Size characterization of manganese species from liver extracts using size exclusion chromatography inductively coupled plasma mass spectrometry

Increased Mn levels are known to damage the central nervous system, resulting in motoric abnormalities and psychic disorder and finally resulting even in symptoms similar to Parkinson's disease. Monomethyl-Mn-pentadienyl-tricarbonyl is used as anti-knock agent and consequently Mn compounds are exhausted into air from automobiles. With additional inhalative Mn exposure, finally an Mn overflow of the liver is known, resulting in increased Mn transport to other organs, predominantly to the brain. Specific Mn-species then seem to be generated in liver, however, their speciation is still not investigated. This paper focuses on experiments to get more information on Mn species with respect to a size characterization of the Mn species in liver. Liver extracts were analyzed using a mass calibrated size exclusion chromatography (SEC) column being coupled to inductively coupled plasma mass spectrometry (ICP-MS) detection. As an important prerequisite, the stability of Mn species in the liver extracts during storage was investigated as well. It turned out that short term storage of the extract (under Ar atmosphere) at 4 °C seems to be best suited. Storage for several days even at −20 °C demonstrated already considerable changes in species pattern. Further investigations focused on improvements in detection during hyphenation using dynamic reaction cell (DRC) technology for Mn detection. The signal to noise (S/N) ratio was increased up to a factor of 15 when using DRC technology compared to conventional ICP-MS without DRC. The analysis of liver extracts with a mass calibrated SEC column coupled to inductively coupled plasma-dynamic reaction cell-mass spectrometry (ICP-DRC-MS) showed Mn associated to ca. 36% to a peak covering a mass range 100-260 kDa, approximately 9% was found in a peak having the mass range 37-77 kDa, 46% in a peak having the mass range 13-36 kDa and ca. 7% in the low molecular mass (LMM) range.