ICP-MS for Determination of Heavy Metals in Dietary Supplements

Dietary supplements are being used by an ever increasing number of people, but their safety is left up to manufacturers, who often rely on independent analysis to ensure that contaminants are not present. Heavy metals, associated with several serious health conditions, comprise a major class of contaminant that could lead to public health concerns if allowed to be distributed. ICP-MS is a multi-elemental detection technique that is well-suited to dietary supplement analysis for the determination of heavy metals, providing fast detection with excellent sensitivity and adaptability to sample types. These factors increase the cost-effectiveness of the method, enabling more quality control to be achieved, and thus increasing consumer safety.

Significance

Heavy metals, including arsenic, cadmium, mercury and lead are found naturally in the Earth's crust and are used and produced as byproducts in a wide range of industries. Some of these metals are essential to metabolic processes at low levels but all can be quite toxic to humans and other animals. One common method of toxicity is through contaminated food and nutritional products. Modern lifestyles have produced an increasing number of people who are too busy to prepare and eat nutritionally balanced meals, but who are also health conscious and at least moderately affluent. For many, nutritional supplements provide an easy means to remedy such deficiencies. For many others, natural remedies such as herbs or Traditional Chinese Medicines (TCM) offer a means to avoid or mitigate increasing costs of health care.

For these reasons, the manufacture and use of dietary supplements has risen at rapid rates over the past few decades, especially in the industrialized nations of North America and Europe. Vitamins and other dietary supplements sold in the United States are regulated under the Dietary Supplement Health and Education Act of 1994 by the Food and Drug Administration. These supplements include tablets, powders and liquids that are taken orally, and may contain vitamins, minerals, herbs, amino acids, and metabolites. Under FDA regulations, manufacturers and distributors are responsible for ensuring that their products do not contain any harmful substances, including heavy metals.

The presence of these materials can be due to the raw material growing conditions, extraction procedures, or contamination during the manufacturing process. Elevated levels of lead and mercury have previously been discovered in nutritional supplements, and all four common toxic metals are often found in analyses of TCM formulations shipped to the U.S. from East Asia (1). Further complicating matters, several of these metals can be present as multiple species, some of which are more toxic than others. For example, organic methyl mercury is more toxic than other mercury species, while inorganic arsenic oxides are much more poisonous than their organic counterparts (4). For these reasons, the development of precise and efficient analytical methods for determining the elemental compositions of dietary supplements is crucial for public safety.

ICP-MS can provide precise determination of heavy metal contamination in dietary supplements, allowing for simultaneous analysis for a wide range of elements and their isotopes. This single-run determination provides several critical advantages, such as the time and money savings for analysis, as well as the increased public safety that results from rapid screening procedures. Trained technicians can analyze more than 50 separate samples in an hour with this method, greatly enhancing productivity (2). The high linear dynamic range (LDR) provided by lCP-MS enables the determination of both low and high concentrations of species, allowing the detection of minute quantities of ultra-trace minerals as well as major elements in the same run. The high signal-to-noise ratio provided by the technique as well as the ease of calibration, ensure that results from ICP-MS analysis can be trusted. These benefits bring down the costs of laboratory analysis, providing greater incentive for manufacturers to have their products tested, and make independent analysis more affordable and commonplace. Furthermore lCP-MS can be readily combined with HPLC or other separation techniques for speciation analysis.

Part 2: Instrumentation up next.