สารบัญ

Thai name น้ำมันสะระแหน่ญวน (NAMMAN SARANAE YUAN)

Category   Pharmaceutic aid (flavouring agent).

             Spearmint Oil is obtained by steam distillation from the fresh, overground parts of the flowering plants of Mentha spicata L. and Mentha × cardiaca (Gray) Bak. (Family Lamiaceae). 

Constituents  Spearmint Oil contains predominantly carvone.  It also contains limonene, pulegole, cineole, etc.

Description  Clear colourless, pale yellow, or greenish yellow liquid when recently distilled, but becoming darker and viscous on keeping; odour, that of spearmint.

Labelling  The label on the container states whether the oil is American-type oil or Chinese-type oil.

Identification  The retention time of the principal peaks in the chromatogram of the Spearmint Oil correspond to those in the chromatogram of the Standard solution, as obtained in the Chromatographic profile.

Packaging and storage  Spearmint Oil shall be kept in well-filled, tightly closed containers, protected from light, and at a temperature below 25º.

Weight per millilitre  American-type oil 0.917 to 0.934; Chinese-type oil 0.935 to 0.952 (Appendix 4.9).

Optical rotation  American-type oil −45º to −60 º; Chinese-type oil −50º to −62º (Appendix 4.8).

Refractive index  1.484 to 1.491, at 20º (Appendix 4.7).

Solubility test  Soluble, at 20°, in 1 volume of ethanol (80 per cent); the solution may become cloudy when diluted.

Chromatographic profile  Carry out the test as described in the “Gas Chromatography” (Appendix 3.4).
      Standard solution  Mix carefully 0.1 g of limonene, 0.2 g of 1,8-cineole, 0.4 g of menthone, 0.1 g of (+)-isomenthone, 0.4 g of menthyl acetate, 0.2 g of pulegone, 0.6 g of menthol, and 0.1 g of carvone with 1 g of  hexane.
      Test solution  Use Spearmint Oil.
      Chromatographic system
          DETECTOR  Flame ionization
          COLUMN  A glass capillary column (25 m to 60 m × 0.25 mm) packed with macrogol 20000 (0.25 µm) (Carbowax 20M^® or equivalent is suitable).
          TEMPERATURE
                Column The temperature programme is as follows:

                    Injection port 220°
                    Detector 230°
             CARRIER GAS  Helium
                    Flow rate  1.5 mL per minute.
              System suitability
                    Sample  Standard solution.
              Suitability requirements
                    COLUMN EFFICIENCY  Not less than 30,000 theoretical plates for the limonene peak in the chromatogram of the standard solution.
                    RESOLUTION  Not less than 1.5 between limonene and cineole peaks.
               Procedure  Inject a portion (about 0.1 mL) of Standard solution and Spearmint Oil into the chromatograph.  Identify the peaks due to the components in Spearmint Oil, using the retention times determined from the chromatogram obtained from the standard solution.  Measure the areas of the principal peaks in the chromatogram obtained from the Spearmint Oil.
               Calculation  Calculate the percentage content of the components of Spearmint Oil taken by normalization procedure. 
               Limits
               —  limonene:  2.0 per cent to 25 per cent,
               —  cineole:  not more than 2.5 per cent,
               —  menthone:  not more than 2.5 per cent,
               —  isomenthone:  not more than 1.0 per cent,
               —  menthyl acetate:  not more than 1.0 per cent,
               —  pulegone:  not more than 0.5 per cent,
               —  menthol:  not more than 2 per cent,
               —  carvone:  not less than 55 per cent.