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Analysis of Essential Oils Using GC-
FID And GC-MS
Research Project
Submitted to the Department of (Chemistry) in the Partial Fulfillment of the
Requirements for the B.A in (Salahaddin University-Erbil)
By:
Sara Kamaran Salahaddin
Supervised by:
Dr. Ibrahim Qadr Saeed
April - 2021
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DEDICATION
Thanks to Allah for helping us to fulfill this work and bring it to this final
shape. Thanks to my parents who have taught us the way of life, I wish to
express our special thanks to our supervisor “Dr. Ibrahim Qadr Saeed” for
his guidance in planning for this research.
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SUPERVISOR’S CERTIFICATION
I certify that the research project titled “Analysis of essential oils using GC-
FID and GC MS was done under my supervision at the department of
chemical, College of Science, Salahaddin University –Erbil. In the partial
fulfillment of ‘The requirement for the degree of Bachelor of Science in
Chemistry’.
Supervisor
Signature:
Name: Dr. Ibrahim Qadr Saeed
Date: / /
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Essential oils are valuable components extracted from plants. Advanced
analytical methods are needed for analyzing and identifying their ingredients to
ensure that a product's description reflects its true composition and origin. The
analysis of essential oils by Gas-Chromatography (GC) is a widespread method
for checking the composition of essential oils. When Gas-Chromatography
coupled with mass spectroscopy or with flame ionization detector (FID), it can
be used to analyze and identify many essential oils precisely and accurately. In
this research we reported some essential oils analysis by using GC-MS and GC-
FID, that have been done previously by researchers. Many essential oils in
different plant sources have been extracted, analyzed and identified with
appreciable accuracy and precision. GC-MS and GC-FID found to be important
methods for analyzing essential oils.
Keywords: Gas chromatography, GC-MS, GC-FID, Essential oils.
ABSTRACT
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LIST OF CONTENTS
Sec. No Title Page No
Chapter One…………………………………………………………………..6
1. Introduction ............................................................................................................................... 6
Chapter Two…………………………………………………………………...8
2. Essential oils .............................................................................................................................. 8
Chapter Three ………………………………………………………………..10
3.Gas Chromatography……………………………………………………..14
3.1 principle of GC-MS ..................................................................................................... 17
3.2 Principle of GC-FID .................................................................................................... 18
Chapter Four…...…………………………………………………………….21
4. Determination of essential oils using GC-MS In literature .......................... 21
4.1 Determination of essential oils using GC-FID In literature ....................... 22
5 Conclusion. ............................................................................................................................ 23
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CHAPTER ONE
1. Introduction
Polygonum minus Huds, commonly known as kesum, is widely used in
Malaysian cooking, and several traditional practices utilise the leaves and stems
of this plant ( Burkill,J.,1966 ). Kesum is an aromatic plant that produces high
levels of essential oil (72.54%) containing aliphatic aldehydes.
(Yaacob,K.B.,1987) identified decanal (24.36%) and dodecanal (48.18%) as the
two dominant aldehydes that contribute to the flavour of kesum. Apart from
decanal and dodecanal, Yaacob also found that kesum contains 1- decanol
(2.49%), 1-dodecanol (2.44%), undecanal (1.77%), tetradecanal (1.42%), 1-
undecanol (1.41%), nonanal (0.86%), 1-nonanol (0.76%), and β-caryophyllene
(0.18%).
As a result, kesum is believed to have great potential as a natural source of
aliphatic aldehydes, which could be useful as food additives and in the perfume
industry. With the development of botanical drugs, including traditional herbal
medicines, analysis of their bioactive components is becoming more popular.
Many botanical drugs have bioactive components in their essential oils, so
characterization of plant essential oils it is an important and meaningful task. Gas
chromatography (GC) or gas chromatography-mass spectroscopy (GC-MS) are
used almost exclusively for the qualitative analysis of the volatiles. Natural
essential oils are usually mixtures of terpenoids (mainly monoterpenoids and
sesquiterpenoids), aromatic compounds and aliphatic compounds. As mass
spectra of these compounds are usually very similar, peak identification often
becomes very difficult and sometimes impossible. In order to address the
qualitative determination of composition of complex samples by GC-MS and to
increase the reliability of the analytical results, it is necessary to utilize retention
indices identities ( Wagner, C.; Sefkow, M.; Kopka, J. , 2003) . Meanwhile,
comprehensive, two-dimensional gas chromatography (GC×GC) also has been
extensively applied in the essential oil study (Marriott, P.; Shellie, R. , 2002).
