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

I

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.

II

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: / /

III

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

IV

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

1

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).

2

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.

3

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.

4

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

5

9

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

6

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.

7

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.

8

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.

9

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.

10

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.

11

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).

12

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.

13

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.

14

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.

15

Figure 4 : Flame Ionization Detector

16

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

17

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

18

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

19

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

20

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

21

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.

22

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