Handbook of essential oils baser

Upon returning home, he worked as a lecturer in pharmacognosy at the school he had earlier graduated, and served as director of Eskisehir I. School of Chemical Engineering between and He was promoted to associate professorship in pharmacognosy in He served as dean of the faculty of pharmacy at Anadolu University , vice-dean of the faculty of pharmacy , head of the department of professional pharmaceutical sciences , head of the pharmacognosy department , member of the University Board and Senate ; , and director of the Medicinal and Aromatic Plant and Drug Research Centre TBAM in Anadolu University.

He was promoted to full professorship in pharmacognosy in Cyprus and director of Graduate Institute of Health Sciences of the same university. His major areas of research include essential oils, alkaloids, and biological, chemical, pharmacological, technological, and biological activity research into natural products. He is listed among the Turks Leading Science. He has published research papers in international refereed journals, papers in Turkish journals, and papers in conference proceedings.

He has published altogether scientific contributions as papers, books, book chapters. According to SCI, his papers were cited His H-index is According to Google Scholar, his publications were cited His H-index is 72; i10 index is He studied pharmacy at the University of Vienna, from where he received his master's degree Mag. Review on essential oils, chemical composition, extraction, and utilization of some conifers in Northwestern Himalayas. Phytotherapy research : PTR. Pharmaceutical Sciences.

Background: Stachys lavandulifolia Vahl is a herbaceous plant distributed in the west and south western Asia. Despite of the wide medicinal uses, there are some reports on toxicity potential of this … Expand. Essential oils and their components are a class of antifungals with potent vapour-phase-mediated anti-Candida activity. Scientific Reports. Comprehensive reviews in food science and food safety. Cookies are used to provide, analyse and improve our services; provide chat tools; and show you relevant content on advertising.

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Vucemilovic, a well done example for the application of essential oils, really, has been kept as it is in the first edition, because an update of the recipes and thus creating a collection of old and new recipes for cooks does not meet the sense of this book.

We hope that also this second edition with the alluring mixture of former, updated, and even new contributions will satisfy the curiosity and needs of all of our readers who share with us the vivid interest in this fascinating natural topic, the essential oils.

He graduated from Eskisehir I. School of Pharmacy with diploma number 1 in and became a research assistant in the pharmacognosy department of the same school. Upon returning home, he worked as a lecturer in pharmacog- nosy at the school he had earlier graduated from and served as director of Eskisehir I.

School of Chemical Engineering between and He was promoted to associate professor- ship in pharmacognosy in He served as dean of the faculty of pharmacy at Anadolu University — , vice dean of the faculty of pharmacy — , head of the department of professional pharmaceutical sci- ences — , head of the pharmacognosy section —present , member of the university board and senate —; , and director of the Medicinal and Aromatic Plant and Drug Research Centre TBAM — in Anadolu University.

He retired from Anadolu University in He was promoted to full professorship in pharmacognosy in His major areas of research include essential oils, alkaloids, and biological, chemical, pharmacological, technological, and bio- logical activity research into natural products. He has published more than papers in international refereed journals more than in SCI journals , papers in Turkish journals, and papers in conference proceedings. He communicated papers in symposia. He is the author of 52 books or book chapters.

Gerhard Buchbauer was born in in Vienna, Austria. In September , he assumed the duties of university assistant at the Institute of Pharmaceutical Chemistry and received his doctorate PhD in pharmacy and philosophy in October with a thesis on synthetic fragrance compounds.

Further scientific edu- cation was practiced postdoc in the team of Professor C. In November , he was appointed as a full professor of pharmaceutical chemistry, University of Vienna; in , he was elected as head of this institute. He retired in October He is married since and had a son in Among others, he is still a member of the permanent scientific committee of International Symposium on Essential Oils ISEO ; a member of the scientific committee of Forum Cosmeticum , , , and ; a member of numerous editorial boards e.

Based on the sound interdisciplinary education of pharmacists, it was possible to establish an almost completely neglected area of fragrance and flavor chemistry as a new research discipline within the pharmaceutical sciences.

Because of our efforts, it is possible to show and to prove that these small molecules possess more properties than merely emitting a good odor. Now, this research team has gained a worldwide scientific reputation documented by more than scientific publications, about invited lectures, and about contributions to symposia, meetings, and congresses, as short lectures and poster presentations.