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This technique has also been successfully used in the industrial analysis of
plant materials to improve component separation and identification. In addition,
an analysis of Artemisia annua L. volatile oils using multi-dimensional gas
chromatography has indicated that this technique can achieve the complete
separation of a wide range of terpenes (Ma, C.; Want, H.; Lu, X. , 2007 ). The
objective of this study was to demonstrate different gas chromatography
approaches to analyses the composition of the essential oils of kesum, with the
hope that the improved component separation and identification would allow for
a determination of unidentified minor components that may strongly influence
the overall quality of the oil.
The combined use of GC-FID and the coupling of GC with
Photospectroscope and mass spectrometry (MS) as well as with olfactory
evaluation (GC sniffing technique) renders the analysis of complex natural
product systems more efficient. Additional information from GC (e.g. Covets
indices and use of chiral phases), FTIR spectra (functional groups), MS spectra
(structure and isotope information as well as molecular weight) and from
olfactory detection (qualitative and quantitative odor value) allows the
determination of the identity of single compounds even in complex mixtures
more effectively and rapidly, and the analytical data can be further evaluated in
additional steps (e.g. library search and multivariate data analysis.
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CHAPTER TWO
2. Essential oils
The term essential oil dates back to the sixteenth century and derives
from the drug Quinta essentia, named by Paracelsus von Hohenheim of
Switzerland (Guenther, E. 1948) . Essential oils or “essences” owe their
name to their flammability. Numerous authors have attempted to provide a
definition of essential oils. The French Agency for Normalization: Agence
Française de Normalisation (AFNOR) gives the following definition (NF T
75-006): “The essential oil is the product obtained from a vegetable raw
material, either by steam distillation or by mechanical processes from the
epicarp of Citrus, or “dry”” distillation. The essential oil is then separated
from the aqueous phase by physical means This definition encompasses
products obtained always from vegetable raw material, but using other
extraction methods, such as using non-aqueous solvents or cold absorption.
Thus, we can define four types of products ( Carette A.S.2000).
Essential oils are soluble in alcohol, ether, and fixed oils, but insoluble in
water. These volatile oils are generally liquid and colorless at room
temperature. They have a characteristic odor, are usually liquid at room
temperature and have a density less than unity, with the exception of a few
cases (cinnamon, sassafras, and vetiver). They have a refractive index and a
very high optical activity. These volatile oils contained in herbs are
responsible for different scents that plants emit. They are widely used in the
cosmetics industry, perfumery, and also aromatherapy. The latter is intended
as a therapeutic technique including massage, inhalations, or baths using
these volatile oils.
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The last key will serve as chemical signals allowing the plant to control or
regulate its environment (ecological role): attraction of pollinating insects,
repellent to predators, inhibition of seed germination, or communication
between plants (emission signals chemically signaling the presence of
herbivores, for example).
8
EOs are usually lucid and mobile liquids, but a few are solid, such as orris, or
semisolid, such as guaiac wood, at room temperature. The majority of EOs are
colorless or pale yellow, although a few are deeply colored, such as blue chamomile,
and European valerian, which is green (Tisserand and Young, 2013). The typical odor
of EOs depends on the organs, species, and origins of plants. They are volatile oils with
a high refractive index and optimal rotation, as the result of many asymmetrical
compounds. The relative density of EOs is commonly lower than
That of water, but several exceptions exists. EOs are usually recognized as
hydrophobic, but they are largely soluble in fats, alcohols, and most organic solvents.
Moreover, they have sensitivity to being oxidized to form resinous products through
polymerization (Li et al., 2014).
Organoleptic and physical characteristics of essential oils
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EO-bearing plants belong to various genera distributed in around 60 families.
The major plant families are well known for their ability to produce EOs of
medicinal and industrial value, and include Alliaceae, Apiaceae, Asteraceae
(Compositae), Lamiaceae (Labiatae), Myrtaceae, Poaceae, Cupressaceae,
Lauraceae, Pinaceae, Zingiberaceae, and Rutaceae (Hammer and Carson, 2011;
Tisserand and Young, 2013; Vigan, 2010). All of the EO-producing plant families
are rich in terpenoids. At the same time, plant families, such as Apiaceae
(Umbelliferae), Lamiaceae, Myrtaceae, Piperaceae, and Rutaceae, more
frequently contain phenylpropanoids (Chami et al., 2004).
