Many theories have been proposed in an attempt to explain how humans perceive odours. Those that are still taken seriously can be grouped into two classes, which I label recognition and vibration. In both of these, it is proposed that an odorant molecule comes into contact with a receptor and that the nature of the […]


CHARLES SELL BACKGROUND The five senses (sight, hearing, taste, smell and touch) developed in living organisms as a means of giving them information about their environment. Chemoreception was probably the first of the senses to appear and is present in very simple, primitive species. The basic mechanism for detection of chemical signals from outside these […]


The headspace is the air above or around a fragrant substance that contains the volatile compounds. This can be collected for analysis when extraction of the volatiles from the material is not viable. This technique has been extensively developed for the collection and analysis of flower volatiles, since many flowers do not yield an extract […]


Once a fraction or component of an essential oil or extract has been isolated, its identity needs to be determined. A familiar or common chemical is usually considered to be positively identified if its retention time on a given GC phase and its mass spectrum match those of a reference material. However, the identification of […]

Preparative Liquid Chromatography

Liquid chromatography (Hostettman et al, 1986) in its many forms is a separation technique based on the polarity of the analytes and their partition between the mobile and stationary phases, and is therefore complementary to fractional distillation, which separates materials by their boiling point. The usual sequence for fractionating an essential oil or extract is […]

GC Detectors

The most common detector is the flame ionization detector (FID). The outlet from the column is directed into a carefully controlled hydrogen flame. The electrical potential across the flame is measured continu­ously, as this changes when an organic compound elutes from the column and is ionized in the flame. The analogue signal from the detector […]

GC Columns

The most common form of GC columns used in the fragrance industry is the wall-coated, open tubular (WCOT) type. These are made of fused silica tubing coated with a thin film of stationary phase on the inside and covered with polyamide on the outside for protection. Fused silica columns are usually between 25 m and […]

GC Injection Systems

Many specialized injection systems are used with the GC in the modern laboratory to deliver the complete sample to the column without alteration. The conventional injection method is simply to inject a small volume (about 1 /Л) of a dilution of the sample using a syringe with a fine needle, which pierces a silicon rubber […]

Gas-Liquid Chromatography

Usually referred to simply as GC, this is one of the most important and widely used analytical techniques in the fragrance industry, as it is ideally suited to the volatile compounds that are the basis of the industry. It is a means of separating a complex mixture into its components and subsequently quantifying the individual […]


Extraction Steam distillation is the main commercial extraction procedure for the production of essential oils from almost any type of plant material. Solvent extraction is also used commercially and yields a resinoid, concrete or absolute according to the solvents and techniques used (see Chapter 4). Both steam distillation and solvent extraction are used on a […]