Determination of heavy metal concentrations in tea samples taken from Belgrade market, Serbia

Abstract

Tea is one of the world's most popular beverages. Economic and social interest in tea is clear from the fact that about 18-20 billion tea cups are being consumed daily in the world. Consequently, chemical components in tea leaves have received great interest because they are related to health and disease. Various reports have discussed the potential health implications of some chemical factors such as heavy metals in tea, particularly since tea bush is known to accumulate trace metals. Metallic constituents of tea leaves depend on the type of tea and geological origin. In the present study four tea samples (two black and two green) and four herbal tea samples (two Mentha piperita and two Matricaria chammomilla) were collected from the local market in Belgrade, Serbia, in May 2008. The sample preparation has been performed using wet and dry digestion procedures. The metal content (Cu, Zn, Mn, Cd, Ni and Pb) in the digested samples has been analyzed by using flame atomic absorption spectrometry. The comparison of wet and dry digestion has shown significant differences in results, indicating that dry digestion is more appropriate method. The levels of the examined metals obtained by dry digestion in this study compared well with those reported for tea samples from some other parts of the world. Among the investigated metals, the most abundant nutritive metal, Mn, has been the highest with 26.0 to 199.3 mg/kg, while fortunately toxic heavy metal, Cd, has been below the detection limit (0.1 mg/kg). The concentrations of lead and nickel have been in the range 5.1-13.7 and 1.4- -4.4, respectively. The content of lead in two samples (Mentha piperita) has been higher than the maximum permissible concentration of 10 mg/kg specified by the national legislation.

U ovom radu su ispitivane koncentracije bakra, cinka, mangana, nikla, kadmijuma i olova u uzorcima čajeva (crni, zeleni, nana, kamilica) uzetih iz lokalnih prodavnica u Beogradu u maju 2008. godine. Priprema uzoraka vršena je mokrom i suvom digestijom. Koncentracije odabranih metala u rastvorima posle digestije određivane su plamenom atomskom apsorpionom spektrofotometrijom. U svim uzorcima posle suve digestije, najviša je bila koncentracija mangana (26,0 do 199,3 mg/kg), dok kadmijum nije detektovan ni u jednom uzorku. Sadržaj bakra je varirao od 7,7 do 14,1 mg/kg, cinka od 6,9 do 26,9 mg/kg, olova od 5,1 do 13,7 mg/kg, a nikla od 1,4 do 4,4 mg/kg. U oba ispitivana uzorka čaja od lista nane koncentracija olova je bila iznad 10 mg/kg, koliko je dozvoljeno zakonskom regulativom Republike Srbije.