EOs can be obtained from many different parts of plants, including flowers (rose),
leaves (peppermint), fruits (lemon), seeds (fennel), grasses (lemongrass), roots
(vetiver), rhizomes (ginger), wood (cedar), bark (cinnamon), gum (frankincense),
tree blossoms (ylang–ylang), bulbs (garlic), and dried flower buds (clove)
(Tisserand and Young, 2013).
Essential oils are produced by various differentiated structures, especially
the number and characteristics of which are highly variable. Essential oils are
localized in the cytoplasm of certain plant cell secretions, which lies in one or
more organs of the plant; namely, the secretory hairs or trichomes, epidermal
cells, internal secretory cells, and the secretory pockets. These oils are complex
mixtures that may contain over 300 different compounds. They consist of organic
volatile compounds, generally of low molecular weight below 300. Their vapor
pressure at atmospheric pressure and at room temperature is sufficiently high so
that they are found partly in the vapor state. These volatile compounds belong to
various chemical classes: alcohols, ethers or oxides, aldehydes, ketones, esters,
amines, amides, phenols, heterocycles, and mainly the terpenes.
Taxonomy of Essential Oil–Producing Plants
Chemistry of Essential oils
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Alcohols, aldehydes, and ketones offer a wide variety of aromatic notes, such as
fruity ((E)-nerolidol), floral (Linalool), citrus (Limonene), herbal (γ-selinene),
etc.
Furthermore, essential oil components belong mainly to the vast majority of the
terpene family (Figure 1). Many thousands of compounds belonging to the family
of terpenes have so far been identified in essential oils,such as functionalized
derivatives of alcohols (geraniol, α-bisabolol), ketones (menthone, p-vetivone) of
aldehydes (citronellal, sinensal), esters (γ-tepinyl acetate, cedryl acetate), and
phenols (thymol).
Figure 1: Structures of some terpenes
Essential oils also contain non-terpenic compounds biogenerated by the
phenylpropanoids pathway, such as eugenol, cinnamaldehyde, and safrole.
Biogenetically, terpenoids and phenylpropanoids have different primary
metabolic precursors and are generated through different biosynthetic routes
(Figure 2). The pathways involved in terpenoids are the mevalonate and
mevalonate-independent (deoxyxylulose phosphate) pathways, whereas
phenylpropanoids originate through the shikimate pathway.
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Some authors have reviewed the biosynthetic pathways of terpenoids and
phenylpropanoids, respectively, the enzymes and enzyme mechanisms involved,
and information about genes encoding for these enzymes.
CHAPTER THREE
Figure 2: Biosynthesis pathways of monoterpenes and sesquiterpenes
Essential oils have a very high variability of their composition, both in qualitative
and quantitative terms. Various factors are responsible for this variability and can
be grouped into two categories:
• Intrinsic factors related to the plant, and interaction with the environment
(soil type and climate, etc.) and the maturity of the plant concerned, even
at harvest time during the day,
• Extrinsic factors related to the extraction method and the environment.
The factors that determine essential oil yield and composition are numerous. In
some cases, it is difficult to isolate these factors from each other as they are
interrelated and influence each other. These parameters include the seasonal
variations, plant organ, and degree of maturity of the plant, geographic origin, and
genetics.
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Several techniques are used for the trapping of volatiles from aromatic plants. The
most often used device is the circulatory distillation apparatus described by
Cocking and Middleton 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 end of the distillation process, the essential oil is separated from the
water phase for further investigations. The length of distillation depends on the
plant material to be investigated. It is usually fixed to 3–4 h.
A further improvement was the development of a simultaneous distillation–
solvent extraction device by Likens and Nickerson in 1964.The device permits
continuous concentration of volatiles during hydro distillation in one step using a
closed-circuit distillation system.
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CHAPTER THREE
3. Gas chromatography
Gas chromatography (GC) is an analytical technique used to separate
the chemical components of a sample mixture and then detect them to
determine their presence or absence and/or how much is present. These
chemical components are usually organic molecules or gases. For GC to be
successful in their analysis, these components need to be volatile, usually
with a molecular weight below 1250 Da, and thermally stable so they don’t
degrade in the GC system. GC is a widely used technique across most
industries: for quality control in the manufacture of many products from cars
to chemicals to pharmaceuticals; for research purposes from the analysis of
meteorites to natural products; and for safety from environmental to food to
forensics. Gas chromatographs are frequently hyphenated to mass
spectrometers (GC-MS) to enable the identification of the chemical
As the name implies, GC uses a carrier gas in the separation, this plays
the part of the mobile phase (Figure 1 (1)). The carrier gas transports the
sample molecules through the GC system, ideally without reacting with the
sample or damaging the instrument components.
