Trace Element Levels in Fruits and Vegetable by using Atomic Absorption Spectrophotometer (AAS)

N.V.S. Venugopal*, B. Sumalatha, Syedabano and G. Srinivas

Department of Chemistry, G.I.T, Gitam University, Rushikonda, Visakhpatnam-530045, A.P, India.

*Corresponding Author E-mail: venu7000@gmail.com

ABSTRACT:

Different trace metals levels [Nickel, palladium, cadmium, zinc, copper, iron] were determined in various vegetables such as cabbage, carrot, onion, tomato and fruits like apple, grape banana etc cultivated around Visakhapatnam City. The contributions of the vegetables to the daily intake of trace metals from vegetables were investigated. Atomic absorption spectrometry was used to determine the concentrations of these metals in the vegetables and fruits. The average concentrations of each heavy metal regardless of the kind of vegetable and fruits were in the range of 0.003-0.67 and in fruits 0.01-0.95 respectively. It was observed that the concentrations of zinc and cadmium in food crops increased with the degree of contamination of the soil. The vegetables grown in this region are a health hazard for human consumption.

KEYWORDS: Trace metals, atomic absorption spectrophotometer, vegetables, fruits

INTRODUCTION:

Fresh fruits and vegetables are important to the health and well being. Increasing industrialization has been accompanied throughout the world by the extraction and distribution of mineral substances from their natural deposits. Following concentration, many of these have undergone chemical changes through technical processes and finally pass, finely dispersed and in solutions, by way of effluent, sewage, dumps and dust, into the water, the earth and the air and thus into the food chain. These include metals and thus also the heavy metals.

The heavy metals have only become a focus of public interest since analytical techniques have made it possible to detect them even in very small traces. The relatively reckless handling of heavy metals and their compounds in former times can partly be explained by the fact that their effects were unknown. Heavy metal sources, their accumulation in the soil and the effect of their presence in water and soil on plant systems seem to be particularly important issues of present-day research on risk assessments¹. Heavy metals ranks high amongst the chief contaminants of leafy vegetables².

Vegetables take up metals by absorbing them from contaminated soils, as well as from deposits on different parts of the vegetables exposed to the air from polluted environments³. Vegetable plants growing on heavy metal contaminated medium can accumulate high concentrations of trace elements to cause serious health risk to consumers⁴. Excessive content of Pb and Cd in food is associated with etiology of a number of diseases especially with cardiovascular, kidney, nervous as well as bone diseases⁵. Since the dietary intake of food may constitute a major source of long-term low-level body cumulation of heavy metals, the detrimental impact becomes apparent only after several years of exposure. Regular monitoring of these heavy metals from effluents, sewage, in vegetables and in other food materials is essential for preventing excessive buildup of the metals in the food chain. Heavy metal depositions are associated with a wide range of sources such as small scale industries (including battery production, metal products, metal smelting and Cable coating industries); brick kilns; vehicular emissions; re-suspended road dust and diesel generator sets.

Today, analytical detection is possible down to a thousandth of a mg/kg for certain matrixes. The most widely used analytical methods for determination of heavy metals in food are graphite furnace atomic absorption spectrometry (GFAAS) and Inductively Coupled Plasma (ICP).

The concentration of essential elements in foodstuffs of one region may vary from the other since food supplies are affected by various agricultural practices, type of soil, type of fertilizer and chemicals used, type of pesticides and herbicides sprayed. Besides these factors, intake of inorganic elements by the populace of any region may also depend on the geographical location of the area, climatic conditions, eating habits and socio-economic status^6. Leafy vegetables accumulate higher metal contents than others⁷. Most of our water resources are gradually becoming polluted due to the addition of foreign materials from the surroundings. These include organic matter of plant and animal origin, land surface washing, and industrial and sewage effluents⁸.

Metals are essential for important biochemical and physiological functions and are necessary for maintaining health throughout life. In order to assess the impact of human activity on the food chain, monitoring of trace metals in a variety of fruits and vegetables being sold in Visakhapatnam city, Andhrapradesh, India has been focus of this study.

