Determination of heavy metals and anthraquinone in black tea

A rapid and simple method was investigated for determining the concentration of some contaminants including heavy metals such as lead (Pb), cadmium(Cd), chromium (Cr), and anthraquinone in black tea samples in Iran.

Heavy metals such as Pb, Cd, and Cr in tea samples were detected using inductively coupled plasma optical emission spectrometry (ICP-OES) after microwave acid digestion (MAD). The anthraquinone in infusion tea samples was determined via liquid chromatography photodiode array detector after the dispersive liquid-liquid microextraction method (DLLME). 

Recoveries of all the tea samples in heavy metals and anthraquinone were in the range of 75% - 89% and 71%-96, respectively. The results of recoveries are in the range of the Association of Official Analytical Chemists (AOAC) and the European Union. RSD in the MAD and DLLME methods was less than 5%. The mean concentrations of Pb, Cd, Cr, and anthraquinone were 0.724, 0.021, 2.98 ppm, and 2.27 ppb.

Overall our results showed that MAD and DLLME methods could successfully determine the concentration of some contaminants such as Pb, Cd, Cr, and anthraquinone in black tea samples.