask, add alcohol to volume, and mix. Record the UV absorption spectrum of this solution from 260 to 400 nm in a 1-cm cell, using alcohol as the blank. Determine the absorbance at the wavelength of maximum absorbance at about 315 nm using the line drawn tangent to the curves appearing as minima in the spectrum in wavelength regions above and below the maximum wavelength as the baseline. The absorbance, calculated on the basis of a 250-mg specimen, is not less than 0.20 for California-type Lemon Oil, or not less than 0.49 for Italian-type Lemon Oil.
Foreign oils— Place 50 mL of Oil in a four-bulb Ladenburg flask having the following dimensions: the lower or main bulb is about 6 cm in diameter, and the smaller condensing bulbs are about 3.5, 3.0, and 2.5 cm in diameter; the distance from the bottom of the flask to the side-arm is about 20 cm. Distill Oil at a rate of 1 drop per second until the distillate measures 5 mL: the angular rotation of the first 5 mL is not more than 6 less than that of the original Oil. The refractive index at 20 of this same portion is between 0.001 and 0.003 lower than that of the original Oil.
Assay— Dissolve 4.5 g of hydroxylamine hydrochloride in 13 mL of water, add 85 mL of tertiary butyl alcohol, mix, and adjust with 0.5 N potassium hydroxide to a pH of 3.4. Pipet 50 mL of this solution into a conical flask containing about 5 mL of Oil, accurately weighed. Insert the stopper in the flask, and allow to stand at room temperature for 30 minutes, with occasional shaking. Titrate the liberated hydrochloric acid with 0.5 N alcoholic potassium hydroxide VS to a pH of 3.4. Each mL of 0.5 N alcoholic potassium hydroxide consumed in the titration is equivalent to 76.12 mg, of total aldehydes, calculated as citral (C10H16O).
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Monograph Rick G. Schnatz
Manager, Compounding Pharmacy Expert Committee
(CRX05) Compounding Pharmacy05
USP32–NF27 Page 1267
Pharmacopeial Forum: Volume No. 27(4) Page 2798