Optimised determination of arsenic and lead in tea samples using microwave-assisted digestion and ICP-MS: method validation and health risk assessment

Heavy metal contamination in tea poses significant risks to consumer health, necessitating the development of accurate and efficient analytical methods for routine monitoring. This study aimed to optimise and validate a robust process for the simultaneous determination of arsenic (As) and lead (Pb) in dried tea samples using inductively coupled plasma mass spectrometry (ICP-MS) following microwave-assisted digestion. These toxic elements were selected due to their known health risks and their frequent detection in tea. The method was systematically optimised for digestion parameters and validated following EURACHEM guidelines to ensure accuracy and precision. Key validation metrics included linearity (R2 >= 0.9999), limits of quantification (LOQ) of 0.25 mu g/kg for As and 1.5 mu g/kg for Pb, sufficient for regulatory compliance. The method demonstrated excellent mean recoveries (75%-89%) and relative standard deviations (RSDs) below 15% across all fortification levels. Precision and accuracy were further verified through proficiency testing, yielding acceptable z-scores for both analytes. Application of the validated method to tea samples collected from Egypt revealed arsenic concentrations ranging from 0.018 +/- 0.004 to 0.280 +/- 0.070 mg/kg and lead concentrations from 0.083 +/- 0.021 to 1.630 +/- 0.407 mg/kg. Although detection rates were elevated, the calculated target hazard quotient (THQ) values for As and Pb were below the threshold of 1, suggesting no significant non-carcinogenic health risks associated with tea consumption. This study provides a reliable, cost-effective analytical framework for monitoring heavy metal contamination in tea products, supporting consumer safety and public health initiatives.