Analysis and Speciation of Lanthanoides by ICP-MS

Abstract

Abstract Inductively coupled plasma mass spectrometry (ICP-MS) is based on formation of positively charged atomic ions in a high-frequency inductively coupled Argon plasma at atmospheric pressure. The ions are extracted and transferred from the plasma source into a mass analyzer operated at high vacuum via an interface equipped with a sampling and a skimmer cone. The ions are separated in the mass analyzer according to their charge to mass ratio. The ions are converted at a conversion dynode and are detected by use of a secondary electron multiplier or a Faraday cup. From an analytical point of view, ICP-MS is a well-established method for multi-elemental analysis in particular for elements at trace- and ultra-trace levels. Furthermore, methods based on ICP-MS offer simple quantification concepts, for which usually (liquid) standards are applied, low matrix effects compared to other conventional analytical techniques, and relative limits of detection (LODs) in the low pg g−1 range and absolute LODs down to the attomol range. For these applications, ICP-MS excels by a high sensitivity which is independent of the molecular structure and a wide linear dynamic range. It has found acceptance in various application areas and during the last decade ICP-MS is also more and more applied for detection of rare earth elements particularly in the life sciences. Due to the fact that all molecules introduced into the high temperature of the plasma in the ion source were completely dissociated and broken down into atoms, which are subsequently ionized, all elemental species information is completely lost. However, if the different species are separated before they enter the plasma by using adequate fractionation or separation techniques, then ICP-MS can be used as a very sensitive element-specific detector. We will discuss this feature of ICP-MS in this chapter in more detail at hand of the speciation of gadolinium-containing contrast agents.