ICP-MS for Detecting Heavy Metals in Foodstuffs

Heavy metals can be toxic for humans when they are not metabolized by the body and accumulate in the soft tissues. Depending on the heavy metal in question, toxicity can occur at levels just above naturally occurring background levels, meaning that consumption of food with a high heavy metal concentration can cause acute or chronic poisoning. Poisoning can result in damaged or reduced mental and central nervous function as well as damage to blood composition, lungs, kidneys, liver, and other vital organs. Long-term exposure to heavy metals may result in slowly progressing physical, muscular, and neurological degenerative conditions as well as cancer.

Arsenic (As), cadmium (Cd), mercury (Hg), lead (Pb), and inorganic tin (Sn) are the most toxic heavy metals that account for most heavy metal poisoning cases. Poisoning is usually a result of environmental pollution or chronic intake of foods high in these metals. Levels of arsenic are usually high in fish and seafood because these organisms absorb and accumulate arsenic from the environment. Cadmium, found in soil because of insecticides, fungicides, sludge, and commercial fertilizers, can contaminate agricultural food products. Some foodstuffs are naturally rich in cadmium, such as liver, mushrooms, shellfish, mussels, cocoa powder, and dried seaweed. Mercury is generated naturally in the environment from volcanic emissions. It is then dispersed across the globe by winds, returning to the earth in rainfall and accumulating in aquatic food chains. Mercury can also contaminate crops sprayed with mercury-containing pesticides.

Typical sample preparation for metals in foodstuffs.

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Figure 1. Typical sample preparation for metals in foodstuffs.

Food Safety Legislation

Driven by consumer demand and quality, many food agencies have introduced directives that stipulate maximum allowable concentrations for heavy metals in foodstuffs. The European Commission directive 1881/2006 specifies maximum levels for Cd, inorganic Sn, Hg, and Pb in a variety of foodstuffs, with, for example, 0.02 mg Pb/kg allowable in milk products and up to 1.5 mg Pb/kg allowable in bivalve mollusks.

The U.S. Food and Drug Administration (FDA) enforces action levels for poisonous or deleterious substances in human food and animal feed, including cadmium, lead, mercury, and others.1 The FDA has also developed a comprehensive Food Protection Plan to address the challenges and changes occurring in food sources, production, and consumption.2 The plan builds upon advances in science and technology to protect the nation’s food supply from both unintentional contamination and deliberate attack.

An accurate, precise, and robust analytical method is required for measurements of heavy metals in foodstuffs to ensure regulatory compliance, maximum product safety and sustainability, and brand protection. The chosen technique must measure toxic elements, species, and micronutrients, and must also identify whether products have been contaminated during the production process or packaging or by the cooking utensils used to prepare them. Authenticity and origin determinations are also essential. Inductively coupled plasma mass spectrometry (ICP-MS) addresses all these requirements in the most efficient way.

Advantages of ICP-MS

To safeguard public health, global legislative bodies have introduced strict regulations that specify maximum allowable concentrations of heavy metals in foodstuffs.

ICP-MS is a high throughput, plasma-based technique with a single high-energy excitation source providing precise determination of heavy metals in foods. The multi-elemental and multi-isotopic nature of the method offers the potential to analyze a whole suite of elements in a single run, saving considerable time and money and allowing faster and more cost-effective decision-making. High linear dynamic range (LDR), another important feature, allows for the simultaneous detection of ultra trace and major elements in one run to obtain comprehensive information about the sample. Trace elements can be determined in a wide range of matrices from parts per trillion (ppt) to low percentage level.

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