Manganese speciation using capillary electrophoresis–ICP-mass spectrometry

Manganese is a trace element known to activate many enzymes involved in metabolic processes and it shows protective function against oxidative stress. On the other hand, increased Mn levels are known for damaging the central nervous system, resulting in motoric abnormalities and psychic disorder. Such additional Mn exposure can cause an “Mn overflow” in the liver, accompanied by production of specific (labile) Mn transporters (Mn-species). The speciation of these Mn-compounds is still unknown but they are believed targeting the brain. The aim of this paper was to develop a speciation method for manganese species in liver extracts, which allows to speciate the compounds quickly and with minimal risk of species alteration. Capillary electrophoresis (CE)–inductively coupled plasma mass spectrometry (ICP-MS) offers a valuable tool as analytes are not in contact to a stationary phase which probably affects species stability. Separation usually is fast and ICP-MS detection is element specific and sensitive. The paper describes the set-up and optimization of the hyphenated technique, optimization of separation according to pH and finally the Mn speciation of a liver extract. Several Mn species were found, such as arginase, Mn-transferrine, Mn-albumine and some more. The detection limit of the method was determined at 1.1 μg Mn/L independent on the species.