Erich Schmidt Sean V. Among other qualities, they pos- sess various biological properties. This book intends to make the reader acquainted with all aspects of EOs and their constituent aromachemicals ranging from chemistry, pharmacology, biological activity, production, trade uses, and regulatory aspects.

Traditional and modern production techniques of EOs are illustrated and discussed in Chapter 4. On account of the com- plexity of these natural products, the toxicological or biochemical testing of an EO will always be the sum of its constituents, which either act in a synergistic or in an antagonistic way with one another. Therefore, the chemical characterization of an EO is very important for the understanding of its biological properties. The constituents of these natural mixtures, upon being absorbed into the blood stream of humans or animals, get metabolized and eliminated.

Here, the emphasis is put on the central nervous system and on psy- chopharmacology whereas Chapter 10, Section Another contribu- tion only deals with antimicrobial activities of those EOs that are monographed in the European Pharmacopoeia. It completes the series of contributions dealing with the biological properties of EO regarded from various sides and standpoints. Chapters 14 and 15 by the world-renowned experts Y. Asakawa and Y. Enzymes in microorganisms and tissues metabolize EO constituents in similar ways by adding mainly oxygen function to molecules to render them water soluble, which facilitates their metabolism.

This is also seen as a means of detoxification for these organisms. Many interesting and valuable novel chemicals are biosynthesized by this way. These products are also considered natural since the substrates are natural. Encapsulation is a technique widely utilized in pharmaceutical, chemical, food, and feed industries to render EOs more manageable in formulations. Industrial uses of EOs are covered in an infor- mative chapter from a historical perspective.

Here, the holistic point of view rather than too scientific a way of understanding EOs is the topic, simply to show that these volatile natural plant products can add to the feel-good factor for users. EOs are not only appealing to humans but also to animals. The EO industry is highly complex and fragmented and the trade of EOs is rather conserva- tive and highly specialized.

EOs are produced and utilized worldwide in both industrialized and developing countries. Storage and transport of EOs are crucial issues since they are highly sensitive to heat, moisture, and oxygen.

Therefore, special precautions and strict regulations apply for their handling in storage and transport. Finally, the regulatory affairs of EOs are dealt with in Chapter 22 to give a better insight to those interested in legislative aspects. This book is hoped to satisfy the needs of EO producers, traders, and users as well as researchers, academicians, and legislators who will find the most current information given by selected experts under one cover.

In this treatise Prof. Nemeth-Zamborini discusses the reasons why variability of components often occurs in EOs.

Now, these EOs are adulterated. Other examples of such processes are described very impressively in this chapter. Chapters 2, 5, 12, 15, 19 through 21, 23, and 25 remained as written in the first edition. The former Chapter 9 has been updated and divided into two chapters, now listed as Chapters 10 and In spite of the obscured beginning of the use of aromatic plants in prehistoric times to prevent, palliate, or heal sicknesses, pollen analyses of Stone Age settlements indicate the use of aromatic plants that may be dated to 10, BC.

One of the most important medical documents of ancient Egypt is the so-called Papyrus Ebers of about BC, a 20 m long papyrus, which was purchased in by the German Egyptologist G. Ebers, for whom it is named, containing some formulas and remedies, including aromatic plants and plant products like anise, fennel, coriander, thyme, frankincense, and myrrh.

Much later, the ancient Greek physician Hippocrates — BC , who is referred to as the father of medicine, mentioned in his treatise Corpus Hippocratium approximately medicinal plants inclusive of aromatic plants and described their efficacies. One of the most important herbal books in history is the five-volume book De Materia Medica, written by the Greek physician and botanist Pedanius Dioscorides ca.

In the course of his numerous travels all over the Roman and Greek world seeking for medicinal plants, he described more than medicinal plants and respective remedies. His treatise, which may be considered a precursor of modern pharmacopoeias, was later translated into a variety of languages. Dioscorides, as well as his contemporary Pliny the Elder 23—79 , a Roman natural historian, mention besides other facts turpentine oil and give some limited information on the methods in its preparation.

Many new medicines and ointments were brought from the east during the Crusades from the eleventh to the thirteenth centuries, and many herbals, whose contents included recipes for the use and manufacture of essential oil, were written during the fourteenth to the sixteenth centuries.

