A fast and automated separation and quantification method for bromine speciation in enzymatically digested DNA samples via IC-ICP-MS


C. Erbacher, N. Flothkötter, M. Macke, C. D. Quarles, M. Sperling, J. Müller, U. Karst

University of Münster, Institute for Inorganic and Analytical Chemistry, Corrensstr. 28/30, 48149 Münster

Recently, there has been a rising interest in using DNA in material sciences, which has led to the question of whether DNA is able to transfer electrical charges. This is of particular relevance for the implementation in nanotechnological applications like molecular wires. Therefore, a fast and automated separation and quantification method for bromide and the artificial nucleoside 5-bromo-2’-deoxyuridine (5-BrdU) via hyphenation of ion exchange chromatography (IC) and inductively coupled plasma-mass spectrometry (ICP-MS) is presented in this study. The analysis of these two species is relevant to monitor the transfer of electrons along metal-mediated DNA base pairs. 5-BrdU, which is implemented into the DNA sequence, releases bromide upon one electron reduction after efficient electron transfer along the DNA. The concentrations of 5-BrdU and bromide in enzymatically digested DNA samples can therefore be used as a marker for the efficiency of electron transfer along the DNA helix. A large number of samples was analyzed using an automated IC system. This platform enables time-efficient external calibration by inline dilution of a stock solution. Due to the fast separation of the two bromine species in less than 90 s, the developed method is suitable for screening applications with a multitude of samples. Despite the isobaric interferences and a low degree of ionization for bromine detection via ICP-MS the method has a limit of detection of 30 ng/L which is approximately an order of magnitude lower than a comparable method using reversed phase high performance liquid chromatography and ICP‑MS.