The sample is first introduced into the gas chromatograph (GC), either with
a syringe or transferred from an auto sampler (Figure 1 (2)) that may also
extract the chemical components from solid or liquid sample matrices. The
sample is injected into the GC inlet (Figure 1 (3)) through a septum which
enables the injection of the sample mixture without losing the mobile phase.
Connected to the inlet is the analytical column (Figure 1 (4)), a long (10 –
150 m), narrow (0.1 – 0.53 mm internal diameter) fused silica or metal tube
which contains the stationary phase coated on the inside walls.
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The analytical column is held in the column oven which is heated during the
analysis to elute the less volatile components. The outlet of the column is
inserted into the detector (Figure 1 (5)) which responds to the chemical
components eluting from the column to produce a signal. The signal is
recorded by the acquisition software on a computer to produce a
chromatogram (Figure 1 (6)).
Figure 3: A simplified diagram of a gas chromatograph showing: (1) carrier gas, (2)
autosampler, (3) inlet, (4) analytical column, (5) detector and (6) PC. Credit: Anthias
After injection into the GC inlet, the chemical components of the
sample mixture are first vaporized, if they aren’t already in the gas phase.
For low concentration samples the whole vapor cloud is transferred into the
analytical column by the carrier gas in what is known as splitless mode. For
high concentration samples only a portion of the sample is transferred to the
analytical column in split mode, the remainder is flushed from the system
through the split line to prevent overloading of the analytical column.
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Once in the analytical column, the sample components are separated by
their different interactions with the stationary phase. Therefore, when
selecting the type of column to use, the volatility and functional groups of
the analyses should be considered to match them to the stationary phase.
Liquid stationary phases mainly fall into two types: polyethylene glycol
(PEG) or polydimethylsiloxane (PDMS) based, the latter with varying
percentages of dimethyl, diphenyl or mid-polar functional groups, for
example cyan propyl phenyl. Like separates like, therefore non-polar
columns with dimethyl or a low percentage of diphenyl are good for
separating non-polar analyses. Those molecules capable of π-π interactions
can be separated on stationary phases containing phenyl groups. Those
capable of hydrogen bonding, for example acids and alcohols, are best
separated with PEG columns, unless they have undergone derivatization to
make them less polar.
The final step is the detection of the analytic molecules when they
elute from the column. There are many types of GC detectors, for example:
those that respond to C-H bonds like the flame ionization detector (FID);
those that respond to specific elements for example sulfur, nitrogen or
phosphorus; and those that respond to specific properties of the molecule,
like the ability to capture an electron, as is used with the electron capture
detector (ECD).
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3.1 Principle of GC-MS
Gas chromatography-mass spectroscopy (GC-MS) is one of the so-
called hyphenated analytical techniques. As the name implies, it is
actually two techniques that are combined to form a single method of
analyzing mixtures of chemicals. Gas chromatography separates the
components of a mixture and mass spectroscopy characterizes each of
the components individually. By combining the two techniques, an
analytical chemist can both qualitatively and quantitatively evaluate a
solution containing a number of chemicals.
The Gas Chromatography/Mass Spectrometry (GC/MS) instrument
separates chemical mixtures (the GC component) and identifies the
components at a molecular level (the MS component). It is one of the
most accurate tools for analyzing environmental samples. The GC works
on the principle that a mixture will separate into individual substances
when heated. The sample is injected into the GC inlet where it is
vaporized and swept into a chromatographic column by the carrier gas
(helium). The sample flows through the column and the compounds
comprising the mixture of interest are separated by virtue of their relative
interaction with the coating of the column (stationary phase) and the
carrier gas (mobile phase). The latter part of the column passes through
a heated transfer line and ends at the entrance to ion source where
compounds eluting from the column are converted to ions. A beam of
electrons ionizes the sample molecules resulting in the formation of
molecular ion and smaller ions with characteristic relative abundances
that provide a ‘fingerprint’ for that molecular structure. The mass
analyzer separates the ions and is then detected.
