Nickel speciation in cocoa infusions using monolithic chromatography - Post-column ID-ICP-MS and Q-TOF-MS

Food Chem. 2017 Sep 1;230:327-335. doi: 10.1016/j.foodchem.2017.03.050. Epub 2017 Mar 10.


Nickel (Ni) is considered to be a potentially harmful element for humans. Its levels in foodstuffs are normally low (below 0.2mgkg-1), but sensitive individuals may develop allergy to Ni as a result of dietary consumption. Cocoa contains relatively high Ni concentrations (around 3mgkg-1). Ni bioavailability, its role in the flavour of food and its potential impact on human health depends primarily on its chemical species. However, there is a lack of information about Ni speciation in cocoa. In this work Ni species were separated on a weak convective interaction media diethylamine (CIM DEAE) monolithic chromatographic column and quantified by the post-column isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS). The Ni binding ligands in the separated fractions were identified "off line" by quadrupole time-of-flight mass spectrometry (Q-TOF MS). Ni was found to be present in the cocoa infusions as Ni2+ and Ni-gluconate and Ni-citrate complexes.

Keywords: Cocoa infusions; Isotope dilution inductively coupled plasma mass spectrometry; Monolithic chromatography; Nickel speciation; Time-of-flight mass spectrometry.

MeSH terms

  • Chocolate / analysis*
  • Chromatography, High Pressure Liquid / methods*
  • Humans
  • Mass Spectrometry / methods*
  • Nickel / analysis
  • Nickel / chemistry*
  • Spectrum Analysis / methods*


  • Nickel