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Elemental Status of Bangladeshi Tea Using Instrumental Neutron Activation Analysis Method

M. Oyes Kurni
Department of Physics, Shahjalal University of Science and Technology, Sylhet, Bangladesh

Tanwir O. Ahsan
Department of Mathematics, Shahjalal University of Science and Technology, Sylhet, Bangladesh

Faisal Kabir
Department of Physics, Shahjalal University of Science and Technology, Sylhet, Bangladesh

Syed Mohammod Hossain
Institute of Nuclear Science and Technology, AERE, Savar, Dhaka, Bangladesh.

M.H. Ahsan
Department of Physics, Shahjalal University of Science and Technology, Sylhet, Bangladesh

Abstract/ Executive Summary:

Elemental status of Bangladeshi tea was checked using nuclear reactor based Instrumental Neutron Activation Analysis (INAA) method. The analytical results of thirteen samples have been reported here. Irradiation of samples and standards were performed at the dry central thimble (DCT) facility of the 3.0 MW TRIGA Mark-II research reactor of AERE, Savar, Dhaka. The irradiated samples and standards were measured twice with different decay intervals depending on the half lives of the interested elements using High Purity Germanium (HPGe) detectors coupled with PC based digital gamma spectrometry system. The gamma peak analysis was performed using the software Hypermet PC version 5.12. The concentration calculations were performed based on relative standardization approach. The quality control of the analysis was performed by analyzing Certified Reference Material NIST 1515 (Apple leaves), NIST 1547 (Peach leaves), NBS 1572 (Citrus leaves) and NIST 1573a (Tomato leaves) relative to NIST 1633b (Coal fly ash) and comparing the measured values with certified ones. The uncertainties were calculated based on the total uncertainty budget of the NAA method. Almost all the source of uncertainty was considered for this calculation. Based on the long irradiation, the elements samarium (Sm), Lanthanum (La), Bromine (Br), Sodium (Na), Potassium (K), Cerium (Ce), Chromium (Cr), Cesium (Cs), Scandium (Sc), Rubidium (Rb), Cobalt (Co) and Iron (Fe) were determined quantitatively and qualitatively. The results showed that that Bangladeshi tea contained high concentration of Na and K; and low concentration of Sm and Sc. The concentrations of Na and K are in the range of 146.4 – 5969.6 μg/g and 11764.2 – 20557.0 μg/g, respectively. The measured concentration of all these elements compared with the world reference values. Most of the elements are in the normal level whereas some elements like Na and Cr exceeded our reference values, but do not exceed the accepted permissible level. The analytical result gives a baseline data of elemental content of Bangladeshi tea and will help to assess further information in future.

Keywords: Instrumental Neutron Activation Analysis, Gamma spectrometry, Certified reference material, Permissible level.

Location: Institute of Nuclear Science and Technology (INST), Atomic Energy Research Establishment (AERE), Savar, Dhaka.

Start Date:

End Date:

Program Area: Quality and Nutrition

Commodity: Tea

Objectives:

To determine elemental status of Bangladeshi Tea using instrumental neutron activation analysis method.

Methodology:

A total of thirteen (about 100 g each) different brands of Bangladeshi tea samples were collected from local markets of Sylhet and Dhaka to check their elemental status using Neutron Activation Analysis (NAA) technique at the Institute of Nuclear Science and Technology (INST), Atomic Energy Research Establishment (AERE), Savar, Dhaka. The collected tea samples were namely Pran Tea, Pusti, Ispahani Mirzapur Tea, Banoful Garden Tea, Tetley, Mam, Nishita Clone Tea, Prio Black Tea, Al-Amin Black Tea, National Tea, Priya Tea, Karnaphuli, HRC Clevedon Tea. After collection, all the samples were dried at about 100°C in an oven until having constant weight to remove the moisture and crushed into fine powder with an agate mortar and pestle. These samples were then transferred into ultra clean polyethylene vial. The fine powder like tea samples were then weighed each of about 80 mg into plastic bags (special types of plastic bags used for long irradiation). The plastic bags were then sealed and preserved carefully for irradiation. To apply relative standardization approach, we used five standards: NIST-1633b (Coal Fly Ash), NIST-1515 (Apple Leaves), NIST-1547 (Peach Leaves), NBS-1572 (Citrus Leaves) and NIST-1573a (Tomato Leaves). Each of the standards was prepared in the same way as the sample.

Source of Information: SUST Journal of Science and Technology, Vol. 20, No. 6, 2012; P:15-35

Article Link (Online Journal): http://sustjournals.org/uploads/archive/81c276f4c37a614e921aa3b762d79dfb.pdf

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The summary of our findings are presented here briefly.

Twelve elements from Bangladeshi tea samples have been detected. They are Sm, La, Br, Na, K, Ce, Cr, Cs, Sc, Rb, Co and Fe.
Baseline concentration data of these elements are established for future use.
Concentration of some elements (Sm, Na and Cr) are at a high level compared to world references. Among these three elements Sm concentrations is not far away compared to other countries.

The average concentration of Cr in Bangladeshi tea is 43.14 μg/g whereas the recommended dietary allowances of Cr for adults are 50 μg to 200 μg [1]. As a component of a natural substance called glucose tolerance factor, chromium works with insulin to regulate the body's use of sugar and is essential to fatty-acid metabolism. Its contribution to metabolism makes chromium a helpful supplement in weight loss programs. Additional evidence suggests that chromium may help deter atherosclerosis and reduce risk of cardiovascular disease. Inadequate chromium can result in alcohol intolerance, elevate blood sugar levels, and possibly induce diabetes-like symptoms such as tingling in the extremities and reduced muscle coordination. Chromium is not absorbed well, so the body must take in far more than it uses. Most people do not get enough dietary chromium and some may benefit from a multinutrient supplement. Supplemental chromium may be used to treat some cases of adult-onset diabetes, to reduce insulin requirements of some diabetic children, and to relieve symptoms of hypoglycemia. Taken regularly in supplements greater than 1000 μg, however, chromium inhibits insulin's activity and can be toxic. The average concentration of Na in Bangladeshi tea is 1065.23 μg/g whereas the recommended dietary allowance of Na for adults is 500 mg [2]. Most of the sodium in our daily diets is from table salt. Among many other sources are processed foods, soft drinks, meats, shellfish, condiments, snack foods, food additives, and over-the-counter laxatives. Individuals generally consume far too much sodium. A single teaspoon of salt contains 2000 mg - four times the daily minimum - but average daily consumption in the U.S. ranges from 3000 mg to 7000 mg [2]. Keeping sodium intake within reasonable limits is critical for long term health. When sodium levels are persistently elevated, the body loses potassium and retains water, making blood pressure rise. Adopting a low-sodium diet can reduce high blood pressure (hypertension) and correct a potassium deficiency. Overexertion can induce temporary sodium deficiency, characterized by nausea, dehydration, muscle cramps, and other symptoms of heatstroke. Therefore, we can say that our Na and Cr concentration is also alright. We could not get to study some elements, such as Pb, Zn, Mn, Sb, In, Ca, Mg, because our SRMs do not contain such elements. These elements are studied extensively throughout the world and we also need to study them without any delay to know their present status for our country. Here is our end, but may be, this is the starting point for others. We hope that our works have paved the way for other researchers to study much more about elemental composition of Bangladeshi tea.

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