Theophrastus von Hohenheim, known under the name Paracelsus — , a physician and alchemist of the fifteenth century, defined the role of alchemy by developing medicines and extracts from healing plants. The roots of distillation methods are attributed to Arabian Alchemists centuries with Avicenna — describing the process of steam distillation, who is credited with inventing a coiled cooling pipe to prepare essential oils and aromatic waters.

The first description of distilling essen- tial oils is generally attributed to the Spanish physician Arnaldus de Villa Nova — in the thirteenth century. However, in , a perfectly preserved terracotta apparatus was found in the Indus Valley, which is dated to about BC and which is now displayed in a museum in Taxila, Pakistan. It looks like a primitive still and was presumable used to prepare aromatic waters.

Further findings indicate that distillation has also been practiced in ancient Turkey, Persia, and India as far back as BC. At the beginning of the sixteenth century appeared a comprehensive treatise on distillation by Hieronymus Brunschwig ca. He described the process of distillation and the different types of stills in his book Liber de arte Distillandi de compositis Strasbourg and with numerous block prints.

Although obviously endeavoring to cover the entire field of distillation techniques, he mentions in his book only the four essential oils from rosemary, spike lavender, juniper wood, and the turpentine oil. Just before, until the Middle Ages, the art of distillation was used mainly for the preparation of aromatic waters, and the essential oil appearing on the surface of the distilled water was regarded as an undesirable by-product. He stresses that the art of distillation is a quite recent invention and not an ancient invention and has not been used earlier.

In the Dispensatorium Pharmacopolarum of Valerius Cordus, published in Nuremberg in , only three essential were listed; however, the second official edition of the Dispensatorium Valerii Cordi issued in , 61 distilled oils were listed illustrating the rapid development and acceptance of essential oils. In that time, the so-called Florentine flask has already been used for separating the essential oil from the water phase. The German J. Glauber — , who can be regarded as one of the first great industrial chemists, was born in the little town Karlstadt close to Wuerzburg.

In addition, he improved numerous different other chemical processes and especially new distillation devices also for the preparation of essential oils from aromatic plants. However, it lasted until the nineteenth century to get any real understanding of the composition of true essential oils. Dumas — who analyzed some hydrocarbons and oxygen as well as sulfur- and nitrogen-containing constituents.

He published his results in The French researcher M. Berthelot characterized several natural substances and their rearrangement products by optical rotation. However, the most important investigations have been performed by O. Wallach, an assistant of Kekule. He realized that several terpenes described under different names according to their botanical sources were often, in fact, chemically identical.

He, therefore, tried to isolate the individual oil constituents and to study their basic properties. He employed together with his highly qualified coworkers Hesse, Gildemeister, Betram, Walbaum, Wienhaus, and others fractional dis- tillation to separate essential oils and performed reactions with inorganic reagents to characterize the obtained individual fractions.

The reagents he used were hydrochloric acid, oxides of nitrogen, bromine, and nitrosyl chloride—which was used for the first time by W. Tilden —by which frequently crystalline products have been obtained. At that time, hydrocarbons occurring in essential oils with the molecular formula C10H16 were known, which had been named by Kekule terpenes because of their occurrence in turpentine oil.

Constituents with the molecular formulas C10H16O and C10H18O were also known at that time under the generic name camphor and were obviously related to terpenes. The prototype of this group was camphor itself, which was known since antiquity. In , Wallach characterized the terpenes pinene, camphene, limonene, dipentene, phellandrene, terpinolene, fenchene, and sylvestrene, which has later been recognized to be an artifact.

During —, Wallach wrote about articles that are summarized in his book Terpene und Campher Wallach, compiling all the knowledge on terpenes at that time, and already in , he suggested that the terpenes must be constructed from isoprene units. In addition to Wallach, the German chemist A. Since , he devoted considerable work to the structures and properties of cyclic terpenes von Baeyer, Besides his contributions to several dyes, the investigations of polyacetylenes, and so on, his contributions to theoretical chemistry including the strain theory of triple bonds and small carbon cycles have to be mentioned.

The frequently occurring acyclic mono- terpenes geraniol, linalool, citral, and so on have been investigated by F. Semmler and the Russian chemist G.

