Identification Test:

1. Citral is very sensitive to oxidizing agents (even exposure to air) and yields linalool which have intense yellow colour.

2. An alcoholic solution of Sudan III is added to the test sample. Red colour obtained by the globules indicates the presence of citral in the volatile oil.

3. A drop of tincture alkane is added to the test sample. Red colour indicates the presence of citral in the volatile oil

4. Geranial with Tollen’s reagent (ammoniacal silver nitrate) gives geranic acid (C19H15COOH).

5. Geranial upon hydrogenation with sodium amalgum in acidic solution gives citronellal and citronellol.

6. Geranial gets converted into ρ-cymene on treatment with potassium bisulphate or dilute sulphuric acid.

7. When citral interacts with acetone, it forms pseudo-ionone or Ψ–ionone. The aliphatic ketone pseudo-ionone undergoes cyclisation with variety of reagents like sodium acetate, concentrated sulphuric acid, formic acid, dilute mineral acid etc and yields β-ionone and α-ionone.

Analysis

• Citral can be analysed in a Shimadzu Gas Liquid Chromatograph (Model GC - 14B) coupled with a non-polar DB-5 capillary column [30m × 0.250mm and 0.25-micron Internal Diameter (ID)] using a Flame Ionisation Detector (FID).

• The instrument is connected to a computer having the CLASS GC 10 software that is used for data analysis.

• Retention Indices (RI), using n -alkanes (octane, nonane, decane, dodecane, octadecane, eicosane, docosane, tetracosane, and hexacosane) are used as the basis.

• The percentage of each compound is calculated by dividing the peak area by the total area of component peaks.

• The temperature range is maintained from 50 - 250°C, with a temperature programme rate of 20°C/min, starting at 2 minutes and finishing at 10 minutes.

• The detector and injection temperatures are maintained at 250°C.

• The Retention Indices (RI) of standard compounds that match with the RI of the unknowns is detected by GC.

• By comparing the RI match with a standard compound, citral is confirmed.