title: Determination of heavy metals in the soils of tea plantations and in fresh and processed tea leaves: an evaluation of six digestion methods.
abstract: BACKGROUND
  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.
  
  
  METHODS
  Graphite 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.
  
  
  RESULTS
  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). 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.
  
  
  CONCLUSIONS
  Overall, the present study gives current insights into the heavy metal levels both in soils and teas commonly consumed in Bangladesh.
authors.affiliation: Agrochemical and Environmental Research Division, Institute of Food and Radiation Biology, Bangladesh Atomic Energy Research Establishment, Savar, Dhaka, 1349 Bangladesh.
authors.forename: Md Harunur
authors.initials: MH
authors.lastname: Rashid
authors.affiliation: Food Analysis and Research Laboratory, Center for Advanced Research in Sciences, University of Dhaka, Dhaka, Bangladesh.
authors.forename: Zeenath
authors.initials: Z
authors.lastname: Fardous
authors.affiliation: Agrochemical and Environmental Research Division, Institute of Food and Radiation Biology, Bangladesh Atomic Energy Research Establishment, Savar, Dhaka, 1349 Bangladesh.
authors.forename: M Alamgir Zaman
authors.initials: MA
authors.lastname: Chowdhury
authors.affiliation: Agrochemical and Environmental Research Division, Institute of Food and Radiation Biology, Bangladesh Atomic Energy Research Establishment, Savar, Dhaka, 1349 Bangladesh.
authors.forename: Md Khorshed
authors.initials: MK
authors.lastname: Alam
authors.affiliation: Food Analysis and Research Laboratory, Center for Advanced Research in Sciences, University of Dhaka, Dhaka, Bangladesh.
authors.forename: Md Latiful
authors.initials: ML
authors.lastname: Bari
authors.affiliation: Department of Pharmacology, School of Medical Sciences, Universiti Sains Malaysia, Kubang Kerian, 16150 Kota Bharu, Kelantan Malaysia.
authors.forename: Mohammed
authors.identifier: 0000-0003-3498-7758
authors.initials: M
authors.lastname: Moniruzzaman
authors.affiliation: Human Genome Centre, School of Medical Sciences, Universiti Sains Malaysia, Kubang Kerian, 16150 Kota Bharu, Kelantan Malaysia.
authors.forename: Siew Hua
authors.initials: SH
authors.lastname: Gan
keywords: Black tea; Dry ashing; Fresh tea; GF-AAS; Heavy metals; Hydrogen peroxide; Nitric acid; Perchloric acid