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14 Figure 4: Gas Chromatography/Mass Spectrometry
3.2 Principle of GC-FID
An FID is a common detector used for GC in clinical
laboratories.12,21,22 This type of detector is often used during GC analysis
of ethanol and other volatiles in blood or other aqueous samples. Typical
chromatograms are shown in Fig. 1.10 of volatile compounds that have been
examined by using headspace analysis and a GC system equipped with an
FID. During the operation of an FID, the carrier gas that is leaving the
column is mixed with hydrogen, and the eluting compounds are burned by a
flame that is surrounded by air and an oxygen-rich environment.
Approximately one organic molecule in 10,000 results in the production of
a gas-phase ion. These ions are detected by a collector electrode that is
positioned above the flame. The magnitude of the current that is generated
by these ions is related to the mass of carbon that was delivered to the
detector. This signal can then be used for both the detection and
quantification of organic compounds that are eluting from the column.
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An FID uses a flame to ionize organic compounds containing carbon.
Following separation of the sample in the GC column, each analyte passes
through a flame, fuelled by hydrogen and zero air, which ionises the carbon
atoms.
Once formed, the ions are collected and measured as they create a current
at the detector’s electrodes. The current is produced as the detector collects
the charged ions. The current is then converted to an electrical signal in
picoamperes (pA) or millivolts (mV).
An inert make-up gas is also often used to ensure that additional gas flow is
provided to the sample ions as they move through the detector, which can
improve analytical results. When using a make-up gas, it is important that
the gas used is inert and contains minimal impurities which could interfere
with the sample analysis, risking dampening the signal or increasing the
baseline. Although helium can be used for make-up gas, nitrogen is often
the more cost-effective option, and can be supplied via a nitrogen
gas generator.
Using a gas generator for GC-FID analysis brings convenience and reliability to
the lab. Labs performing analyses such as GC-FID, where multiple gas sources
are required saves lab managers and employees the hassle of coordinating gas
cylinder orders to ensure the gas supply doesn’t run out mid-analysis. Opting for
gas generators for GC-FID can be more cost-effective and is the safest
alternative to cylinders, since gas is generated on-demand to meet instrument
needs, without storage of large volumes of highly pressurized gas.
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Figure 4 : Flame Ionization Detector
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CHAPTER FOUR
4. Determination of essential oils using GC-MS in literature
Daferera, Ziogas, and Polissiou, (2000) isolated essential oils from seven air-
dried plant species were analyzed by gas chromatography−mass spectrometry
(GC-MS). Thymus vulgaris (thyme), Origanum vulgare (oregano), and Origanum
dictamus (dictamus) essential oils were found to be rich in phenolic compounds
representing 65.8, 71.1, and 78.0% of the total oil, respectively. Origanum
majorana (marjoram) oil was constituted of hydrocarbons (42.1%), alcohols
(24.3%), and phenols (14.2%). The essential oil from Lavandula angustifolia
Mill. (lavender) was characterized by the presence of alcohols (58.8%) and esters
(32.7%). Ethers predominated in Rosmarinus officinalis (rosemary) and Salvia
fruticosa (sage) essential oils, constituting 88.9 and 78.0%, respectively.
The essential oils of Piper cernuum and Piper regnellii leaves were analyzed by
gas chromatography-mass spectrometry (GC-MS) and the results were compared
to that obtained by means of a program designed to analyse (13)C-NMR data of
complex mixtures. Bicyclogermacrene (21.88 %)/beta-caryophyllene (20.69 %)
and myrcene (52.60 %)/linalool (15.89 %) were the major constituents in essential
oil from leaves of P. cernuum and P. regnellii, respectively. Both essential oils
presented growth inhibitory activities against Staphylococcus aureus and Candida
albicans (Costantin et al., 2001).
Derwich and co-workers analyzed the chemical composition of essential oils
obtained from Mentha piperita. In their study, the essential oils of Mentha piperita
collected from Atlas median in the region of Meknes (Morocco) were obtained
by hydro-distillation of the aerial parts and analysed by gas chromatography
equipped with flame ionization detector (GC-FID) and gas chromatography
coupled to a mass spectrometry system (GC/MS) for their chemical composition.
