HPLC-ICP-MS coupling and application to speciation

While the link between the essentiality and/or dangerousness of trace elements and the dose they contain has been known for a very long time, it has now been established that these beneficial or toxic effects are strongly linked to the physico-chemical form in which the element is present. As a result, recent regulations increasingly require the specific analysis of an element's chemical form, and less and less its total concentration. This is the case in fields of application such as the environment, food and certain industrial issues for elements such as chromium (hexavalent chromium) or arsenic (inorganic forms).

One of the most widely used techniques for analyzing the chemical forms of trace elements is the on-line coupling of separation by high-performance liquid chromatography (HPLC) with detection by inductively coupled plasma mass spectrometry (ICP-MS). This technique is becoming increasingly widespread in many laboratories, as it meets environmental, industrial and regulatory requirements, particularly in terms of analytical performance.

Several types of chemical or physical interactions can be used in HPLC to separate and thus analyze chemical forms of trace elements with very different physico-chemical properties. ICP-MS is a high-performance elemental detector that can achieve very low concentrations with good specificity.

In this article, the general principles of these two techniques (chromatographic modes and types of columns used, ICP-MS technology) are presented, followed by their coupling and its constraints (systems for introducing the eluent into the ICP-MS, problems inherent in the mobile phase, etc.). The separation and quantification of the different chemical forms (speciation analysis) of the most widely studied elements using HPLC-ICP-MS are detailed. Finally, protocols for controlling the quality of analyses using this coupling are described.