Wagner , who recognized the importance of rearrangements for the elucidation of chemical constitution, especially the carbon-to-carbon migration of alkyl, aryl, or hydride ions, a type of reaction that was later generalized by H. Meerwein as Wagner—Meerwein rearrangement. More recent investigations of J. Read, W. Schmidt, W. Treibs, and V. Prelog were mainly devoted to disentangle the stereochemical structures of menthols, carvomenthols, borneols, fenchols, and pinocampheols, as well as the related ketones see Gildemeister and Hoffmann, A significant improvement in structure elucidation was the application of dehydrogenation of sesqui- and diterpenes with sulfur and later with selenium to give aromatic compounds as a major method, and the application of the isoprene rule to terpene chemistry, which have been very effi- ciently used by L.

Ruzicka in Zurich, Switzerland. After numerous investigations, W. Treibs has been able to isolate the crystalline caryophyllene epoxide from the autoxidation products of clove oil, and F. This suggestion was later confirmed by the English chemist D. The application of ultraviolet UV spectroscopy in the elucidation of the structure of terpenes and other natural products was extensively used by R.

Woodward in the early forties of the last century. He was awarded the Nobel Prize in Chemistry in However, it was not until the introduction of chromatographic separation methods and nuclear magnetic resonance NMR spectroscopy into organic chemistry that a lot of further structures of terpenes were elucidated. The almost exponential growth in our knowledge in that field and other essential oil constituents is essentially due to the considerable advances in ana- lytical methods in the course of the last half century.

In water or hydrodistillation, the chopped plant material is submerged and in direct contact with boiling water. In steam distillation, the steam is produced in a boiler separate of the still and blown through a pipe into the bottom of the still, where the plant material rests on a perforated tray or in a basket for quick removal after exhaustive extraction.

In addition to the aforementioned distilla- tion at atmospheric pressure, high-pressure steam distillation is most often applied in European and American field stills, and the applied increased temperature significantly reduces the time of distilla- tion. The high-pressure steam-type distillation is often applied for peppermint, spearmint, lavandin, and the like.

The condensed distillate, consisting of a mixture of water and oil, is usually separated in a so-called Florentine flask, a glass jar, or more recently in a receptacle made of stainless steel with one outlet near the base and another near the top. There, the distillate separates into two layers from which the oil and the water can be separately withdrawn.

Generally, the process of steam distillation is the most widely accepted method for the production of essential oils on a large scale. Expression or cold pressing is a process in which the oil glands within the peels of citrus fruits are mechanically crushed to release their content.

There are several different processes used for the isola- tion of citrus oils; however, there are four major currently used processes. Those are pellatrice and sfumatrice—most often used in Italy—and the Brown peel shaver as well as the FMC extractor, which are used predominantly in North and South America. For more details, see, for example, Lawrence All these processes lead to products that are not entirely volatile because they may contain cou- marins, plant pigments, and so on; however, they are nevertheless acknowledged as essential oils by the International Organization for Standardization, the different pharmacopoeias, and so on.

In contrast, extracts obtained by solvent extraction with different organic solvents, with liquid carbon dioxide or by supercritical fluid extraction SFE may not be considered as true essential oils; however, they possess most often aroma profiles that are almost identical to the raw material from which they have been extracted.

They are therefore often used in the flavor and fragrance industry and in addition in food industry, if the chosen solvents are acceptable for food and do not leave any harmful residue in food products. The most often used device is the circulatory distillation apparatus, basing on the publication of Clevenger in and which has later found various modifications.

One of those modified apparatus described by Cocking and Middleton has been introduced in the European pharmacopoeia and several other pharmacopoeias. This device consists of a heated round-bottom flask into which the chopped plant material and water are placed and which is connected to a vertical condenser and a graduated tube, for the volumetric determination of the oil. At the bottom of the tube, a three-way valve permits to direct the water back to the flask, since it is a continuous closed-circuit distillation device, and at the end of the distillation process to separate the essential oil from the water phase for further investigations.

The length of distillation depends on the plant material to be investigated; however, it is usually fixed to 3—4 h. For the volumetric determination of the essential oil content in plants according to most of the pharmacopoeias, a certain amount of xylene—usually 0. The volume of essential oil can be determined in the graduated tube after subtracting the volume of the applied xylene.

Improved constructions with regard to the cooling system of the aforementioned distillation apparatus have been published by Stahl and Sprecher and, in publications of Kaiser and Lang and Mechler and Kovar , various apparatus used for the determination of essential oils in plant material are discussed and depicted.

