paper 2

IInntteerrnnaattiioonnaall JJoouurrnnaall ooff CChheemmiiccaall aanndd
NNaattuurraall SScciieennccee
Vol. 3, No. 1 (2015): 195-199
Review Article
Open Access ISSN: 2347-6672
Developing a Method for Trace Metal Analysis in
Spices using Spectroscopic Techniques: A Review
Kassa Belay1
* and Zebib Abisa2
1
Department of Chemistry, College of Natural and computational sciences, Adigrat University
2
Department of Animal Science and technology, College of Agriculture, Adigrat University
* Corresponding author: Kassa Belay; email: kassa.belay1@gmail.com
ABSTRACT
The review assesses levels of the toxic heavy metals Cd , Pb, Cr, Hg and Fe in different spices species found in local
market in Ethiopia. Heavy metal refers to any metallic chemical element that has a relatively high density and is
toxic or poisonous at low concentrations. Examples of heavy metals includes: Mercury (Hg), Cadmium (Cd), Arsenic
(As), Chromium (Cr), Thallium (Tl) and lead. Spice is a dried seed, fruit, root, bark or flower of a plant or a herb used
in small quantities for flavor, color or as a preservative. The most commonly used methods for the sample treatment
of spices are Dry ashing, Wet digestion and Microwave assisted treatment. Microwave digestion is simple, rapid and
reliable for the digestion of a variety of sample matrices.
Keywords: Trace metals, spectroscopy.
1.0 INTRODUCTION
The term heavy metal refers to any metallic chemical
element that has a relatively high density and is toxic or
poisonous at low concentrations. Examples of heavy
metals includes: Mercury (Hg), Cadmium (Cd), Arsenic
(As), Chromium (Cr) ,Thallium (Tl) and lead . Heavy
metals are natural components of the Earth's crust [6].
To a small extent they enter our bodies via food,
drinking water and air. As trace elements, some heavy
metals (e.g. copper, selenium, zinc) are essential to
maintain the metabolism of the human body. However,
at higher concentrations they can lead to poisoning.
Heavy metal poisoning could result from drinking-
water contamination, high ambient air concentrations
near emission sources, or intake via the food chain
[18].
Heavy metals are dangerous because they tend to
Bioaccumulate. Bioaccumulation means an increase in
the concentration of a chemical in a biological organism
over time, compared to the chemical's concentration in
the environment [27]. Heavy metals are those with
atomic weights from 63.546 to 200.59 [11], and specific
weight higher than 4. These metals may reach and
contaminate plants, vegetables, fruits and canned foods
through air, water, and soil during cultivation and also
during industrial processing and packaging.
Trace heavy metals are important in daily diets,
because of their essential nutritious value and possible
harmful effects. Metals like iron, copper, zinc, cobalt
and manganese are essential metals since they play an
important role in biological systems; whereas mercury,
lead, cadmium, etc. are non-essential metals which can
be toxic even in trace amounts [11].
Heavy or trace metals play positive and negative roles
in human life [1]. Some of the heavy metals such as iron
(Fe), zinc (Zn) and copper (Cu) are considered essential
but they can become harmful above certain levels.
Some metals like cadmium (Cd), lead (Pb) and mercury
(Hg) have toxic roles in biochemical reactions in our
body. Zinc is important during puberty, pregnancy, and
menopause. If large doses of zinc (10-15 times higher
than the recommended daily intake) which is 8-15
mg/day are consumed, stomach cramps, nausea, and
vomiting may occur. Ingesting high levels of zinc for
several months may cause anaemia, damage the
pancreas, and decrease levels of high-density
Received: 29 November 2014 Accepted: 17 December 2014 Online: 02 January 2015
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Kassa Belay et al. / Int J Chem Natur Sci. 2015, 3(1): 195-199
lipoprotein (HDL) cholesterol. Consuming low levels of
zinc is at least as important a health problem as
consuming too much zinc. Without enough zinc in the
diet, people may experience loss of appetite, decreased
sense of taste and smell, decreased immune function,
slow wound healing, and skin sores. Too little zinc in
the diet may also cause poorly developed sex organs
and retarded growth in young men. If a pregnant
woman does not get enough zinc, her babies may have
birth defects [5].
The aim of this review is to see the efficiency of
Microwave, Wet Ashing and Dry Ashing digestion
methods on determination of some selected heavy
metals in spice sample produced in Ethiopia using AAS.
A spice is a dried seed, fruit, root, bark or flower of a
plant or a herb used in small quantities for flavor, color
or as a preservative. Many of these substances are also
used in traditional medicines. Globalization has made
these spices easily available, and increasing their
popularity. This chapter reviews the traditional uses of
selected spices.
