Ayurveda, one of the oldest systems of medicine, was thrown into the controversy in early, 2005 after Dr. Robert B. Saper of Department of Family Medicine, Boston Medical School published an article in JAMA in December 2004. Based on the analysis of samples of herbal medicinal products collected from grocery stores, they had concluded that one out of every five Ayurvedic herbal medicinal product originating from South Asia was contaminated with toxic levels of heavy metals and potentially unsafe for consumption.

In response to this, the Department AYUSH imposed mandatory testing of heavy metals for all Ayurveda, Siddha, and Unani herbal products being exported from India, though these tests were already part of Good Manufacturing Practices notified in 2003.

With the emergence of the new testing requirement manufacturer and buyers alike were faced with the difficult decision of choosing a suitable analytical technique and testing lab to meet the requirement. Products being exported were invariably being retested in Europe and America for the presence of heavy metals and reproducibility of results became a primary requirement. The choices offered by testing labs varied from more conventional chemical analysis to the use of, Atomic Absorption Spectrometer (AAS) and the most advanced, Inductively Coupled Plasma Mass Spectrometer (ICPMS). The decision was further complicated when it came to light that the digestion technique used for preparing the samples also had a great impact on the results. Some testing labs were using conventional open digestion with acids, while some are ashing the samples in a furnace prior to acid treatment and a few were using closed digestion techniques like microwave digestion or high-pressure ashing. The use of various combinations and permutations of the sample preparation technique and analytical technique lead to greater variability in results, with little or no reproducibility between labs.

From this confusion, one technique arose as the gold standard as it gave the highest recovery for all metals and thus if a sample was passing using this combination of techniques, it will pass in all other techniques as well. This combination was that of using a microwave digestion system for sample preparation and conducting the sample analysis using inductively coupled plasma mass spectrometer.

Microwave Digestion system

The closed sample digestion technique of microwave digestion system allowed for preparing the samples in a closed system at high temperature and pressure without losing any of the volatile analytes like mercury and arsenic, which are otherwise easily lost when sampling the digested using open digestion with acids or ashing followed by acid treatment.

Inductively Coupled Plasma Mass Spectrometer

ICP MS gave the advantage of analyzing all the metals at the same time with minimum manual intervention, which is required when analyzing samples on an AAS with hydride generation and graphite furnace assembly. It also offered unparalleled low detection limits, in the parts per trillion levels, allowing for the use of smaller sample quantities which can be properly digested giving better recovery and reproducibility of results.