A further improvement was the development of a simultaneous distillation—solvent extraction device by Likens and Nickerson in see Nickerson and Likens, The device permits continuous concentration of volatiles during hydrodistillation in one step using a closed-circuit distillation system. The water distillate is continuously extracted with a small amount of an organic- and water-immiscible solvent.

Although there are two versions described, one for high- density and one for low-density solvents, the high-density solvent version using dichloromethane is mostly applied in essential oil research. It has found numerous applications, and several modi- fied versions including different microdistillation devices have been described e. A sample preparation technique basing on Soxhlet extraction in a pressurized container using liquid carbon dioxide as extractant has been published by Jennings This device produces solvent-free extracts especially suitable for high-resolution gas chromatography GC.

As a less time- consuming alternative, the application of microwave-assisted extraction has been proposed by sev- eral researchers, for example, by Craveiro et al. This flask was placed into a microwave oven and passed by a flow of air. The oven was heated for 5 min and the obtained mixture of water and oil collected in a small and cooled flask. The obtained analytical results have been compared with the results obtained by conventional distillation and exhibited no qualitative differences; however, the percentages of the individual components varied significantly.

A different approach yielding solvent-free extracts from aromatic herbs by means of microwave heating has been presented by Lucchesi et al. The potential of the applied technique has been compared with conventional hydrodistillation showing substantially higher amounts of oxygenated compounds at the expense of monoterpene hydrocarbons. In the past, numerous attempts have been made to minimize conventional distillation devices.

As an example, the modified Marcusson device may be quoted Bicchi et al. The analytical results proved to be identical with those obtained by conventional distillation. Microversions of the distillation—extraction apparatus, described by Likens and Nickerson, have also been developed as well for high-density Godefroot et al.

The main advantage of these techniques is that no further enrichment by evaporation is required for subsequent gas chromatographic investigation. By means of a new developed micro-hydrodistillation device, the volatile constituents of very small amounts of plant material have been separated.

This vial, which is placed in a heating block, is connected with a cooled receiver vial by a 0. By temperature-programmed heating of the sample vial, the water and the volatile constituents are vaporized and passed through the capillary into the cooled receiver vial. There, the volatiles as well as water are condensed and the essential oil collected in pentane for further analy- sis.

The received analytical results have been compared to results from identical samples obtained by conventional hydrodistillation showing a good correlation of the qualitative and quantitative composition. A simple device for rapid extraction of volatiles from natural plant drugs and the direct transfer of these substances to the starting point of a thin-layer chromatographic plate has been described by Stahl a and in his subsequent publications.

A small amount of the sample ca. The tip of the glass tube projects ca. Before introducing the glass tube, it is sealed with a silicone rubber membrane. This simple technique has proven useful for many years in numerous investigations, especially in quality control, identification of plant drugs, and rapid screening of chemical races.

In addition to the aforementioned micro-hydrodistillation with the so-called TAS procedure T, thermomicro and transfer; A, application; S, substance , several further applications, for example, in structure elucidation of isolated natural compounds such as zinc dust distillation, sulfur and selenium dehydrogenation, and catalytic dehydrogenation with palladium, have been described in the microgram range Stahl, Therefore, only direct sampling from secretory cavities and glandular trichomes and properly performed successive analysis may furnish reliable results.

One of the first inves- tigations with a kind of direct sampling has been performed by Hefendehl , who isolated the glandular hairs from the surfaces of Mentha piperita and Mentha aquatica leaves by means of a thin film of polyvinyl alcohol, which was removed after drying and extracted with diethyl. The composition of this product was in good agreement with the essential oils obtained by hydrodistillation.

In the same year, Amelunxen et al. They found identical qualitative composi- tion of the oil in both types of hairs, but differing concentrations of the individual components. Further studies have been performed by Henderson et al. In the latter study, significant differences regarding the oil composition of the hydrodistilled oil and the oil extracted by means of glass capillaries from the trichomes were observed.

Their final conclusion was that the analysis of the respective essential oil is mainly an analysis of artifacts, formed during distillation, and the gas chromatographic analysis.

