Analysis of trace elements in the central nerve tissues with inductively coupled plasma-mass spectrometry

To investigate the roles of various elements in neurological disorders, multi-element analysis of limited quantities of samples in the central nervous system is required. Inductively coupled plasma-mass spectrometry (ICP-MS) analysis suits this requirement, but spectral and non-spectral interferences are inevitable. We studied correction methods for the non-spectral interferences by analyzing signals of 21 elements in various concentrations of HNO3 as well as 5 major elements (Na, K, P, Ca, and Cl). Using internal standards, the interferences caused by the major elements were corrected, but the interferences caused by HNO3 were impossible to correct for the elements with high ionization potentials. Thus, we decided to use a standard addition method to correct these interferences. The spectral interferences on Mn and Fe rising from HNO3 or major elements were compared with the signals of samples. Although the interferences on Mn were negligible, those on Fe were considerable and careful blank subtraction were needed. We measured concentrations of elements in the spinal cord of 4 controls and a patient with amyotrophic lateral sclerosis (ALS) using the standard addition method. The concentrations of Mn, Se, Fe, and Zn in the controls were nearly the same as previously reported values, whereas Mn concentrations in the ALS patient were higher.