Comparative imaging of P, S, Fe, Cu, Zn and C in thin sections of rat brain tumor as well as control tissues by laser ablation inductively coupled plasma mass spectrometry

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used for quantitative imaging of selected elements (P, S, Fe, Cu, Zn and C) in thin sections of rat brain samples (thickness 20 pm). The sample surface was scanned (raster area similar to 2 cm(2)) with a focused laser beam (wavelength 266 nm, diameter of laser crater 50 mu m, and irradiance X 10(9) W cm(-2)). The laser ablation system was coupled to a doublefocusing sector field. The possibility was evaluated of using carbon (via measurement of C-13(+)) as an internal standard element for imaging element distribution as part of this method. The LA-ICP-MS images obtained for P, S, Fe Cu and Zn were quantified using synthetically prepared matrixmatched laboratory standards. Depending on the sample analyzed, concentrations of Cu and Zn in the control, tissue were found to be in the range of 8-10 mu g g(-1) and 10-12 mu g g(-1), while in the tumor tissue these concentrations were in the range of 12-15 mu g g(-1) and 15-17 mu g g(-1) respectively. The measurements of P, S and Fe distribution revealed the depletion of these elements in tumor tissue. In all the samples, the shape of the tumor could be clearly distinguished from the surrounding healthy tissue by the depletion in carbon. Additional experiments were performed in order to study the influence of the water content of the analyzed tissue on the intensity signal of the analyte. The results of these measurements show the linear correlation (R-2 = 0.9604) between the intensity of analyte and amount of water in the sample. The growth of a brain tumor was thus studied for the first time by imaging mass spectrometry. (c) 2008 Published by Elsevier B.V.