2.0 SPICES IN ETHIOPIA
In Ethiopia, there are between 6,000 and 7,000 higher
plant species, out of about 500 (about 8%) are edible.
According to [4], about 400 of these are wild or semi-
wild edible plants, while 25% (over 100) are cultivated
edible plants. Most Ethiopian spices are cultivated.
They comprise about 12% (16 out of 127) of food crops
grown in home gardens. In a study of 203 edible wild
or semi-wild plant species, Tadesse and Asfaw list 11 as
spices, condiments or flavoring plants [4].
A 1991 study of 50 spices, aromatic and medicinal
plants in eastern Ethiopia indicated that a sizable
number of local merchants were involved in the trade
of spices, along with other aromatic and medicinal
plants. A significant number of the plants (over 25)
were spices. Interestingly enough, some of the spices
were either imported or smuggled from Asia or East
African countries. For example, spice plants such as
Cinnamomum zeylanicum (qarafa), Elettaria
cardamomum (heil), Piper longum (timiz), and Piper
nigrum (qundo berbere) fall into this category.
The study further indicated that capsicum (berbere), an
Allium species (shinkurt), and turmeric (ird) were the
most common spices found in all local markets,
witheach market in turn specializing in selling certain
spices. For example, the markets in Dire Dawa and
Harar were found to sell more of fenugreek (abish),
Foeniculum vulgare (ensilal) and coriander (dimbelal),
whereas the Jimma-Aggaro markets specialized in
selling cardamom (korarima), ginger (jinjibil) and garlic
(netch shinkurt). On the other hand, in Hosahina
market, fenugreek (abish), caraway (netch azmud),
garlic (netch shinkurt), and coriander (dimbilal) were
more common. The authors attribute the
predominance of one spice over the other to mainly the
food habits, economy and ecology of the respective
areas that the markets cater to [13].
2.1. FENUGREEK
Fenugreek (Trigonella foenum-graecum) is commonly
known as maithray (Bangla, Gujarati), methi or mithi in
Hindi, menthyada soppu (Kannada), ventayam (Tamil),
menthulu (Telugu), hilbeh (Arabic), ulluva (Malayalam)
and shambalîleh (Persian). The name “fenugreek” or
foenum-graecum is from Latin for “Greek hay.” In
traditional medicines it is used as an aphrodisiac,
astringent, demulcent, carminative, stomachic, diuretic,
emmenagogue, emollient, expectorant, lactogogue,
restorative, and tonic.
[8] Fenugreek is used for a variety of health conditions,
including digestive problems, bronchitis, tuberculosis,
fevers, sore throats, wounds, arthritis, abscesses,
swollen glands, skin irritations, diabetes, loss of
appetite, ulcers and menopausal symptoms, as well as
in the treatment of cancer. An infusion of the leaves is
used as a gargle for recurrent mouth ulcers. As an
emollient it is used in poultices for boils, cysts and
other complaints. It is used to reduce blood sugar level
and to lower blood pressure. Fenugreek has been
demonstrated to relieve congestion, reduce
inflammation and fight infection. Fenugreek is used for
treating sinus and lung congestion, and loosens and
removes excess mucus and phlegm. The Chinese use
the seed for abdominal pain, chilblains, cholecytosis,
fever, hernia, impotence, hypogastrosis, nephrosis, and
rheumatism [8].
2.2. GARLIC
Garlic (Allium sativum L.) is a species in the onion
family, Alliaceae. One of the oldest dietary vegetables, it
has been used as early as 3000 BC for the treatment of
intestinal disorders and is now known for its
fibrinolytic activity and its possible role in lowering
blood cholesterol.27 Dietary patterns in the
Mediterranean characterized by high consumption of
fruits and vegetables, especially garlic, are believed to
be beneficial to the regional patterns of atherosclerotic
disease [10]. The spice has also been used in folk
medicine for the treatment of diabetes and
inflammation. A well-known remedy for local pain is to
crush garlic bulbs, apply the crushed garlic to the site of
pain and then put a bandage over it. This practice is
done by “naturopathic physicians” worldwide and as
part of traditional “Arabic Medicine” in the Middle East.
In Nepal, East Asia and the Middle East it has been used
to treat all manner of illnesses including fevers,
diabetes, rheumatism, intestinal worms, colic,
flatulence, dysentery, liver disorders, tuberculosis,
facial paralysis, high blood pressure and bronchitis. In
Ayurvedic and Siddha medicine garlic juice has been
used to alleviate sinus problems. In Unani medicine, an
extract prepared from the dried bulb is inhaled to
promote abortion or taken to regulate menstruation.
