Abstract
BackgroundThe aim of this study was to determine the levels of cadmium (Cd), chromium (Cr), lead (Pb), arsenic (As) and selenium (Se) in (1) fresh tea leaves, (2) processed (black) tea leaves and (3) soils from tea plantations originating from Bangladesh.MethodsGraphite furnace atomic absorption spectrometry (GF-AAS) was used to evaluate six digestion methods, (1) nitric acid, (2) nitric acid overnight, (3) nitric acid–hydrogen peroxide, (4) nitric–perchloric acid, (5) sulfuric acid, and (6) dry ashing, to determine the most suitable digestion method for the determination of heavy metals in the samples.ResultsThe concentration ranges of Cd, Pb, As and Se in fresh tea leaves were from 0.03–0.13, 0.19–2.06 and 0.47–1.31 µg/g, respectively while processed tea contained heavy metals at different concentrations: Cd (0.04–0.16 µg/g), Cr (0.45–10.73 µg/g), Pb (0.07–1.03 µg/g), As (0.89–1.90 µg/g) and Se (0.21–10.79 µg/g). Moreover, the soil samples of tea plantations also showed a wide range of concentrations: Cd (0.11–0.45 µg/g), Pb (2.80–66.54 µg/g), As (0.78–4.49 µg/g), and Se content (0.03–0.99 µg/g). Method no. 2 provided sufficient time to digest the tea matrix and was the most efficient method for recovering Cd, Cr, Pb, As and Se. Methods 1 and 3 were also acceptable and can be relatively inexpensive, easy and fast. The heavy metal transfer factors in the investigated soil/tea samples decreased as follows: Cd > As > Se > Pb.ConclusionOverall, the present study gives current insights into the heavy metal levels both in soils and teas commonly consumed in Bangladesh.
Highlights
The aim of this study was to determine the levels of cadmium (Cd), chromium (Cr), lead (Pb), arsenic (As) and selenium (Se) in (1) fresh tea leaves, (2) processed tea leaves and (3) soils from tea plantations originating from Bangladesh
The concentration ranges of Cd, Pb, As and Se in fresh tea leaves were from 0.03–0.13, 0.19–2.06 and 0.47–1.31 μg/g, respectively while processed tea contained heavy metals at different concentrations: Cd (0.04– 0.16 μg/g), Cr (0.45–10.73 μg/g), Pb (0.07–1.03 μg/g), As (0.89–1.90 μg/g) and Se (0.21–10.79 μg/g)
Six digestion methods followed by Graphite furnace atomic absorption spectrometry (GF-AAS) have been successfully optimized in the present study
Summary
The aim of this study was to determine the levels of cadmium (Cd), chromium (Cr), lead (Pb), arsenic (As) and selenium (Se) in (1) fresh tea leaves, (2) processed (black) tea leaves and (3) soils from tea plantations originating from Bangladesh. Tea is consumed in all of Bangladesh throughout the year, and Bangladesh is one of the leading tea producing and exporting countries in the world [8]. Tea processing and packaging in Bangladesh is dependent on the type of tea, with a wide variety available in the country that is produced by different processing steps. The leaves are rolled and oxidized, which alters their flavor and gives the processed tea its final appearance and color. The step involves firing (final drying process), a process that is initiated once the tea leaves have dried. This is followed by visually sorting into various batches of similar sizes and color before being packaged and commercialized both nationally and internationally. The leaves are completely oxidized before they are dried, which is how they acquire their dark color and rich flavor
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