It is a means of separating the volatiles from a liquid or solid prior to gas chromatographic analysis and is preferably used for samples that cannot be directly injected into a gas chromatograph. The applied techniques are usually classified accord- ing to the different sampling principles in static HS analysis and dynamic HS analysis.

After the sample has reached equilibrium with its vapor in equilibrium, the distribution of the analytes between the two phases depends on their partition coefficients at the preselected temperature, the time, and the pressure , an aliquot of the vapor phase can be withdrawn with a gas-tight syringe and subjected to gas chro- matographic analysis.

A simple method for the HS investigation of herbs and spices was described by Chialva et al. After grinding the herb and until thermodynamic equilibrium is reached, the HS sample can be withdrawn through the valve and injected into a gas chromatograph. Eight of the obtained capillary gas chromatograms are depicted in the paper of Chialva and compared with those of the respective essential oils exhib- iting significant higher amounts of the more volatile oil constituents.

However, one of the major problems with static HS analyses is the need for sample enrichment with regard to trace compo- nents. Therefore, a concentration step such as cryogenic trapping, liquid absorption, or adsorption on a suitable solid has to be inserted for volatiles occurring only in small amounts.

A versatile and often-used technique in the last decade is solid-phase microextraction SPME for sampling vola- tiles, which will be discussed in more detail in a separate paragraph. Since different other trapping procedures are a fundamental prerequisite for dynamic HS methods, they will be considered in the succeeding text. A comprehensive treatment of the theoretical basis of static HS analysis including numerous applications has been published by Kolb and Ettre , However, care has to be taken if grinded plant material has to be investigated, since disruption of tissues may initiate enzymatic reactions that may lead to formation of volatile artifacts.

After stripping the plant material with gas in a closed vessel, the released volatile compounds are passed through a trap to collect and enrich the sample. This must be done because sample injection of fairly large sample volumes results in band broadening causing.

The following three techniques are advisable for collecting the highly diluted volatile sample according to Schaefer and Schreier with numerous references. Cryogenic trapping can be achieved by passing the gas containing the stripped volatiles through a cooled vessel or a capillary in which the volatile compounds are condensed Kolb and Liebhardt, The most convenient way for trapping the volatiles is to utilize part of the capillary column as a cryogenic trap.

A simple device for cryofocusing of HS volatiles by using the first part of capillary column as a cryogenic trap has been shown in the aforementioned reference inclusive of a discus- sion of the theoretical background of cryogenic trapping. A similar on-column cold trapping device, suitable for extended period vapor sampling, has been published by Jennings A different approach can be used if large volumes of stripped volatiles have to be trapped using collection in organic liquid phases.

In this case, the volatiles distribute between the gas and the liquid, and efficient collection will be achieved, if the distribution factor K is favorable for solving the stripped compounds in the liquid. A serious drawback, however, is the necessity to concentrate the obtained solution prior to GC with the risk to lose highly volatile compounds.

This can be overcome if a short-packed GC column is used containing a solid support coated with a suitable liquid. Novak et al. There, the volatiles were desorbed under heating and flushed onto the GC col- umn. In , Bichi et al. The plants under investigation were placed in a glass bell into which the trapping capillary was introduced through a rubber septum, while the other end of the capillary has been connected to pocket sampler.

In order to trap even volatile monoterpene hydrocarbons, a capil- lary length of at least 50 cm and sample volume of maximum mL have to be applied to avoid loss of components through breakthrough. The trapped compounds have been subsequently online thermally desorbed, cold trapped, and analyzed. Finally, a type of enfleurage especially designed for field experiments has been described by Joulain to trap the scents of freshly picked flowers. Around g flowers were spread on the grid of a specially designed stainless steel device and passed by a stream of ambient air, supplied by an unheated portable air drier.

The stripped volatiles are trapped on a layer of purified fat placed above the grid. After 2 h, the fat was collected and the volatiles recovered in the laboratory by means of vacuum distillation at low temperature. With a third often applied procedure, the stripped volatiles from the HS of plant material and especially from flowers are passed through a tube filled with a solid adsorbent on which the volatile compounds are adsorbed.

Common adsorbents most often used in investigations of plant volatiles are above all charcoal and different types of synthetic porous polymers. Activated charcoal is an adsorbent with a high adsorption capacity, thermal and chemical stability, and which is not deac- tivated by water, an important feature, if freshly collected plant material has to be investigated. Numerous applications have been described using this special type of activated charcoal, for example, by Kaiser in a great.