Unani physicians also use garlic to treat paralysis,
forgetfulness, tremor, colic pains, internal ulcers and
fevers [3].
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2.3. GINGER
Ginger (Zingiber officinale) is commonly used as a
cooking spice throughout the world. It is also known as
zanjabil (Arabic), aadu (gujarati), shunti (Kannada),
allam (Telugu), inji (Tamil and Malayalam), alay
(Marathi), aduwa (Nepali), and adrak (Hindi and Urdu).
The rhizome of ginger has long been used in traditional
Chinese medicine to treat a wide range of ailments
including gastrointestinal disorders, mainly nausea and
vomiting associated with motion sickness and
pregnancy, abdominal spasm, as well as respiratory
and rheumatic disorders [2].
Ginger is widely used for dyspepsia, flatulence,
abdominal discomfort and nausea. It has been
recommended by herbalists for use as a carminative
(an agent that reduces flatulence and expels gas from
the intestines), diaphoretic (an agent that produces or
increases perspiration), antispasmodic, expectorant,
peripheral circulatory stimulant, and astringent (an
agent that causes shrinkage of mucous membranes or
exposed tissues and that is often used internally to
check discharge of blood serum or mucous secretions)
[26].
Ginger has a reputation for its anti-inflammatory
properties. In traditional medicine, ginger has been
used to treat a wide array of ailments including sore
throats, stomachaches, diarrhea, toothache, gingivitis,
arthritis (inflammation of the joints), bronchitis (an
acute inflammation of the air passages within the
lungs), muscle pains, sprains, constipation dermatitis,
hypertension, dementia, fever, infectious diseases,
helminthiasis, stroke, constipation, diabetes and
asthmatic respiratory disorders [17].
2.4. KALONJI
Kalonji (Nigella sativa) is an annual flowering plant,
native to southwest Asia. The scientific name is a
derivative of Latin niger meaning “black.” In English,
Nigella sativa seed is variously called black cumin,
fennel flower, nutmeg flower, Roman coriander,
blackseed, black caraway, or black onion seed. In
English-speaking countries with large immigrant
populations, it is also known as kalonji (Hindi), kezah
(Hebrew), chernushka (Russian), çörek otu (Turkish),
habbat albarakah (Arabic “seed of blessing”) or siyah
daneh (Persian). It is regarded as an aromatic,
carminative, diaphoretic, digestive, diuretic,
emmenagogue, excitant, lactagogue, laxative,
expectorant, antipyretic, antihelminthic, resolvent,
stimulant, sudorific, parasiticide, stomachic, tonic, and
vermifuge.
Prophet Muhammad (SAW) once stated that the black
seed can heal every disease except death. [9] In
Ayurvedic medicine, it is used as purgative adjunct. In
Unani, it is considered an abortifacient and a diuretic
and is used for ascites, coughs, eye-sores, hydrophobia,
jaundice, paralysis, piles and tertian fever. The
Lebanese take the seed extract for liver ailments. In
Indonesia, the seeds are added to astringent medicines
for abdominal disorders. In Malaya, the seeds are
poulticed to treat abscesses, headaches, nasal ulcers,
orchitis, and rheumatism. Arabian women use the
seeds as a galactagogue. [9] Kalonji seeds and oil, alone
or in combination with other drugs, are highly effective
in alopecia, vitiligo and other skin ailments. Continuous
use of kalonji is effective in mad dog bites. It is useful in
paralysis, facial palsy, migraine, amnesia and
palpitation. Its powder if taken with water is effective
in treating hemorrhoids.
If Kalonji seeds are boiled in vinegar and this solution
is applied to the gums and teeth, it can reduce
inflammation of the gums and also relieve pain. It has
been reported that in a fine powder form it is effective
if applied in early stages of cataract. Black seed oil has
been a women’s beauty secret since ancient times.
Black cumin and its oil have been used to purge
parasites and worms, detoxify, ameliorate amebic
dysentery, shigellosis, abscesses, old tumors, ulcers of
the mouth, and rhinitis. For external use, the seed is
ground into a powder and mixed with sesame oil, and
can be used to treat abscesses, hemorrhoids and
orchitis. Finally, the powdered seed has been used to
remove lice from the hair [22].
There are many reasons for which people use spices,
though, taste probably tops the list. There are several
spices that simply smell good and those smells can be
alternately soothing or exciting. Some of the types of
spices include Onion, Ginger, Garlic, Cloves, Dawadawa,
Cinnamon, Rosemary, Thyme, Marjoram, Pepper, Black
Pepper, olive, Lime, Anise, Nutmeg, Curry, Almond,
Turmeric, Oregano, Sage, Lemon balm, Peppermint,
Dill, and Coriander. Over the centuries, certain spices
have been said to heal every infection, disease and
malady known to man. But there is no doubt that spices
do have value far beyond enhancing the taste of food.
