A Comprehensive Review of Contamination, Analytical Techniques, Quality Control and Safety

Herbal drug formulations are increasingly used as traditional, complementary and supportive healthcare products. Although their botanical origin is often associated with natural safety, medicinal plants can accumulate potentially toxic elements from soil, irrigation water, atmospheric deposition, agricultural inputs and contaminated processing environments. Lead, cadmium, mercury and arsenic are among the most important contaminants because repeated exposure can produce neurological, renal, cardiovascular, hematological and other systemic effects. Consequently, determination of elemental contaminants is an essential part of the quality assessment of herbal medicines. This review presents an integrated discussion of the occurrence and significance of toxic elements in herbal drug formulations, environmental and manufacturing sources of contamination, plant uptake and translocation, sampling, homogenization and digestion, conventional limit tests, atomic absorption spectrometry, inductively coupled plasma optical emission spectrometry, inductively coupled plasma mass spectrometry, X-ray fluorescence and electrochemical approaches. It further discusses method validation, quality-control samples, calibration, blanks, recovery, detection limits, uncertainty and regulatory interpretation. A reliable analytical strategy begins with representative sampling and suitable sample preparation and ends with a scientifically justified interpretation of the measured concentration. Modern multi-element techniques provide sensitive and efficient analysis, but their performance depends on matrix control, contamination prevention and appropriate validation. Risk-based control across cultivation, procurement, processing and finished-product testing provides stronger consumer protection than reliance on a single end-product test.