Determination of essential and non-essential elements of commercialized rooibos tea samples using microwave-assisted digestion prior to analysis using inductively coupled plasma-optical emission spectroscopy: Human health risk assessments

The primary aim of this study was to evaluate human health risks associated with elemental exposure from rooibos tea infusions by analyzing the concentrations of essential and non-essential elements in commercially available samples purchased in Florida Park, Roodepoort, South Africa. The study developed and optimized a microwave-assisted digestion method (P2), which comprised of 9 mL of 5 M H₂O₂ and 1 mL of 70 % (v/v) HNO₃ were used for the preparation of rooibos samples. Compared to other methods, P2 demonstrated excellent precision, making it the preferred approach for preparing tea infusion samples. Inductively coupled plasma-optical emission spectroscopy revealed the mean concentration levels of Al, Ba, Cd, Cr, Cu, Fe, Mn, Mo, Pb, Sb, Sn, V, and Zn across all the tea samples in the range of 73.50 – 198.8, 1.982 – 16.6, 0.118 – 4.632, 0.168 – 4.640, 1.213 – 13.78, 86.25 – 194.0, 27.18–56.14 , 3.342 – 5.322, 0.978 – 2.978, 16.581 – 21.872, 11.34 – 19.87, 1.267 – 3.295, and 28.96 – 321.7 µg/g, respectively . While these findings suggest a low risk, the study underscores the necessity of continuous monitoring and assessment of metal contaminants in tea products to safeguard consumer health.