However, besides adding to the taste, spices have
multifarious functions that include combating
foodborne microorganisms, reducing food poisoning,
[24] antioxidant function, (Pokorney, 1991) and
antimicrobial activity [23]. Spices are also known to
possess a wide range of medicinal values. Such values
include fight against cancer causing cells, reduction of
cholesterol level in the blood and prevention of several
skin diseases [25].
3.0 METHODS FOR THE DETERMINATION
OF TRACE ELEMENTS
Accuracy and precision are the two most important
analytical figures of merit for trace element
determination in biological materials. In many
applications the methods need to be suitable for
automation and routine applications and the sample
consumption should be as low as possible [12]. Atomic
absorption techniques (AAS) using flame (FAAS),
electrothermal atomic absorption spectrometry
(ETAAS), atomic fluorescence spectrometry (AFS) and
inductively coupled plasma techniques (ICP) are the
most commonly used techniques by the greatest

number of researchers for trace element determination
in seasoning products.
3.1. Sample Treatment
Sample treatment is an important step in order to
separate the analyte from the matrix and to avoid
organic matter which may react with the metal ions or
chemical reagents and interfere with the analyte during
measurements.
The most commonly used methods for the sample
treatment of spices are
(1) Dry ashing,
(2) Wet digestion,
(3) Microwave assisted treatment (Hoeing, 2001)
3.1.1. Dry Ashing
Dry ashing; programmable furnaces may be used for
this purpose. The commonly applied temperature is
around 450 0C. Fresh or dried samples are weighed in
suitable crucibles and placed in the furnace.
Temperature is elevated up to 450 0C following a
heating programme. The resulting inorganic residue
known as ash is dissolved in a suitable acid to obtain a
solution to be analyzed. Results are expressed on fresh
or dry weight depending on the initial condition [15].
Dry ashing offers the advantage of complete
elimination of the organic matter leading to high pre-
concentration factors. However it suffers from possible
losses of volatile analytes such as As, Se, Cd and Hg,
analyte reactions with the crucible material and sample
contamination from combustion residues [16].
3.1.2. Wet Digestion
Wet digestion is performed by using concentrated acids
including nitric acid, perchloric acid, hydrogen
peroxide and mixture of acids in open or closed vessels.
Incomplete digestion of the matrix is a common
problem. In such a case the mixture of sulphuric,
perchloric or nitric acids is one of the best means to
dissolve organic components. For plant species
including varying amounts of silicates, hydrogen
fluoride is used for complete digestion [20].
3.1.3. Microwave (MW)-Assisted Treatment
Nowadays microwave heating is the most commonly
used technique for treatment of a variety of samples. It
has proved to be the most suitable digestion method
for complex matrices including oxides, silicates and
organic substances. It decreases digestion times,
increases analyte recoveries also for volatile elements
and reduces cross contamination and consumption of
reagents leading to improvement in detection limits
and overall accuracy of analysis the major advantage of
this system is its high heating efficiency [14].
Table 1: Some common heavy metals in spices in soudi Arabia [28].
Rol No. Spices Cd μg/g Pb
μg/g
Cr
μg/g
Hg
μg/g
Fe
μg/g
1 Ginger 0.362 0.39 0.03 0.004 134.384
2 Garlic 0.642 0.53 0.04 0.003 124.034
3 Fenugreek/Methi 0.090 0.059  0.020
4 Onion 0.800 0.44 0.05 0.004 146.880
4.0 CONCLUSION
In this review the analysis of a variety of spices
including Garlic, Fenugreek, Ginger and onion were
performed by using Atomic Absorption spectrometry
for Pb, Cr, Cd, Hg and Fe determination.
The review assesses levels of the toxic heavy metals Cd
and Pb, Cr, Hg and Fe in different spices species found
in local market in Ethiopia. The results showed the
ability of these plants to accumulate relatively higher
amounts of Fe among the determined metals. Heavy
metals Cr and Hg were found to be comparatively at
lower levels in most of the spices. Microwave digestion
is simple, rapid and reliable for the digestion of a
variety of sample matrices [21].
5.0 RECOMMENDATION
The following recommendations are suggested as a
result of the outcome of this study
 Spices should be directly sampled from the
areas of cultivation.
 This study should be repeated with ICP-OES to
check the exact heavy metal contents of the
selected spices.
 Monitoring of the levels of heavy metals in spices
should be encouraged.
 In different digestion methods should be proceed
The extract (acids) ant
The digestion methods (kjldhade).
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*****
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