Quantitative Analysis of Iron in Biological Tissue Section by Isotope Dilution Laser Ablation Inductively Coupled Plasma-Mass Spectrometry

Traceable methods for the determination of total metal concentrations, as well as the regional spatial distribution (quantitative imaging) in biological tissues, are important to understand the pathogenesis and potential treatment of neurodegenerative diseases. Calibration strategies for quantitative analysis of trace elements in biological tissues sections have been reported earlier. However, their validation still remains a challenge due to the lack of suitable certified reference materials and primary methods for quantitative elemental analysis. In this work, a methodology based on isotope dilution calibration with laser ablation (LA) ICP-MS is, for the first time, developed for the accurate quantitative analysis of iron in thin sections of biological tissue. A novel approach was developed to determine the exact mass of spike (5' Fe) added to the tissue section. Different isotope exchange conditions and their effect on the achievement of isotopic equilibration were investigated. Assessment of the accuracy of the developed method for quantitative iron imaging of brain tissues by laser ablation-isotope dilution (LA-ID) -ICP-MS was performed by analysis of in-house prepared homogeneous sheep brain section and bovine liver NIST SRM (SRM 1577c) immobilized in gelatin. Total Fe analysis of in-house prepared standards by microwave digestion-ID-ICP-MS was also carried out and the Fe concentrations obtained using bulk and LA-ID-ICP-MS analysis were found to agree well. In the next step, the established method will be used for in-situ quantification of Fe in the mice brain section, which will help to explain the relationship of Fe distribution and some neurodegenerative diseases.