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       Citronella Oil is the volatile oil obtained by distillation from the fresh aerial parts of Cymbopogon winterianus Jowitt.
Description  Pale yellow to brownish yellow liquid; odour, strong and characteristic.
Packaging and storage  Citronella Oil shall be kept in well-filled, tightly closed containers, preferably of metal or glass, protected from light, and stored at a temperature not exceeding 25°.
Identification
     A. The chromatogram of the Test solution shows several peaks, eight of which correspond to those of the Standard solution, as obtained in the Composition.
(Note Neral and geranial may be absent in the chromatogram obtained from the Test solution.)
     B. Carry out the test as described in the “Thin-Layer Chromatography” (Appendix 3.1), using silica gel GF254 as the coating substance and a mixture of 90 volumes of toluene and 10 volumes of ethyl acetate as the mobile phase. Apply separately to the plate, 5 μL each of the following two solutions. Prepare solution (A) by diluting 1 mL of the sample with 9 mL of ethanol. For solution (B), dilute 2 mL of citronellal in 9 mL of ethanol. After removal of the plate, allow it to dry in hot air.  Spray the plate with anisaldehyde TS and heat at 105° for 10 minutes; the spot due to citronellal is purple.  The chromatogram obtained from solution (A) shows a purple spot corresponding to the citronellal spot from solution (B). Several other spots of different colours are observed. 

Relative density  0.881 to 0.895 (Appendix 4.9).
Refractive index 1.463 to 1.475, at 20° (Appendix 4.7).
Optical rotation –4° to +1.5°, at 20° (Appendix 4.8).
Composition 1.0 to 5.0 per cent of limonene, 30.0 to 45.0 per cent of citronellal, 2.0 to 4.0 per cent of citronellyl acetate, not more than 2.0 per cent of neral, not more than 2.0 per cent of geranial, 3.0 to 8.0 per cent of geranyl acetate, 9.0 to 15.0 per cent of citronellol and 20.0 to 25.0 per cent of geraniol.  Carry out the determination as described in the “Gas Chromatography” (Appendix 3.4).
     Standard solution  Dilute 25 μL of limonene, 100 μL of citronellal, 25 μL of citronellyl acetate, 25 μL of citral (mixture of neral and geranial), 25 μL of geranyl acetate, 25 μL of citronellol, and 100 μL of geraniol in 5 mL of hexane.
     Test solution The substance to be examined.
     Chromatographic system The chromatographic procedure may be carried out using (a) a fused-silica column (60 m × 0.25 mm) packed with macrogol 20000 (0.2 μm) on silanized diatomaceous support, (b) the injection port and the detector block maintained at 260º, respectively, (c) split ratio 1:100, (d) helium for chromatography as the carrier gas at a flow rate of about 1.0 mL per minute, and (e) a flame ionization detector at 260°. The step gradient of temperature is as follows:

      To determine the suitability of the chromatographic system, chromatograph Standard solution, and record the retention times and peak responses as directed under Procedure: the elution order of the substances is limonene, citronellal, citronellyl acetate, neral, geranial, geranyl acetate, citronellol, and geraniol, and the resolution factor between the geranyl acetate peak and the citronellol peak is not less than 1.2.
      Procedure  Separately inject about 1 μL of Standard solution and 0.2 μL of Test solution into the chromatograph, record the chromatograms, locate and measure the retention times and peak responses of the limonene, citronellal, citronellyl acetate, neral, geranial, geranyl acetate, citronellol, and geraniol peaks in the chromatogram obtained from the Test solution, using the retention times in the chromatogram obtained from the Standard solution.
      Calculation  Calculate the percentage of limonene, citronellal, citronellyl acetate, neral, geranial, geranyl acetate, citronellol, and geraniol in the Oil taken, using the normalization procedure (Appendix 3.9).