Analytical methods for heavy metals in herbal medicines.

Introduction: It is estimated that about 70-80% of the world's population relies on non-conventional medicine, mainly of herbal origin. However, owing to the nature and sources of herbal medicines, they are sometimes contaminated with toxic heavy metals such as lead, arsenic, mercury and cadmium, which impose serious health risks to consumers. It is critical to analyse source materials for heavy metals in order to ensure that their concentrations meet the related standards or regulations limiting their concentrations in herbal medicines. In this review, different analytical methods for analysis of heavy metals in herbal medicines are discussed.

Objective: To provide a comprehensive review of the current state of the art in analytical methods used to detect heavy metals in herbal medicines.

Methodology: We systematically searched and reviewed the research articles regarding analytical methods for heavy metals in herbal medicine from various databases, such as Medline/PubMed, ScienceDirect, SciFinder, Google Scholar, EBSCO, Gale InfoTrac, Ingenta, Ovid, ProQuest and ISI Web of Knowledge.

Results: In this review, we discuss in detail several commonly used and sensitive analytical techniques, including atomic absorption spectrometry, inductively coupled plasma optical emission spectrometry or mass spectrometry, X-ray fluorescence spectrometry, high-performance liquid chromatography, differential pulse polarography, neutron activation analysis and anodic stripping voltammetry. We also provide some application examples of these analytical techniques for heavy metals in herbal medicines.