Applicability of CIM® monolithic chromatography in nickel speciation analysis
Element speciation analysis requires an efficient and rapid separation of element species and their highly sensitive detection. In order to preserve the original species present in the sample and prevent any species conversion during analysis, fast separation is usually required. Due to fast and high resolution separation, the CIM monolithic chromatographic columns has been gradually introduced for separation of metal-biomolecule complexes.1-3
Nickel (Ni) is considered to be a non-essential element for humans, while the food we eat represents an important source of exposure to Ni. Its levels in food and drinks are normally low, but sensitive individuals may develop allergic reactions to Ni as a result of dietary consumption. Cocoa contains relatively high Ni concentrations. However, there is a lack of information about Ni speciation in cocoa.
The application describes separation of Ni species by assembling four weak CIM DEAE anion-exchange disks into a monolithic column. The concentrations of the Ni species eluted from the column were quantified by post-column isotope dilution inductively coupled plasma mass spectrometry (ID)-ICP-MS. The Ni binding ligands eluted under the chromatographic peaks were identified off-line by tandem electro spray mass spectrometry (ESI-MS-MS), scanning for negative ions.
The mild chromatographic conditions of the CIM DEAE disks preserved chemical species and enabled separation of negatively charged Ni complexes.4 NH4NO3 was chosen as eluent since it enabled separation of Ni species and is compatible with ICP-MS and mass spectrometry detectors.