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. 2016 Jan;24(1):46-55.
doi: 10.1016/j.jfda.2015.04.010. Epub 2015 Jul 18.

Determination of Pb (Lead), Cd (Cadmium), Cr (Chromium), Cu (Copper), and Ni (Nickel) in Chinese tea with high-resolution continuum source graphite furnace atomic absorption spectrometry

Wen-Si Zhong  1 , Ting Ren  2 , Li-Jiao Zhao  2
Affiliations

Determination of Pb (Lead), Cd (Cadmium), Cr (Chromium), Cu (Copper), and Ni (Nickel) in Chinese tea with high-resolution continuum source graphite furnace atomic absorption spectrometry

Wen-Si Zhong et al. J Food Drug Anal. 2016 Jan.

Abstract

The contents of lead, cadmium, chromium, copper, and nickel were determined in 25 tea samples from China, including green, yellow, white, oolong, black, Pu'er, and jasmine tea products, using high-resolution continuum source graphite furnace atomic absorption spectrometry. The methods used for sample preparation, digestion, and quantificational analysis were established, generating satisfactory analytical precisions (represented by relative standard deviations ranging from 0.6% to 2.5%) and recoveries (98.91-101.32%). The lead contents in tea leaves were 0.48-10.57 mg/kg, and 80% of these values were below the maximum values stated by the guidelines in China. The contents of cadmium and chromium ranged from 0.01 mg/kg to 0.39 mg/kg and from 0.27 mg/kg to 2.45 mg/kg, respectively, remaining in compliance with the limits stipulated by China's Ministry of Agriculture. The copper contents were 7.73-63.71 mg/kg; only 64% of these values complied with the standards stipulated by the Ministry of Agriculture. The nickel contents ranged from 2.70 mg/kg to 13.41 mg/kg. Consequently, more attention must be paid to the risks of heavy metal contamination in tea. The quantitative method established in this work lays a foundation for preventing heavy metal toxicity in human from drinking tea and will help establish regulations to control the contents of heavy metals in tea.

Keywords: Chinese tea; continuum source graphite furnace atomic absorption spectrometry; heavy metals; quantitative analysis.

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Conflict of interest statement

Conflicts of interest

The authors declare that there are no conflicts of interest.

Figures

Fig. 1
Fig. 1
Pyrolysis and atomization temperature curves for lead, cadmium, chromium, copper, and nickel. 1, no matrix modifier; 2, 3, and 4: with 2 μL, 5 μL, and 10 μL of modifier, respectively. (10 g/L NH4H2PO4 solution for Pb and Cd; 1 g/L Mg(NO3)2 solution for Cr; 0.5 g/L Mg(NO3)2 solution for Cu and Ni). Cd = cadmium; Cr = chromium; Cu = copper; Ni = nickel; Pb = lead.
Fig. 2
Fig. 2
The nonlinear standard curves for lead, cadmium, chromium, copper, and nickel. Cd = cadmium; Cr = chromium; Cu = copper; Ni = nickel; Pb = lead.
Fig. 3
Fig. 3
Lead, cadmium, chromium, copper, and nickel contents in tea samples determined with high-resolution continuum source-graphite furnace atomic absorption spectrometry. Cd = cadmium; Cr = chromium; Cu = copper; Ni = nickel; Pb = lead.
Fig. 4
Fig. 4
Distribution of the lead, cadmium, chromium, copper, and nickel contents in the seven types of tea. Cd = cadmium; Cr = chromium; Cu = copper; Ni = nickel; Pb = lead.
See this image and copyright information in PMC

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