Twenty-nine compounds were identified in leaves oil representing 58.61% of the
total oil composition. The yield of essential oil of Mentha piperita was 1.02% and
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the major compound in aerial parts was: Menthone (29.01%), followed by
menthol (5.58%), menthyl acetate (3.34%), menthofuran (3.01%), 1,8-cineole
(2.40%), isomenthone (2.12%), limonene (2.10%), [alpha]-pinene (1.56%),
germacrene-D (1.50%), B-pinene (1.25%), sabinene (1.13%) and pulegone
(1.12%) (Derwich et al., 2010).
Liu and co-authors developed a simple, rapid and solvent-free method based on
gas chromatography–mass spectrometry (GC–MS) following microwave
distillation and headspace solid-phase microextraction (MD–HS-SPME) for the
analysis of the essential oils in two traditional Chinese medicines, Piper nigrum
L. and Piper longum L. Thirty compounds were separated and identified from P.
nigrum L.
The main components were β-caryophyllene (23.49%), 3-carene (22.20%), D-
limonene (18.68%), β-pinene (8.92%) and α-pinene (4.03 %). Forty-five
compounds were separated from P. longum L. and identified. The main
components were β-caryophyllene (33.44%), 3-carene (7.58%), eugenol (7.39%),
D-limonene (6.70%), zingiberene (6.68%) and cubenol (3.64%). To demonstrate
its advantages, MD–HS-SPME was compared to conventional HS-SPME. With
conventional HS-SPME, only 28 and 33 compounds were detected in P. nigrum
L. and P. longum L, respectively. Relative standard deviation (RSD) values of
MD–HS-SPME for the essential oils in P. nigrum L. under optimal conditions
were less than 10%. The results show that microwave distillation has a high
extract efficiency and good precision and can be used to compare similarities and
differences of essential oils (Liu, Song and Hu, 2007).
Artemisia herba alba Asso (Compositae) essential oils, well known in the folk
medicine for antispamodic and bactericidal properties and used in perfumery,
have been widely studied in Morocco, Egypt, Spain, Israel, etc. Plants growing in
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Algeria were very little studied. Consequently, the goal of this work was to
determine the composition of several populations of A. herba alba at different
developmental stages and to compare them with those previously described in
order to find out to which chemotype they belong. Among numerous GC-MS
recorded mass spectra on nonpolar and polar columns, almost one hundred were
identified. The oils are characterized by a high percentage of camphor (19–48%),
1,8-cineole (5–20%), chrysanthenone (5–22.5%), α-thujone (1.0–26.7%), β-
thujone (1.65–9.3%), and camphene (1.7–7.9%). The presence of numerous
chrysanthenyl esters not previously described is worth mentioning. The oils from
Algeria belong to the camphor/thujones/chrysanthenone chemotype (Vernin et
al., 1995).
4.1 Determination of essential oils using GC-FID in literature
Silva-Flores and co-authors isolated essential oils (EO) by hydro distillation in a
Clevenger-type apparatus and characterized by GC-MS and GC-FID analyses.
The major constituents of EO-R. officinalis were camphor (39.46%) and 1,8-
cineole (14.63%), and for EO-L. dentata were 1,8-cineole (68.59%) and β-pinene
(11.53%). A new analytical method based on GC-FID for quantification of free
and encapsulated EO was developed and validated according to ICH. Linearity,
limit of detection and quantification, and intra- and interday precision parameters
were determined.
The methods were linear and precise for the quantification of the main
components of EO. The EO were encapsulated by nanoprecipitation and were
analyzed by the GC-FID method validated for their direct quantification. The NC
size was 200 nm with homogeneous size distribution. The quantification of the
incorporated EO within a NC is an important step in NC characterization. In this
way, an encapsulation efficiency of at least 59.03% and 41.15% of total EO-R.
officinalis and EO-L. dentata, respectively, was obtained. Simple, repeatable, and
reproducible methods were developed as an analytical tool for the simultaneous
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quantification of the main components of EO loaded in polymeric nanocapsules
as well as their monitoring in biological assays (Silva-Flores et al., 2019).
The use of gas chromatography (GC)-mass spectrometry (MS), GC-time-of-flight
MS (TOFMS), comprehensive two-dimensional GC (GC×GC)-flame ionization
detection (FID), and GC×GC-TOFMS is discussed for the characterization of the
eight important representative components, including Z-α-santalol, epi-α-
bisabolol, Z-α-trans-bergamotol, epi-β-santalol, Z-β-santalol, E,E-farnesol, Z-
nuciferol, and Z-lanceol, in the oil of west Australian sandalwood (Santalum
spicatum). S
ingle-column GC-MS lacks the resolving power to separate all of the listed
components as pure peaks and allow precise analytical measurement of individual
component abundances. With enhanced peak resolution capabilities in GC×GC,
these components are sufficiently well resolved to be quantitated using flame
ionization detection, following initial characterization of components by using
GC×GC-TOFMS (Shellie, Marriott, and Morrison, 2004).
