title: Using on-line solid phase extraction for in vivo speciation of diffusible ferrous and ferric iron in living rat brain extracellular fluid.
abstract: Exploration of brain extracellular non-protein-bound/diffusible iron species remains a critically important issue in investigations of free radical biology and neurodegenerative diseases. In this study, a facile sample pretreatment scheme, involving poly(vinyl chloride)-metal ion interactions as a selective extraction procedure, was optimized in conjunction with microdialysis (MD) sampling and inductively coupled plasma mass spectrometry (ICP-MS) in cool-plasma mode for in vivo online monitoring of rat brain extracellular Fe(II) and Fe(III) species. Optimization of the system provided detection limits in the range 0.9-6.9 μg Fe L-1, based on a 12-μL microdialysate, for the tested iron species; relative standard deviations of the signal intensities during 7.8 h of continuous measurement were less than 9.4%-sufficient to determine the basal concentrations of rat brain extracellular Fe(II) and Fe(III) species and to describe their dynamic actions. The method's applicability was verified through (i) spike analyses of offline-collected rat brain microdialysates, (ii) determination of the basal Fe(II) and Fe(III) concentrations of living rat brain extracellular fluids, and (iii) monitoring of the dynamic changes in the Fe(II) and Fe(III) concentrations in response to perfusion of a high-K+medium. This proposed sample pretreatment scheme, based on polymer-metal ion interactions and hyphenation to an MD sampling device and an ICP-MS system, appears to have great practicality for the online monitoring of rat brain extracellular diffusible iron species.
authors.affiliation: Department of Bioscience and Biotechnology, National Taiwan Ocean University, Keelung, 20224, Taiwan. Electronic address: chengkuan@mail.ntou.edu.tw.
authors.forename: Cheng-Kuan
authors.initials: CK
authors.lastname: Su
authors.affiliation: Department of Biomedical Engineering and Environmental Sciences, National Tsing-Hua University, Hsinchu, 30013, Taiwan.
authors.forename: Yi-Ting
authors.initials: YT
authors.lastname: Chen
authors.affiliation: Department of Biomedical Engineering and Environmental Sciences, National Tsing-Hua University, Hsinchu, 30013, Taiwan. Electronic address: ycsun@mx.nthu.edu.tw.
authors.forename: Yuh-Chang
authors.initials: YC
authors.lastname: Sun
mesh_terms: D000818:Animals; D001921:Brain; D045604:Extracellular Fluid / Q000737:chemistry*; D005290:Ferric Compounds / Q000032:analysis*; D005296:Ferrous Compounds / Q000032:analysis*; D007501:Iron; D051381:Rats; D052616:Solid Phase Extraction
chemical_list: D005290:Ferric Compounds; D005296:Ferrous Compounds; D007501:Iron
keywords: Brain extracellular fluid; Diffusible; Inductively coupled plasma mass spectrometry; Iron speciation; Packed minicolumn