Available online at www.sciencedirect.com
APCBEE Procedia 2 (2012) 135 – 140
ICBF FS 2012: Appril 7-8, 2012, Bangkok, Thailandd
Appliccation off Atomicc Absorpption Speectroscoopy in Foood Sciencees: (A Sttudy on Cucurbiita Maxima) V Vishal Mahhabira and Vishwa V Veermab ∗ b
a Chemistry Division, University off Guyana, Berbicce Campus,Berbicce, Guyana, Southh America D Department of Chhemistry, Facultyy of Natural Sciennces, University of o Guyana,Turkeyyen Campus, Pin Code 101110, Georgetown, Guyana, South America
Absttract The study of this research is basedd on the determiination of multii-trace elementss in cucurbita maxima m (pumpkkin) by Flame mic Absorption Spectrophotom metry. The elem ments, K, Ca, Mg, M P, Zn, Cu,, Ni, Fe, Co, annd heavy metalls, Pb and Cd Atom weree determined inn the seed, pulpp and skin (peeel) of three pum mpkins, one frrom each of thee three countiees of Guyana. Therre was a significcant difference in the means foor each of the elements of interrest. There was no significantt difference in the means m of each element e in the seed s for the Beerbice, Essequibbo and the Dem merara pumpkinns, likewise forr the pulp and skin samples. In terrm of the distribution of the ellements in the different d parts of o the pumpkinn, it was found tthat there was a significant difference in the meanns for each elem ment. They werre in higher quaantities in the seeed than in the skin and pulp sampples, respectivelly. The results show some eleements essentiaal to the human diet such as K, K Cu, Zn, P, Fe are abundant in the seeds of the pumpkins, p impllying that the nutritive n value of o pumpkin seeds is high. Traaces of all the eelements were foundd in the skin samples, justifyinng some of the use u of pumpkinn skin, such as, as an ingrediennt in skin cream ms. The heavy metaals cadmium annd lead were preesent with the latter l only beinng found in the skin samples, making it harm mful as a food sincee lead is toxic at a even small leevels. The Caddmium levels were w the more siignificant of thee two, suggestinng significant polluution of the soills and water arround the areas of production of the crop. However, H at levvels below 0.500 ppm it helps preveent growth of prostate p cancer cells c in human beings. b
© B.V. and/or peerpeer review responsibility of Asia-Pacifi c fic ©2012 20012Published PublisheddbybyElsevier Elsevier B Selection B.V. Selection n and/or r under review under responsibility y of Asia-Pacif Chemical, Engineering Society Open access under CC BY-NC-ND license. Chem mical,Biological Biological&&Environmental Enviroonmental Engiineering Socieety Keyw words: AAS, Cucuurbita Maxima, Metals M Analysis
1. In ntroduction
∗
auuthor, Tel: +5922-2226690, Faxx: +592-22266991 C Corresponding E-mail address :
[email protected]
2212-6708 © 2012 Published by Elsevier B.V. Selection and/or peer review under responsibility of Asia-Pacific Chemical, Biological & Environmental Engineering Society Open access under CC BY-NC-ND license. doi:10.1016/j.apcbee.2012.06.025
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Cucurbita maxima var. maxima Duchesne, commonly called pumpkin is an orange fruit from the Cucurbita genus that belongs to the Cucurbitaceae family; which also includes squash and cucumbers. The pumpkin consists of many parts out of which three are basic; the skin, pulp and the seeds. The pumpkin pulp and seeds are known sources of treatment for various health problems such as: decreasing cancer risks, antiinflammatory, improve bone density and prostate health in elderly men, anti oxidative, prevent kidney stones, combating depression, and to deter intestinal parasites such as tapeworms etc. [1]. Minerals play an important role in chemical, biological, biochemical, metabolic, catabolic and enzymatic reactions in the living cells of plants, animals and human beings and they have great significance due to their tendency to accumulate in the vital human organs over prolonged periods of time. Apart from hydrogen, carbon, oxygen, nitrogen and sulphur which are the bulk of living matter, there are essential minerals which are vital in the functioning of the human body. A mineral is an element which is needed in an amount of more than 100 mg per day like sodium, potassium, magnesium, phosphorous, chlorine, sulphur and calcium and they are referred to as macro minerals. Those elements which are essential but are needed in amounts less than 100 mg per day are known as trace elements which include: iodine, iron, copper, manganese, zinc, cobalt, molybdenum, selenium and chromium [2, 5]. An element is essential when a deficient intake consistently results in an impairment