In trace elemental analysis, people are used to looking at concentrations of toxic elements to determine whether drinking water is safe, soils are free from contamination and pharmaceutical products are pure. In many cases, it is quite clear which level for a given element is “OK” and which is a “No Go.” However, some elements can appear in different chemical forms depending on what type of matrix they exist in, and to manage the distinction between them is not so easy. A good example for such a “smooth criminal” is arsenic, but also chromium or mercury may be potential suspects. For example, the element arsenic can be found in the environment as part of a geological location. The use of arsenic in pesticides and wood preservatives was phased out long ago, but traces of arsenic can still be found all over the world due to the broad distribution of these products.
Commonly, we perceive arsenic as toxic (and many classical crime stories support us in doing so), however, this element can be present in many different chemical forms, both inorganic (the weapon) and organic. An example of an organic arsenic is a compound called arsenobetaine, which may be formed through biological processes and is typically far less toxic, even less toxic than Aspirin. Hence, fish and sea food may contain high levels of total arsenic in a non-toxic form, whereas plants and plant-derived foods, such as rice, surface waters and soils may contain varying amounts of arsenic, but in a highly toxic form. In some cases, it may be acceptable to assume the worst case scenario and assume the entire amount of arsenic found in a given sample as inorganic, but in other cases it may be necessary to identify all compounds and quantify them individually.
Since inductively coupled plasma mass spectrometry (ICP-MS) — an element selective and highly sensitive detection system — is not able to distinguish between different chemical forms of a given element (being rather like John McClane than Lieutenant Columbo), it needs an appropriate separation technique to partner up with. Ideally suited for the separation of the different species is Ion Chromatography (IC). The combination of both techniques is a perfect match, since Ion Chromatography is capable of separating charged or polar compounds with narrow peak width, leading to lower limits of detection. In addition, it is essentially metal free, which means no collateral damage caused by the eluent, which can lead to increased ICP-MS background resulting in a loss in sensitivity. Just like Sherlock Holmes and Dr. Watson, this team is capable of unveiling the true identity of the arsenic compounds in your sample in a few minutes, and they have demonstrated their ability in a lot of complicated cases, for example, apple juice, rice or rice syrup.
So, if you’re worried about becoming a victim of the smooth criminal arsenic, just get in touch and find out how IC-ICP-MS may help you stay safe.