EXPERIMENTAL:

Chemicals and Reagents: All chemicals and reagents taken were of Analytical grade.

Sampling area:

Several samples of Water, Fruits and Vegetables were collected from Agricultural fields in Sabbavaram, Visakhapatnam district. The geographical location is Vishakhapatnam, Andhra Pradesh, India, Asia. The geographical coordinates (Fig.-1) are17° 47' 0" North, 83° 8' 0" East. After collection, the samples were brought to the laboratory and processed further for analysis.

Table I: Determination of trace metals using Atomic absorption spectrophotometer (mg/Kg)

Vegetable/fruit	Nickel	Palladium	Cadmium	Zinc	Copper	Iron
Cabbage	0.17	0.003	2.83	0.15	0.014	0.14
Carrot	0.06	0.02	1.02	0.43	0.058	0.47
Onion	NF	NF	0.4	0.69	0.126	0.45
Tomato	0.47	0.012	NF	0.21	0.087	0.62
Banana	0.42	0.95	NF	0.18	0.096	0.38
Grapes	0.01	0.017	0.3	0.11	0.187	0.68
apple	0.05	NF	0.2	0.07	0.046	0.22

NF=Not found

Sample Preparation:

Vegetables, fruit, crop and plant samples were thoroughly washed to remove all adhered soil particles. Samples were cut into small pieces, air-dried for 2 days and finally dried at 100 ± 1°C in a hot-air oven for 3 h. The samples were ground in warm condition and passed through 1 mm sieve. Digestion of these samples (2 g each) was carried out using 10 ml nitric acid, according to the procedure used for soil samples²⁷. Well-mixed milk samples of 250 ml each were taken in 500 ml glass beakers and digested in 24 ml of aqua regia on a sand bath for 3 days. After evaporation to a lesser volume, the samples were filtered and diluted to 50 ml with distilled water.

Analysis:

Heavy metal analyses were carried out using flame atomic absorption spectrophotometer (Hewlett-Packard) calibration curves were prepared separately for all the metals by running different concentrations of standard solutions. The instrument was set to zero by running the respective reagent blanks. Average values of three replicates were taken for each determination.

RESULTS AND DISCUSSION:

The problem of environmental pollution due to toxic metals has begun to cause concern now in most major metropolitan cities. The toxic heavy metals entering the ecosystem may lead to geoaccumulation, bioaccumulation and biomagnification. Heavy metals like Fe, Cu, Zn, Ni and other trace elements are important for proper functioning of biological systems. Trace Metals like Nickel, Palladium, Cadmium, zinc, copper and iron in various vegetables and fruits were analysed and the results are presented in the table 1

Most of the laboratory research on biosorption of heavy metals indicates that no single mechanism is responsible for metal uptake. In general, two mechanisms are known to occur, viz. ‘adsorption’, which refers to binding of materials onto the surface and ‘absorption’, which implies penetration of metals into the inner matrix⁹.From the results it is found that certain metals are not found. Zinc, Copper and Iron are present in all vegetables and fruits. In general the concentrations of Zn and Cd in food crops increased with the degree of contamination of the soil.

Studies have shown that uptake and accumulation of metals by different plant species depend on several factors, and various researchers have identified several reasons^10-11. The study reveals that sewage is the main source of pollution of this water body and irrigation with sewage-contaminated water containing variable amounts of heavy metals leads to increase in concentration of metals in the soil and vegetation. Concentration of metals in vegetation will provide baseline data and there is a need for intensive sampling of the same for quantification of the results.

CONCLUSION:

The results obtained in this work on concentration of heavy metals of some selected common fruits and leafy vegetables compared well with similar samples from other published works. Generally, the levels of heavy metals were observed to be lower than those of previous published works.

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Received on 03.10.2011 Modified on 20.10.2011

Asian J. Research Chem. 4(11): Nov., 2011; Page 1769-1771