Essential oil identification and estimation of its quality is an important and integral process of its qualitative analysis. Their high economic value and extensive usage by various industries help in ensuring its quality, which is a significant aspect of its quality control.

Today GC is an invaluable tool in the identification of essential oils. A complete constituent profile of essential oils is done by GLC analysis and GC-MS is used for the identification of essential oil constituents.

Following are some of the routine tests employed in their identification:

1. Sensory tests: Examination of colour, viscosity, clarity, and odor of an essential oil will give a preliminary indication of its quality. For example, Otto of rose is viscous at lower temperatures due to the congealing of natural waxes present in it. A highly mobile rose oil at low temperature may not be genuine. Similarly, golden green-coloured geranium oil indicates its purity. Simple odor evaluation of essential oils is an effective way to detect their quality and sensory perception because odor detection is considered a highly skilled task.
2. Other physical parameters such as specific gravity, optical rotation, and refractive index are important for establishing the authenticity of an essential oil.
3. TLC Test: TLC is an important separation technique for the detection of volatile oils. TLC of the oil is developed in solvents such as hexane-ethyl acetate (19:1), hexane-chloroform (1:1), toluene-ethylacetate (8:2) using heat-activated TLC plates. Activation is done by spraying with Vanillin-sulphuric acid (0.5 g vanillin in 2 ml concentrated sulphuric acid with 8 ml methanol) and heating at 105°C for full colour development. Mono and sesquiterpene components of the oil are detected by grayish red spots.
4. A GC analysis of an essential oil shall reveal valuable information about its quality. GC chromatogram is a linear graph that charts the presence and distribution of the volatile components of an essential oil. Every detected component of the oil is traced in the form of a peak in the graph. This GC chromatogram is unique for each essential oil and it may be compared with that developed for an authentic sample of the oil. Though the GC profile of essential oil from the same source may vary at different times, with expertise it is possible to identify the quality of an oil from its GC profile. GC with accompanying MS identifies the individual components, along with their relative percentages.