Quantitative imaging of zinc, copper and lead in three distinct regions of the human brain by laser ablation inductively coupled plasma mass spectrometry

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to determine the distribution of the trace elements zinc, copper and lead in insular, central and hippocampal areas of thin tissue sections (thickness 20 μm) through an entire human brain hemisphere. For the investigation of the tissue samples, a commercial laser ablation system was coupled to a double-focusing sector field ICP-MS. The regions of interest of healthy brain tissue (thickness 20 μm) were scanned (raster area ∼200 mm2) with a focused laser beam (wavelength 266 nm, diameter of laser crater 200 μm and laser power density 3 × 109 W cm−2). The ion intensities of 64Zn+, 63Cu+ and 208Pb+ were measured by LA-ICP-MS within the ablated area. For quantification purposes, matrix-matched laboratory standards were prepared by means of dosing of each analyte to the pieces of brain tissue. The mass spectrometric analysis yielded inhomogeneous and largely reciprocal distributions of Zn and Cu in the selected areas of investigated brain samples. The highest concentrations of Zn and Cu with the most distinct distribution pattern were found in the hippocampus (up to 15 μg g−1). In contrast to zinc and copper, for lead, a more homogeneous distribution throughout all regions examined was found at a low concentration (in the ng g−1 range) level within the analytical range of LA-ICP-MS.