of a function from optimal to suboptimal and when supplementation with physiological levels of this element, but not of others, prevents or cures this impairment [3]. Among the trace elements include the heavy metals like lead, mercury, cadmium, which may disturb the normal functions of the central nervous system, liver, lungs, heart, kidney; resulting in conditions such as hypertension, abdominal pain, skin eruptions, intestinal ulcer and different types of cancer, if they enter the body. The main aim of this study is to investigate the levels of some macro minerals and trace elements in the seeds, pulp and skin of pumpkin. A study was done by Durdana Rais Hashmi, Shahnaz Ismail and G.H. Shaikhto assess the level of Fe, Cu, Mn, Zn, and Cr in 18 varieties of vegetables. [4]. However, the research did not indicate the part of the vegetable which was analysed. 2. Experimental Details: An Atomic Absorption Spectrophotometry (AAS) was used for the determination of K, Ca, Mg, Cu, Fe, Zn, Co, Ni, Cd and Pb. This technique is based on digesting the sample by oxidising the organic matter composition and aspirating (converting the digested sample into a liquid/gas aerosol) the treated sample into a characteristic flame. Atomic Absorption Spectrophotometer (Perkin Elmer-3030B), equipped with a graphite furnace was used [3]. 3. Open Vessel Wet Digestion The aim of the digestion was to solubilise the elements of interest in the pumpkin samples. The digestion process is a combination of oxidation/destruction of organic matter and dissolution of the mineral phase to a certain extent to bring the elements into solution. In the procedure, samples were treated with a mixture of concentrated nitric acid and hydrochloric acid. This formed nitrohydrochloric acid (NOCl), according to equation 1, which had a strong oxidizing effect and gave almost complete dissolution of organic samples. The NOCl destroyed the organic matter to give carbon dioxide and water. 3 HCl + HNO3
2 H2O + NOCl + Cl2
(1)
Also, as part of the digestion hydrogen peroxide was used. Under acidic conditions hydrogen peroxide undergoes an equilibrium reaction to give hydroxyl radical (equation 2) which aided in oxidation of organic matter.
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Vishal Mahabir and Vishwa Verma / APCBEE Procedia 2 (2012) 135 – 140
H 2O 2 + H +
H2+OOH
H2O + .OH
(2)
The hydrogen peroxide was also added to remove any NOCl that was present. In this technique the liquid sample was aspirated, i.e. aerosolized and mixed with combustible gases such as air acetylene and nitrous oxide acetylene (used for Ca analysis). The mixture was ignited in a flame whose temperature reached from 2100 to 2800ͼC. In the combustion process the atoms of the elements of interest in the sample were reduced to free unexcited ground state atoms which absorbed light at a characteristic wavelength as illustrated in fig. 1 below. The characteristic wavelength of the elements is specific and accurate to 0.01 to 0.10 nm. To provide the element with specific wavelengths, a light beam from a lamp whose cathode is made of the element being determined, was passed through the flame. In addition, the slit widths for each element were set. Then a device such as a photomultiplier would have detected the reduction in the intensity of light due to absorption by the analyte, and this would have been directly related to the concentration of the element in the sample. 4. Determination of Phosphorous in the samples by UV-VIS Spectrophotometry Phosphates themselves are colourless. Due to the reactive nature of phosphates, they are easily converted to a coloured compound through chemical reaction which can then be directly detected. This ammonium vanadomolybdate reagent will react with phosphates to produce a yellow heteropoly acid compound with an uncertain formula (though it is thought to be (NH4)3PO4·NH4VO3·16MoO3.). This compound will absorb UV light at 410nm. Absorbance is directly proportional to concentration of phosphorous. The values of the detected elements are given the following Tables. Table 1. showing mg of each element in 100 Grams of fresh seed from the three counties (Berbice, Essequibo and Demerara refer to three counties in all the places)
mg per 100g Fresh Seed and % DV Element
Berbice
% DV
Essequibo
% DV
Demerara
% DV
Calcium
3.778
0.38
2.339
0.23
3.183
0.32
Iron
3.621
20.12
3.652
20.29
5.639
31.33
Magnesium
1.022
0.26
0.613
0.15
0.979
0.25
Copper
0.428
21.40
0.200
10.00
0.297
14.85
Cadmium
1.737
0.00
1.267
0.00
2.272
0.00
Zinc
3.188
21.25
1.822
12.15
2.778
18.52
Cobalt
0.419
0.00
0.634
0.00
1.744
0.00
Nickel
6.676
0.00
5.168
0.00
5.062
0.00
52.175
