Arsenic contamination of food and beverages has become a heated topic of discussion in media outlets and many households across the globe. Arsenic, like many other toxic analytes, exists in many forms, some of which are very toxic (As3+, As5+) while many others are inert. It has thus become very critical to identify the levels and types of species that exists in a particular sample in order to differentiate between the non-toxic and toxic species.  Since arsenic is monoisotopic and possesses a large number of polyatomic interferences, it is necessary to use a collision/reaction cell for accurate unbiased analysis. Two main methods exist for interference removal, collision mode and reaction mode. Collision mode, using kinetic energy discrimination (KED), allows for matrix-independent analysis achieving relatively low detection limits, ppt-ppb. Reaction mode of operation is highly dependent on the sample matrix. Collision/reaction cells allow for the entire ionized sample (matrix and analytes) to enter the cell. Since no control exists to what enters the cell, chemical reactions are largely uncontrolled and lead to side reactions and the formation of cluster ions, ultimately biasing the results.  Controlling what enters the cell is key to controlled chemical reactions thus allowing for accurate, precise and unbiased data in reaction mode. Triple Quad ICP-MS (ICP-QQQ) provides the capability of controlling what enters the cell using MS/MS technology by selecting a particular mass (single AMU) or a mass range via the control of the first quadrupole (Q1) located upstream from the collision/reaction cell. This mechanism gives the operator valuable information on what enters the cell. With this critical piece of information, it is then possible to perform controlled chemical reactions.  Here we will discuss the theory and operation of the ICP-QQQ with MS/MS technology and its relevance to analyses of toxic analytes in food and beverages.

Transforming ICP-MS technology: Advances in interference removal for accurate arsenic analysis in food and beverages

245th National Meeting (2013)

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