Determination of Mo and Mn in human brain samples by different techniques

Abstract

A study was undertaken to determine Mo and Mn concentrations in 5 different brain regions of 5 control and 5 Alzheimer's diseased (AD) patients. The main purpose of this work was to evaluate the performance of our analytical methods including sample preparation. Microwave-assisted digestion was used for sample dissolution. The digested samples were analyzed for Mo by ETAAS and ICP-MS. Low levels of Mo in the digested solutions (ng ml⁻¹) preclude the direct ETAAS analysis (LOD 0.75 ng ml⁻¹). This problem could be solved by preconcentration of Mo on an iminodiacetic acid ethyl-cellulose (IDAEC) chelating microcolumn. The optimal pH range of sorption is between 1.5 and 4. Our ICP-MS method is adequate for Mo determination in human brain samples using ⁹⁸Mo for the evaluation (LOD 0.05 ng ml⁻¹). The Mn content was determined applying ETAAS, ICP-MS, ICP-AES and NAA. The results of the different techniques were in good agreement. The techniques are compared in terms of accuracy, precision, detection limits, time and sample requirement. The accuracy of the measured data is investigated by the analysis of biological certified reference materials. The mean concentration of Mn in human brain samples is in the range 1.1–2.9 ppm, while for Mo it is between 90 and 330 ppb, for dry weight. Significantly higher values were found in the putamen and a difference in these concentrations between AD (c_Mo = 330 ± 42 ppb, c_Mn = 2.90 ± 0.07 ppm) and control patients (c_Mo = 219 ± 16 ppb, c_Mn = 2.40 ± 0.08 ppm).