Herbal remedies, especially Traditional Chinese Medicines (TCMs), are becoming more popular worldwide. Because they are not regulated and can be purchased “over the counter,” it is important to evaluate their safety. With recent technological advances, people are becoming more aware of the risks associated with the presence of heavy metals, such as mercury (Hg), arsenic (As), lead (Pb), and cadmium (Cd), in some of these products.
Herbal remedies are very complex and contain many elements over a wide concentration range. In the past, they have been analyzed by a combination of spectroscopic methods, including atomic fluorescence spectroscopy (AFS) and atomic emission spectroscopy (AES). These procedures are time-consuming and costly. ICP-MS is fast becoming the technique of choice for the determination of elements in a wide range of samples because it delivers an unequaled combination of advantages:
- Widest dynamic range (nine orders of magnitude, from 1 pg/mL to 1000 µg/mL)
- Lowest detection limits for trace elements such as toxic heavy metal impurities
- Ability to rapidly and accurately measure multiple elements simultaneously
In a recent study, scientists at the Capital Normal University in Beijing analyzed thirteen toxic elements in seven TCM preparations that were purchased on the market. They used microwave digestion for sample preparation and an Agilent 7500c ICP-MS to determine element concentrations.
The study showed that while the levels of toxic elements were low in most of the natural products, some TCM preparations contained toxic elements that were well above legal limits. For example, the Shugan Pill exceeded both the limit for Hg (0.2 ppm) and As (2.0 ppm), as defined in the 2005 Pharmacopoeia of the People’s Republic of China.
With optimized working parameters, the scientists in Beijing simultaneously analyzed all thirteen elements in the seven medicines with an Agilent 7500c ICP-MS.
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Determination of Trace and Major Elements in Traditional Chinese Medicine (TCM) |