5.22
20.440
2.04
26.459
2.65
Potassium
4.469
0.13
4.657
0.13
4.062
0.12
Lead
0.000
0.00
0.000
0.00
0.000
0.00
Phosphorous
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Table 2. showing milligrams of each element in 100 grams of fresh pulp from the three counties
mg per 100g Fresh Pulp and % DV Element
Berbice
% DV
Essequibo
% DV
Demerara
% DV
Calcium
5.738
0.57
0.430
0.04
0.519
0.05
Iron
7.077
39.32
0.693
3.85
1.112
6.18
Magnesium
1.483
0.37
0.120
0.03
0.125
0.03
Copper
0.085
4.25
0.006
0.30
0.007
0.35
Cadmium
1.018
0.00
0.178
0.00
0.280
0.00
Zinc
0.217
1.45
0.022
0.15
0.019
0.13
Cobalt
0.000
0.00
0.000
0.00
0.005
0.00
Nickel
5.201
0.00
0.681
0.00
1.273
0.00
Phosphorous
22.954
2.29
2.241
0.22
2.210
0.22
Potassium
24.594
0.70
2.213
0.06
2.235
0.06
0.000
0.00
0.000
0.00
0.000
0.00
Lead
Table 3. showing milligrams of each element in 100 grams of skin from the three counties
mg per 100g Fresh Skin and % DV Element
Berbice
% DV
Essequibo
% DV
Demerara
% DV
Calcium
1.060
0.11
1.034
0.10
0.760
0.08
Iron
3.070
17.06
2.871
15.95
3.234
17.97
Magnesium
0.508
0.13
0.513
0.13
0.513
0.13
Copper
0.007
0.35
0.011
0.55
0.004
0.20
Cadmium
1.414
0.00
1.459
0.00
1.593
0.00
Zinc
0.020
0.13
0.017
0.11
0.029
0.19
Cobalt
1.242
0.00
1.535
0.00
1.616
0.00
Nickel
3.081
0.00
2.192
0.00
2.182
0.00
Phosphorous
4.999
0.50
5.375
0.54
4.194
0.42
Potassium
4.654
0.13
4.272
0.12
4.530
0.13
Lead
0.136
0.00
0.260
0.00
0.021
0.00
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Distribution of Zinc in the Seed, Pulp and Skin 25
% Daily Value
20 Berbice
15
Essequibo Demerara
10 5 0 Seed
Pulp
Skin Part of Pumpkin
Fig. 1. illustrating the distribution of Zinc in the seed, pulp and skin samples of the three pumpkins
5. Discussion The results obtained in this research showed lower quantities of each element per 100 grams of fresh seed and pulp samples than in literature. For instance, the average amount of Ca in the pulp of the pumpkins studied was found to be 0.475 mg per 100g of fresh pulp, whereas, previous research found 21 mg of Ca per 100 grams of fresh pulp. This was so because of the different types of soil conditions under which the crop was cultivated and the various climatic and weather conditions of the different geographic locations of study from those of literature. However, the results obtained still showed significant levels of iron, copper, zinc and phosphorous in the seed samples (high % DV) and can be compared over the three different geographical areas studied, and with respect to the three different parts of the pumpkin, the seed, pulp and skin. Iron, copper, zinc, phosphorous and potassium were all important elements which were found in quantities that is considered high in term of the % DV of each that the pumpkin seeds can provide.It was found that the elements which are known mineral nutrients, that is, all of the elements analysed for except Cd and Pb, were in larger amounts in the seed than in the skin and pulp, respectively, of each of the pumpkins. The level of cadmium seemed to be threatening since the seed samples contained about 1.27 to 2.27 mg Cd per 100 grams of fresh seed. The pulp contained 0.10 to 0.28 mg Cd per 100 grams of fresh pulp and the skin had about 1.40 to 1.60 mg Cd per 100 grams of fresh skin. However, cadmium is helpful in preventing the growth of prostate cancer cells and a level of < 0.50 ppm is safe for human consumption. Lead was the other heavy metal detected. However, it was found only in the skin samples, but in all three of the pumpkins.
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Acknowledge The initial research work was done in the Department of Chemistry, University of Guyana. However, assistance was provided by other laboratories in the country. Thanks to Ms. Sandrene Abrams and staff at GGMC for their assistance. Special thanks to Randy Sanichar and the staff of the Quality Assurance lab at DDL for accommodating me on their AAS instrument. Thanks also to Kevin and Mr.G. Jafar of GUYSUCO, LBI, and Ms. A. Hinds, Senior Analyst of Food and Drugs Lab, for use of the UV-Vis Spectrophotometer. References [1] http://sennyong.blogspot.com/2010/02/dont-throw-away-pumpkin-skin-and-seeds.html[2] Aggett P. J. Trace Elements in Human Nutrition, Journal of Tropical Paediatrics, April 1980, 61-64. [3] http://www.sciencemag.org/content/213/4514/1332.pdf, pg. 1332. [4] Raish Hashmid D, Ismail S, Shaikh G.H.Assessment of the level of trace metals in commonly edible vegetable locally available in the markets of Karachi City, Centre for environmental studies,PCSIR Laboratories Complex, Pakistan, 2007. [5] Mertz, W. The Essential Trace Elements, AAAS 1981;213:1332-1338.
