Investigation of Metals in Ethiopian Tobacco Leaves and Processed Tobacco
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Date
2007-03
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Addis Ababa Universty
Abstract
Samples of tobacco leaves (Virginia type) were collected from two different regions of
Ethiopia (Bilatte and Shoa Robit) which are the only places where this type of tobacco is
harvested. The other three processed tobacco samples were collected from tobacco
manufacturing factory in Addis Ababa, Ethiopia. After collection of the representative
amounts of samples, and samples pretreatment, different digestion procedures were tested
by varying reagent volumes, time of digestion, temperature of digestion, and amount of
the sample to develop a procedure that consume less reagent volume, short digestion
time, low temperature of digestion and smaller mass of the sample. The optimal
procedure required 3:30 hours and consumes 3 mL HNO3 (69-72 %) and 3 mL HClO4
(70 %) to completely digest 0.5 g of both tobacco leaves and processed tobacco samples.
The accuracy of the optimized procedure was evaluated by analyzing the digest of the
spiked samples with standard solution. Recoveries of the spiked samples varied from
88.3% to 104.3% and 91.7% to 107% for leaves and processed tobacco, respectively.
Concentrations of metals in the samples; (Cd, Cr, Cu, Ni, Pb and Zn) were analyzed by
flame atomic absorption spectrometer employing a four point external calibration curve.
The observed average metals concentrations were (mean ± ts/N1/2, μg/g at 95% CL and
N=9): Cu (4.38 ± 0.11), Zn (53.7 ± 0.96), Cd (1.2 ± 0.05) in tobacco leaves collected
from Bilatte; Cu (7.3± 0.19), Ni (1.9 ± 0.08), Cd (1.3 ± 0.04), Cr (1.45 ± 0.11), Zn (33.15
±1.9) in leaves collected from Shoa Robit; Cu (9.8 ± 0.04), Ni (2.35 ± 0.19) Cd (1.45 ±
0.023), Cr (1.65 ± 0.08), Zn (101.2 ± 0.4) in processed tobacco leaves originated from
Bilatte; Cu (12.8 ± 0.11) Ni (2.2 ± 0.05) Cd (1.9 ± 0.05), Cr (1.75 ± 0 .08), Zn (83.75 ± 0
.4) in processed tobacco leaves originated from Shoa Robit; Cu (8.95 ± 0.31), Cd (1.55 ±
0.02), Cr (1.62 ± 0.11), Ni (4.7 ± 0.04), Zn (79.3 ± 0.77) in Nyala. The Concentration of Pb was lower than detection limit of the instrument (0.1 mg/L) in all tobacco samples; Cr
and Ni in tobacco leaves from Bilatte (0.05 and 0.04 mg/L respectively). This study
showed that the metal contents of tobacco leaves varied with the geographical origin in
which the tobacco plant grows, and the metal contents of processed tobacco were higher
than the corresponding leaves. The levels of metals in Ethiopian tobacco are comparable
with that of other countries.
Key words: Tobacco leaves, Processed tobacco, Trace metals, FAAS
Description
Keywords
Tobacco leaves; Processed tobacco; Trace metals; FAAS