The trapped components can be recovered either by thermal desorption or by sol- vent elution, and the recoveries can be different depending on the applied adsorbent Cole, Another very important criterion for the selection of a suitable adsorbent for collecting HS samples is the breakthrough volume limiting the amount of gas passing through the trap.

A comprehensive review concerning HS gas chromatographic analysis of medicinal and aro- matic plants and flowers with references, covering the period from to has been published by Bicchi and Joulain in , thoroughly describing and explaining the different meth- odological approaches and applications.

Among other things, most of the important contributions of the Finnish research group of Hiltunen and coworkers on the HS of medicinal plants and the optimization of the HS parameters have been cited in the mentioned review. Sample preparation is based on sorption of analytes from a sample onto a coated fused silica fiber, which is mounted in a modified GC syringe. After introducing the coated fiber into a liquid or gaseous sample, the compounds to be analyzed are enriched accord- ing to their distribution coefficients and can be subsequently thermally desorbed from the coating after introducing the fiber into the hot injector of a gas chromatograph.

The fiber can be drawn into the syringe needle to prevent damage. To use the device, the needle is pierced through the septum that seals the sample vial. Then, the plunger is depressed lowering the coated fiber into the liquid sample or the HS above the sample. After sorption of the sample, which takes some minutes, the fiber has to be drawn back into the needle and withdrawn from the sample vial. By the same procedure, the fiber can be introduced into the gas chromatograph injector where the adsorbed substances are thermally desorbed and flushed by the carrier gas into the capillary GC column.

SPME fibers can be coated with polymer liquid e. The selectivity and capacity of the fiber coating can be adjusted by changing the phase type or thickness of the coating on the fiber according to the properties of the compounds to be analyzed. The influence of fiber coatings on the recovery of plant volatiles was thoroughly investigated by Bicchi et al. Details concerning the theory of SPME, technology, its application, and spe- cific topics have been described by Pawliszyn and references cited therein.

A number of dif- ferent applications of SPME in the field of essential oil analysis have been presented by Kubeczka a. Parameters governing recovery of analytes from a sample are parti- tioning constants and the phase ratio between the sorbent and liquid or gaseous sample. Therefore, basing on theoretical considerations, a procedure for sorptive enrichment with the sensitivity of packed PDMS beds Baltussen et al. After certain stirring time, the stir bar has to be removed, introduced into a glass tube, and transferred to thermal desorption instrument.

After desorption and cryofocusing within a cooled programmed temperature vaporiza- tion PTV injector, the volatiles were transferred onto the analytical GC column. Comparison of SPME and the aforementioned stir bar sorptive extraction SBSE technique using identical phases for both techniques exhibited striking differences in the recoveries, which has been attributed to ca.

A comprehensive treatment of SBSE, discussion of the principle, the extraction procedure, and numerous applications was recently been published by David and Sandra A further approach for sorptive enrichment of volatiles from the HS of aqueous or solid samples has been described by Tienpont et al. This technique implies the sorption of volatiles into PDMS that is chemically bound on the surface of a glass rod support.

The device consists of a ca. This last part is covered with PDMS chemically bound to the glass surface. After sampling for 45 min, the bar was put into a glass tube for thermal desorption, which was performed with a TDS-2 thermodesorption unit Gerstel.

After desorption and cryofocusing within a PTV injector, the volatiles were transferred onto the analytical GC column. Several examples referring to the application of HSSE in HS analysis of aromatic and medicinal plants inclusive of details of the sampling procedure were described by Bicchi et al. A part of them has been replaced nowadays by either more effective or easier-to-handle techniques, while other methods maintained their significance and have been permanently improved. Before going into detail, the analytical facilities in the sixties of the last century should be considered briefly.

The methods available for the analysis of essential oils have been at that time Table 2. In the following years, several additional techniques were developed and applied to essential oils analysis, including high-performance liquid chromatography HPLC ; different kinds of counter- current chromatography CCC ; supercritical fluid chromatography SFC , including multidimen- sional coupling techniques, C NMR, near IR NIR , and Raman spectroscopy; and a multitude of so-called hyphenated techniques, which means online couplings of chromatographic separation devices to spectrometers, yielding valuable structural information of the individual separated com- ponents that made their identification feasible.