The use of direct thermal desorption−gas chromatography−mass spectrometry
(DTD-GC-MS) and DTD-GC−flame ionization detection (DTD-GC-FID) for
characterization of hop essential oils is described. Four hop varieties (Nugget,
Galena, Willamette, and Cluster) from the Yakima valley (Yakima, WA) 1998
harvest were analyzed by DTD-GC-MS and DTD-GC-FID methodology.
Approximately 1 g of hops was needed for the analysis. Hop samples were
prepared for GC-MS and/or GC-FID profiling in ∼20 min. More than 100 volatile
compounds have been identified and quantified for each hop variety.
The results were found to be in good agreement with conventional steam
distillation−extraction (SDE) data. A calibration curve for determination of
essential oil content in hops by DTD-GC-FID has been generated. Quantitation
of hop oil content by DTD-GC-FID was shown to be in good agreement with
conventional SDE data. The recovery of key oil components valuable for varietal
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identification was demonstrated to be highly reproducible and characteristic of
each variety analyzed when DTD-GC-FID was used for analysis (Eri et al., 2000).
Rather and co-workers analysed the leaf volatile constituents of the essential oils
of Artemisia indica Willd. and Artemisia vestita Wall using a combination of
capillary GC–FID, GC–MS and FT-IR (Fourier-Transform Infra-Red) analytical
techniques. The analysis led to the identification of 42 compounds in the essential
oil of A. indica, representing 96.6% of the essential oil and the major components
were found to be artemisia ketone (42.1%), germacrene D (8.6%), borneol (6.1%)
and cis-chrysanthenyl acetate (4.8%).
The essential oil was dominated by the presence of oxygenated monoterpenes
constituting 65.2% of the total oil composition followed by sesquiterpene
hydrocarbons and monoterpene hydrocarbons constituting 15.7% and 10.7%,
respectively of the total oil composition.
The essential oil composition of A. vestita was found to contain a total of 18
components representing 94.2% of the total oil composition. The principal
components were found to be 1,8-cineole (46.8%), (E)-citral (13.7%), limonene
(9.8%), α-phellandrene (6.4%), camphor (5.0%), (Z) and (E)-thujones (3.0%
each). Oxygenated monoterpenes were the dominant group of terpenes in the
essential oil constituting 73.1% of the total oil composition followed by
monoterpene hydrocarbons (17.3%). The results of the current study reveal
remarkable differences in the essential oil compositions of these two Artemisia
species already reported in the literature from other parts of the globe (Rather et
al., 2017).
Essential oils obtained by hydrodistillation from leaves and spikes of Piper
lanceaefolium H.B.K. of Costa Rica were analysed by GC-FID, GC-MS and 13C-
NMR methods. Main constituents found in the oil from leaves were sesquiterpene
hydrocarbons especially β-caryophyllene and germacrene D and
phenylpropanoids, of which elemicin and parsley apiol were the major ones. The
volatile oil from spikes showed monoterpene hydrocarbons, namely α- and β-
pinene, and the same phenylpropanoids as in the oil from leaves as the major
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constituents. Results obtained in the analysis by GC-FID and GC-MS of the
essential oils from individual plants of different geographic origin were submitted
to chemometric cluster analysis and principal component analysis, showing the
presence of three different types of oils (i) parsley apiol/elemicin, (ii)
elemicin/parsley apiol/dill apiol, and (iii) parsley apiol/dill apiol (Mandina et al.,
2001).
CONCLUSION
GC-MS can perform much more reliable qualitative and quantitative analysis
of complex essential oils samples. Meanwhile, GC-FID eventually was a
very basic chromatograph technique, but provides us more information on
retention indices that are crucial in analytical chemistry. In general, GC
coupled with MS or FID are the most suitable and widely analytical methods
used in essential oils analysis. These techniques can be used to identify a
group of essential oils components simultaneously in variety plant extracts.
Many essential oils in different plant sources have been extracted, analyzed
and identified with appreciable accuracy and precision. GC-MS and GC-
FID found to be important methods for analyzing essential oils.
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